Transcriptional changes during crown-root development and emergence in barley (Hordeum vulgare L.).

BACKGROUND: Roots play an important role during plant growth and development, ensuring water and nutrient uptake. Understanding the mechanisms regulating their initiation and development opens doors towards root system architecture engineering. RESULTS: Here, we investigated by RNA-seq analysis the changes in gene expression in the barley stem base of 1 day-after-germination (DAG) and 10DAG seedlings when crown roots are formed. We identified 2,333 genes whose expression was lower in the stem base of 10DAG seedlings compared to 1DAG seedlings. Those genes were mostly related to basal cellular activity such as cell cycle organization, protein biosynthesis, chromatin organization, cytoskeleton organization or nucleotide metabolism. In opposite, 2,932 genes showed up-regulation in the stem base of 10DAG seedlings compared to 1DAG seedlings, and their function was related to phytohormone action, solute transport, redox homeostasis, protein modification, secondary metabolism. Our results highlighted genes that are likely involved in the different steps of crown root formation from initiation to primordia differentiation and emergence, and revealed the activation of different hormonal pathways during this process. CONCLUSIONS: This whole transcriptomic study is the first study aiming at understanding the molecular mechanisms controlling crown root development in barley. The results shed light on crown root emergence that is likely associated with a strong cell wall modification, death of the cells covering the crown root primordium, and the production of defense molecules that might prevent pathogen infection at the site of root emergence.

Transcriptional Profiling of Early Defense Response to White Pine Blister Rust Infection in Pinus albicaulis (Whitebark Pine).

Pathogen perception generates the activation of signal transduction cascades to host defense. White pine blister rust (WPBR) is caused by Cronartium ribicola J.C. Fisch and affects a number of species of Pinus. One of the most severely affected species is Pinus albicaulis Engelm (whitebark pine). WPBR resistance in the species is a polygenic and complex trait that requires an optimized immune response. We identified early responses in 2-year-old seedlings after four days of fungal inoculation and compared the underlying transcriptomic response with that of healthy non-inoculated individuals. A de novo transcriptome assembly was constructed with 56,796 high quality-annotations derived from the needles of susceptible and resistant individuals in a resistant half-sib family. Differential expression analysis identified 599 differentially expressed transcripts, from which 375 were upregulated and 224 were downregulated in the inoculated seedlings. These included components of the initial phase of active responses to abiotic factors and stress regulators, such as those involved in the first steps of flavonoid biosynthesis. Four days after the inoculation, infected individuals showed an overexpression of chitinases, reactive oxygen species (ROS) regulation signaling, and flavonoid intermediates. Our research sheds light on the first stage of infection and emergence of disease symptoms among whitebark pine seedlings. RNA sequencing (RNA-seq) data encoding hypersensitive response, cell wall modification, oxidative regulation signaling, programmed cell death, and plant innate immunity were differentially expressed during the defense response against C. ribicola.

Widely-targeted metabolomics and transcriptomics identify metabolites associated with flowering regulation of Choy Sum.

Choy Sum, a stalk vegetable highly valued in East and Southeast Asia, is characterized by its rich flavor and nutritional profile. Metabolite accumulation is a key factor in Choy Sum stalk development; however, no research has focused on metabolic changes during the development of Choy Sum, especially in shoot tip metabolites, and their effects on growth and flowering. Therefore, in the present study, we used a widely targeted metabolomic approach to analyze metabolites in Choy Sum stalks at the seedling (S1), bolting (S3), and flowering (S5) stages. In total, we identified 493 metabolites in 31 chemical categories across all three developmental stages. We found that the levels of most carbohydrates and amino acids increased during stalk development and peaked at S5. Moreover, the accumulation of amino acids and their metabolites was closely related to G6P, whereas the expression of flowering genes was closely related to the content of T6P, which may promote flowering by upregulating the expressions of BcSOC1, BcAP1, and BcSPL5. The results of this study contribute to our understanding of the relationship between the accumulation of stem tip substances during development and flowering and of the regulatory mechanisms of stalk development in Choy Sum and other related species.

Identification and validation of stable reference genes for RT-qPCR analyses of Kobresia littledalei seedlings.

BACKGROUND: Kobreisa littledalei, belonging to the Cyperaceae family is the first Kobresia species with a reference genome and the most dominant species in Qinghai-Tibet Plateau alpine meadows. It has several resistance genes which could be used to breed improved crop varieties. Reverse Transcription Quantitative Real-Time Polymerase Chain Reaction (RT-qPCR) is a popular and accurate gene expression analysis method. Its reliability depends on the expression levels of reference genes, which vary by species, tissues and environments. However, K.littledalei lacks a stable and normalized reference gene for RT-qPCR analysis. RESULTS: The stability of 13 potential reference genes was tested and the stable reference genes were selected for RT-qPCR normalization for the expression analysis in the different tissues of K. littledalei under two abiotic stresses (salt and drought) and two hormonal treatments (abscisic acid (ABA) and gibberellin (GA)). Five algorithms were used to assess the stability of putative reference genes. The results showed a variation amongst the methods, and the same reference genes showed tissue expression differences under the same conditions. The stability of combining two reference genes was better than a single one. The expression levels of ACTIN were stable in leaves and stems under normal conditions, in leaves under drought stress and in roots under ABA treatment. The expression of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) expression was stable in the roots under the control conditions and salt stress and in stems exposed to drought stress. Expression levels of superoxide dismutase (SOD) were stable in stems of ABA-treated plants and in the roots under drought stress. Moreover, RPL6 expression was stable in the leaves and stems under salt stress and in the stems of the GA-treated plants. EF1-alpha expression was stable in leaves under ABA and GA treatments. The expression levels of 28 S were stable in the roots under GA treatment. In general, ACTIN and GAPDH could be employed as housekeeping genes for K. littledalei under different treatments. CONCLUSION: This study identified the best RT-qPCR reference genes for different K. littledalei tissues under five experimental conditions. ACTIN and GAPDH genes can be employed as the ideal housekeeping genes for expression analysis under different conditions. This is the first study to investigate the stable reference genes for normalized gene expression analysis of K. littledalei under different conditions. The results could aid molecular biology and gene function research on Kobresia and other related species.

Seeds Priming with Melatonin Improves Root Hydraulic Conductivity of Wheat Varieties under Drought, Salinity, and Combined Stress.

Drought and salinity stress reduce root hydraulic conductivity of plant seedlings, and melatonin application positively mitigates stress-induced damage. However, the underlying effect of melatonin priming on root hydraulic conductivity of seedlings under drought-salinity combined remains greatly unclear. In the current report, we investigated the influence of seeds of three wheat lines' 12 h priming with 100 µM of melatonin on root hydraulic conductivity (Lpr) and relevant physiological indicators of seedlings under PEG, NaCl, and PEG + NaCl combined stress. A previous study found that the combined PEG and NaCl stress remarkably reduced the Lpr of three wheat varieties, and its value could not be detected. Melatonin priming mitigated the adverse effects of combined PEG + NaCl stress on Lpr of H4399, Y1212, and X19 to 0.0071 mL·h-1·MPa-1, 0.2477 mL·h-1·MPa-1, and 0.4444 mL·h-1·MPa-1, respectively, by modulating translation levels of aquaporin genes and contributed root elongation and seedlings growth. The root length of H4399, Y1212, and X19 was increased by 129.07%, 141.64%, and 497.58%, respectively, after seeds pre-treatment with melatonin under PEG + NaCl combined stress. Melatonin -priming appreciably regulated antioxidant enzyme activities, reduced accumulation of osmotic regulators, decreased levels of malondialdehyde (MDA), and increased K+ content in stems and root of H4399, Y1212, and X19 under PEG + NaCl stress. The path investigation displayed that seeds primed with melatonin altered the modification of the path relationship between Lpr and leaf area under stress. The present study suggested that melatonin priming was a strategy as regards the enhancement of root hydraulic conductivity under PEG, NaCl, and PEG + NaCl stress, which efficiently enhanced wheat resistant to drought-salinity stress.

Apple-arbuscular mycorrhizal symbiosis confers resistance to Fusarium solani by inducing defense response and elevating nitrogen absorption.

Fusarium solani exerts detrimental effects on plant growth, which is one of the reasons for the incidence of apple replant disease. Arbuscular mycorrhizal fungi (AMF) enhance plant resistance to Fusarium wilt; however, the mechanism remains poorly understood. Therefore, the present study investigated the symbiosis between apple and AMF and explored the physiology, especially nitrate metabolism, antioxidant defense, and photosynthetic performance, when infected by F. solani. The experiment was carried out with four treatments, namely -AMF - F. solani, -AMF + F. solani, -AMF + F. solani, and + AMF + F. solani. In this study, the -AMF + F. solani treatment increased the activity of enzymes associated with nitrogen metabolism, such as the nitrate and nitrite reductases, in the apple root system. The +AMF + F. solani treatment showed higher antioxidant enzyme activities than the -AMF + F. solani by F. solani infection. The apple seedlings of the +AMF + F. solani treatment decreased reactive oxygen accumulation and reduced the oxidative damages triggered by F. solani infection. The improvement in antioxidant capacity due to the +AMF + F. solani treatment was closely associated with the upregulation of genes related to the antioxidant system. The F. solani infection greatly damaged the photosynthetic process, while the +AMF + F. solani treatment significantly improved it compared to the -AMF + F. solani treatment. In conclusion, the study demonstrated that the apple-AMF symbiosis plays an active role in regulating the resistance against F. solani infection by enhancing defense response and nitrogen metabolism.

Genome-wide association study for seedling heat tolerance under two temperature conditions in bread wheat (Triticum aestivum L.).

BACKGROUND: As the greenhouse effect intensifies, global temperatures are steadily increasing, posing a challenge to bread wheat (Triticum aestivum L.) production. It is imperative to comprehend the mechanism of high temperature tolerance in wheat and implement breeding programs to identify and develop heat-tolerant wheat germplasm and cultivars. RESULTS: To identify quantitative trait loci (QTL) related to heat stress tolerance (HST) at seedling stage in wheat, a panel of 253 wheat accessions which were re-sequenced used to conduct genome-wide association studies (GWAS) using the factored spectrally transformed linear mixed models (FaST-LMM). For most accessions, the growth of seedlings was found to be inhibited under heat stress. Analysis of the phenotypic data revealed that under heat stress conditions, the main root length, total root length, and shoot length of seedlings decreased by 47.46%, 49.29%, and 15.19%, respectively, compared to those in normal conditions. However, 17 varieties were identified as heat stress tolerant germplasm. Through GWAS analysis, a total of 115 QTLs were detected under both heat stress and normal conditions. Furthermore, 15 stable QTL-clusters associated with heat response were identified. By combining gene expression, haplotype analysis, and gene annotation information within the physical intervals of the 15 QTL-clusters, two novel candidate genes, TraesCS4B03G0152700/TaWRKY74-B and TraesCS4B03G0501400/TaSnRK3.15-B, were responsive to temperature and identified as potential regulators of HST in wheat at the seedling stage. CONCLUSIONS: This study conducted a detailed genetic analysis and successfully identified two genes potentially associated with HST in wheat at the seedling stage, laying a foundation to further dissect the regulatory mechanism underlying HST in wheat under high temperature conditions. Our finding could serve as genomic landmarks for wheat breeding aimed at improving adaptation to heat stress in the face of climate change.

Root system architecture variation among barley (Hordeum vulgare L.) accessions at seedling stage under soil acidity condition.

MAIN CONCLUSION: Soil acidity in Ethiopian highlands impacts barley production, affecting root system architecture. Study on 300 accessions showed significant trait variability, with potential for breeding enhancement. Soil acidity poses a significant challenge to crop production in the highland regions of Ethiopia, particularly impacting barley, a crucial staple crop. This acidity serves as a key stressor affecting the root system architecture (RSA) of this crop. Hence, the objective of this study was to assess the RSA traits variability under acidic soil conditions using 300 barley accessions in a greenhouse experiment. The analysis of variance indicated substantial variations among the accessions across all traits studied. The phenotypic coefficient of variation ranged from 24.4% for shoot dry weight to 11.1% for root length, while the genotypic coefficient variation varied between 18.83 and 9.2% for shoot dry weight and root length, respectively. The broad-sense heritability ranged from 36.7% for leaf area to 69.9% for root length, highlighting considerable heritability among multiple traits. The genetic advances as a percent of the mean ranged from 13.63 to 29.9%, suggesting potential for enhancement of these traits through breeding efforts. Principal component analysis and cluster analysis grouped the genotypes into two major clusters, each containing varying numbers of genotypes with contrasting traits. This diverse group presents an opportunity to access a wide range of potential parent candidates to enhance genetic variablity in breeding programs. The Pearson correlation analysis revealed significant negative associations between root angle (RA) and other RSA traits. This helps indirect selection of accessions for further improvement in soil acidity. In conclusion, this study offers valuable insights into the RSA characteristics of barley in acidic soil conditions, aiding in the development of breeding strategies to enhance crop productivity in acidic soil environments.

Silicon regulates phosphate deficiency through involvement of auxin and nitric oxide in barley roots.

MAIN CONCLUSION: Silicon application mitigates phosphate deficiency in barley through an interplay with auxin and nitric oxide, enhancing growth, photosynthesis, and redox balance, highlighting the potential of silicon as a fertilizer for overcoming nutritional stresses. Silicon (Si) is reported to attenuate nutritional stresses in plants, but studies on the effect of Si application to plants grown under phosphate (Pi) deficiency are still very scarce, especially in barley. Therefore, the present work was undertaken to investigate the potential role of Si in mitigating the adverse impacts of Pi deficiency in barley Hordeum vulgare L. (var. BH902). Further, the involvement of two key regulatory signaling molecules--auxin and nitric oxide (NO)--in Si-induced tolerance against Pi deficiency in barley was tested. Morphological attributes, photosynthetic parameters, oxidative stress markers (O2·-, H2O2, and MDA), antioxidant system (enzymatic--APX, CAT, SOD, GR, DHAR, MDHAR as well as non-enzymatic--AsA and GSH), NO content, and proline metabolism were the key traits that were assessed under different treatments. The P deficiency distinctly declined growth of barley seedlings, which was due to enhancement in oxidative stress leading to inhibition of photosynthesis. These results were also in parallel with an enhancement in antioxidant activity, particularly SOD and CAT, and endogenous proline level and its biosynthetic enzyme (P5CS). The addition of Si exhibited beneficial effects on barley plants grown in Pi-deficient medium as reflected in increased growth, photosynthetic activity, and redox balance through the regulation of antioxidant machinery particularly ascorbate-glutathione cycle. We noticed that auxin and NO were also found to be independently participating in Si-mediated improvement of growth and other parameters in barley roots under Pi deficiency. Data of gene expression analysis for PHOSPHATE TRANSPORTER1 (HvPHT1) indicate that Si helps in increasing Pi uptake as per the need of Pi-deficient barley seedlings, and also auxin and NO both appear to help Si in accomplishing this task probably by inducing lateral root formation. These results are suggestive of possible application of Si as a fertilizer to correct the negative effects of nutritional stresses in plants. Further research at genetic level to understand Si-induced mechanisms for mitigating Pi deficiency can be helpful in the development of new varieties with improved tolerance against Pi deficiency, especially for cultivation in areas with Pi-deficient soils.

The tetraploid wheat (Triticum dicoccum (Schrank) Schuebl.) improves nitrogen uptake and assimilation adaptation to nitrogen-deficit stress.

MAIN CONCLUSION: The genetic diversity in tetraploid wheat provides a genetic pool for improving wheat productivity and environmental resilience. The tetraploid wheat had strong N uptake, translocation, and assimilation capacity under N deficit stress, thus alleviating growth inhibition and plant N loss to maintain healthy development and adapt to environments with low N inputs. Tetraploid wheat with a rich genetic variability provides an indispensable genetic pool for improving wheat yield. Mining the physiological mechanisms of tetraploid wheat in response to nitrogen (N) deficit stress is important for low-N-tolerant wheat breeding. In this study, we selected emmer wheat (Kronos, tetraploid), Yangmai 25 (YM25, hexaploid), and Chinese spring (CS, hexaploid) as materials. We investigated the differences in the response of root morphology, leaf and root N accumulation, N uptake, translocation, and assimilation-related enzymes and gene expression in wheat seedlings of different ploidy under N deficit stress through hydroponic experiments. The tetraploid wheat (Kronos) had stronger adaptability to N deficit stress than the hexaploid wheats (YM25, CS). Kronos had better root growth under low N stress, expanding the N uptake area and enhancing N uptake to maintain higher NO3- and soluble protein contents. Kronos exhibited high TaNRT1.1, TaNRT2.1, and TaNRT2.2 expression in roots, which promoted NO3- uptake, and high TaNRT1.5 and TaNRT1.8 expression in roots and leaves enhanced NO3- translocation to the aboveground. NR and GS activity in roots and leaves of Kronos was higher by increasing the expression of TANIA2, TAGS1, and TAGS2, which enhanced the reduction and assimilation of NO3- as well as the re-assimilation of photorespiratory-released NH4+. Overall, Kronos had strong N uptake, translocation, and assimilation capacity under N deficit stress, alleviating growth inhibition and plant N loss and thus maintaining a healthy development. This study reveals the physiological mechanisms of tetraploid wheat that improve nitrogen uptake and assimilation adaptation under low N stress, which will provide indispensable germplasm resources for elite low-N-tolerant wheat improvement and breeding.

Regulatory mechanisms used by ZmMYB39 to enhance drought tolerance in maize (Zea mays) seedlings.

Drought is a significant abiotic stressor that limits maize (Zea mays L.) growth and development. Thus, enhancing drought tolerance is critical for promoting maize production. Our findings demonstrated that ZmMYB39 is an MYB transcription factor with transcriptional activation activity. Drought stress experiments involving ZmMYB39 overexpression and knockout lines indicated that ZmMYB39 positively regulated drought stress tolerance in maize. DAP-Seq, EMSA, dual-LUC, and RT-qPCR provided initial insights into the molecular regulatory mechanisms by which ZmMYB39 enhances drought tolerance in maize. ZmMYB39 directly promoted the expression of ZmP5CS1, ZmPOX1, ZmSOD2, ZmRD22, ZmNAC49, and ZmDREB2A, which are involved in stress resistance. ZmMYB39 enhanced drought tolerance by interacting with and promoting the expression of ZmFNR1, ZmHSP20, and ZmDOF6. Our study offers a theoretical basis for understanding the molecular regulatory networks involved in maize drought stress response. Furthermore, ZmMYB39 serves as a valuable genetic resource for breeding drought-resistant maize.

Temperature-Caused Changes in Raman Pattern and Protein Profiles of Winter Triticale (x Triticosecale, Wittm.) Field-Grown Seedlings.

Climate change, which causes periods with relatively high temperatures in winter in Poland, can lead to a shortening or interruption of the cold hardening of crops. Previous research indicates that cold acclimation is of key importance in the process of acquiring cereal tolerance to stress factors. The objective of this work was to verify the hypothesis that both natural temperature fluctuations and the plant genotype influence the content of metabolites as well as proteins, including antioxidant enzymes and photosystem proteins. The research material involved four winter triticale genotypes, differing in their tolerance to stress under controlled conditions. The values of chlorophyll a fluorescence parameters and antioxidant activity were measured in their seedlings. Subsequently, the contribution of selected proteins was verified using specific antibodies. In parallel, the profiling of the contents of chlorophylls, carotenoids, phenolic compounds, and proteins was carried out by Raman spectroscopy. The obtained results indicate that a better PSII performance along with a higher photosystem II proteins content and thioredoxin reductase abundance were accompanied by a higher antioxidant activity in the field-grown triticale seedlings. The Raman studies showed that the cold hardening led to a variation in photosynthetic dyes and an increase in the phenolic to carotenoids ratio in all DH lines.

Azolla filiculoides extract improved salt tolerance in wheat (Triticum aestivum L.) is associated with prompting osmostasis, antioxidant potential and stress-interrelated genes.

The growth and productivity of crop plants are negatively affected by salinity-induced ionic and oxidative stresses. This study aimed to provide insight into the interaction of NaCl-induced salinity with Azolla aqueous extract (AAE) regarding growth, antioxidant balance, and stress-responsive genes expression in wheat seedlings. In a pot experiment, wheat kernels were primed for 21 h with either deionized water or 0.1% AAE. Water-primed seedlings received either tap water, 250 mM NaCl, AAE spray, or AAE spray + NaCl. The AAE-primed seedlings received either tap water or 250 mM NaCl. Salinity lowered growth rate, chlorophyll level, and protein and amino acids pool. However, carotenoids, stress indicators (EL, MDA, and H2O2), osmomodulators (sugars, and proline), antioxidant enzymes (CAT, POD, APX, and PPO), and the expression of some stress-responsive genes (POD, PPO and PAL, PCS, and TLP) were significantly increased. However, administering AAE contributed to increased growth, balanced leaf pigments and assimilation efficacy, diminished stress indicators, rebalanced osmomodulators and antioxidant enzymes, and down-regulation of stress-induced genes in NaCl-stressed plants, with priming surpassing spray in most cases. In conclusion, AAE can be used as a green approach for sustaining regular growth and metabolism and remodelling the physio-chemical status of wheat seedlings thriving in salt-affected soils.

Maize miRNAs and their putative target genes involved in chilling stress response in 5-day old seedlings.

BACKGROUND: In the context of early sowing of maize as a promising adaptation strategy that could significantly reduce the negative effects of climate change, an in-depth understanding of mechanisms underlying plant response to low-temperature stress is demanded. Although microRNAs (miRNAs) have been recognized as key regulators of plant stress response, research on their role in chilling tolerance of maize during early seedling stages is scarce. Therefore, it is of great significance to explore chilling-responsive miRNAs, reveal their expression patterns and associated target genes, as well as to examine the possible functions of the conserved and novel miRNAs. In this study, the role of miRNAs was examined in 5d-old maize seedlings of one tolerant and one sensitive inbred line exposed to chilling (10/8 °C) stress for 6 h and 24 h, by applying high throughput sequencing. RESULTS: A total of 145 annotated known miRNAs belonging to 30 families and 876 potentially novel miRNAs were identified. Differential expression (DE) analysis between control and stress conditions identified 98 common miRNAs for both genotypes at one time point and eight miRNAs at both time points. Target prediction and enrichment analysis showed that the DE zma-miR396, zma-miR156, zma-miR319, and zma-miR159 miRNAs modulate growth and development. Furthermore, it was found that several other DE miRNAs were involved in abiotic stress response: antioxidative mechanisms (zma-miR398), signal transduction (zma-miR156, zma-miR167, zma-miR169) and regulation of water content (zma-miR164, zma-miR394, zma-miR396). The results underline the zma-miRNAs involvement in the modulation of their target genes expression as an important aspect of the plant's survival strategy and acclimation to chilling stress conditions. CONCLUSIONS: To our understanding, this is the first study on miRNAs in 5-d old seedlings' response to chilling stress, providing data on the role of known and novel miRNAs post-transcriptional regulation of expressed genes and contributing a possible platform for further network and functional analysis.

Utilizing transcriptomics and proteomics to unravel key genes and proteins of Oryza sativa seedlings mediated by selenium in response to cadmium stress.

BACKGROUND: Cadmium (Cd) pollution has declined crop yields and quality. Selenium (Se) is a beneficial mineral element that protects plants from oxidative damage, thereby improving crop tolerance to heavy metals. The molecular mechanism of Se-induced Cd tolerance in rice (Oryza sativa) is not yet understood. This study aimed to elucidate the beneficial mechanism of Se (1 mg/kg) in alleviating Cd toxicity in rice seedlings. RESULTS: Exogenous selenium addition significantly improved the toxic effect of cadmium stress on rice seedlings, increasing plant height and fresh weight by 20.53% and 34.48%, respectively, and increasing chlorophyll and carotenoid content by 16.68% and 15.26%, respectively. Moreover, the MDA, ·OH, and protein carbonyl levels induced by cadmium stress were reduced by 47.65%, 67.57%, and 56.43%, respectively. Cell wall metabolism, energy cycling, and enzymatic and non-enzymatic antioxidant systems in rice seedlings were significantly enhanced. Transcriptome analysis showed that the expressions of key functional genes psbQ, psbO, psaG, psaD, atpG, and PetH were significantly up-regulated under low-concentration Se treatment, which enhanced the energy metabolism process of photosystem I and photosystem II in rice seedlings. At the same time, the up-regulation of LHCA, LHCB family, and C4H1, PRX, and atp6 functional genes improved the ability of photon capture and heavy metal ion binding in plants. Combined with proteome analysis, the expression of functional proteins OsGSTF1, OsGSTU11, OsG6PDH4, OsDHAB1, CP29, and CabE was significantly up-regulated under Se, which enhanced photosynthesis and anti-oxidative stress mechanism in rice seedlings. At the same time, it regulates the plant hormone signal transduction pathway. It up-regulates the expression response process of IAA, ABA, and JAZ to activate the synergistic effect between each cell rapidly and jointly maintain the homeostasis balance. CONCLUSION: Our results revealed the regulation process of Se-mediated critical metabolic pathways, functional genes, and proteins in rice under cadmium stress. They provided insights into the expression rules and dynamic response process of the Se-mediated plant resistance mechanism. This study provided the theoretical basis and technical support for crop safety in cropland ecosystems and cadmium-contaminated areas.

Transcriptome analysis of antioxidant system response in Styrax tonkinensis seedlings under flood-drought abrupt alternation.

BACKGROUND: Styrax tonkinensis (Pierre) Craib ex Hartwich faces challenges in expanding in the south provinces of Yangtze River region due to climate extremes like flood-drought abrupt alternation (FDAA) caused by global warming. Low tolerance to waterlogging and drought restricts its growth in this area. To study its antioxidant system and molecular response related to the peroxisome pathway under FDAA, we conducted experiments on two-year-old seedlings, measuring growth indexes, reactive oxygen species content, antioxidant enzyme activity, and analyzing transcriptomes under FDAA and drought (DT) conditions. RESULTS: The physiological results indicated a reduction in water content in roots, stems, and leaves under FDAA conditions. The most significant water loss, amounting to 15.53% was observed in the leaves. Also, ROS accumulation was predominantly observed in leaves rather than roots. Through transcriptome analysis, we assembled a total of 1,111,088 unigenes (with a total length of 1,111,628,179 bp). Generally, SOD1 and CAT genes in S. tonkinensis seedlings were up-regulated to scavenge ROS. Conversely, the MPV17 gene exhibited contrasting reaction with up-regulation in leaves and down-regulation in roots, leading to increased ROS accumulation in leaves. CHS and F3H were down-regulated, which did not play an essential role in scavenging ROS. Moreover, the down-regulation of PYL, CPK and CALM genes in leaves may not contribute to stomatal closure, thereby causing continuous water loss through transpiration. Whereas, the decreased root vigor during the waterlogging phase and up-regulated CPK and CALM in roots posed obstacles to water absorption by roots. Additionally, the DEGs related to energy metabolism, including LHCA and LHCB, were negatively regulated. CONCLUSIONS: The ROS generation triggered by MPV17 genes was not the main reason for the eventual mortality of the plant. Instead, plant mortality may be attributed to water loss during the waterlogging phase, decreased root water uptake capacity, and continued water loss during the subsequent drought period. This study establishes a scientific foundation for comprehending the morphological, physiological, and molecular facts of S. tonkinensis under FDAA conditions.

Limited intraspecific variation in drought resistance along a pronounced tropical rainfall gradient.

Assessing within-species variation in response to drought is crucial for predicting species' responses to climate change and informing restoration and conservation efforts, yet experimental data are lacking for the vast majority of tropical tree species. We assessed intraspecific variation in response to water availability across a strong rainfall gradient for 16 tropical tree species using reciprocal transplant and common garden field experiments, along with measurements of gene flow and key functional traits linked to drought resistance. Although drought resistance varies widely among species in these forests, we found little evidence for within-species variation in drought resistance. For the majority of functional traits measured, we detected no significant intraspecific variation. The few traits that did vary significantly between drier and wetter origins of the same species all showed relationships opposite to expectations based on drought stress. Furthermore, seedlings of the same species originating from drier and wetter sites performed equally well under drought conditions in the common garden experiment and at the driest transplant site. However, contrary to expectation, wetter-origin seedlings survived better than drier-origin seedlings under wetter conditions in both the reciprocal transplant and common garden experiment, potentially due to lower insect herbivory. Our study provides the most comprehensive picture to date of intraspecific variation in tropical tree species' responses to water availability. Our findings suggest that while drought plays an important role in shaping species composition across moist tropical forests, its influence on within-species variation is limited.

Genetic mapping of loci affecting seedling and adult-plant resistance to powdery mildew derived from two CIMMYT wheat lines.

MAIN CONCLUSION: PM3 and PM8 alleles carried by two CIMMYT wheat lines confer powdery mildew resistance in seedlings and/or adult plants. A stage-specific epistatic interaction was observed between PM3 and PM8. Powdery mildew is an important foliar disease of wheat. Major genes for resistance, which have been widely used in wheat breeding programs, are typically effective against only limited numbers of virulence genes of the pathogen. The main aim of this study was to map resistance loci in wheat lines 7HRWSN58 and ZWW09-149 from the International Maize and Wheat Improvement Center (CIMMYT). Doubled haploid populations (Magenta/7HRWSN58 and Emu Rock/ZWW09-149) were developed and grown in controlled environment experiments and inoculated with a composite of Blumeria graminis f.sp. tritici isolates that had been collected at various locations in Western Australia. Plants were assessed for powdery mildew symptoms (percentage leaf area diseased) on seedlings and adult plants. Populations were subjected to genotyping-by-sequencing and assayed for known SNPs in the resistance gene PM3. Linkage maps were constructed, and markers were anchored to the wheat reference genome sequence. In both populations, there were asymptomatic lines that exhibited no symptoms. Among symptomatic lines, disease severity varied widely. In the Magenta/7HRWSN58 population, most of the observed variation was attributed to the PM3 region of chromosome 1A, with the allele from 7HRWSN58 conferring resistance in seedlings and adult plants. In the Emu Rock/ZWW09-149 population, two interacting quantitative trait loci were mapped: one at PM3 and the other on chromosome 1B. The Emu Rock/ZWW09-149 population was confirmed to segregate for a 1BL·1RS translocation that carries the PM8 powdery mildew resistance gene from rye. Consistent with previous reports that PM8-derived resistance can be suppressed by PM3 alleles, the observed interaction between the quantitative trait loci on chromosomes 1A and 1B indicated that the PM3 allele carried by ZWW09-149 suppresses PM8-derived resistance from ZWW09-149, but only at the seedling stage. In adult plants, the PM8 region conferred resistance regardless of the PM3 genotype. The resistance sources and molecular markers that were investigated here could be useful in wheat breeding.

Overexpression of VaBAM3 from Vitis amurensis enhances seedling cold tolerance by promoting soluble sugar accumulation and reactive oxygen scavenging.

KEY MESSAGE: The VaBAM3 cloned from Vitis amurensis can enhance the cold tolerance of overexpressed plants, but VaBAM3 knock out by CRISPR/Cas9 system weakened grape callus cold tolerance. In grape production, extreme cold conditions can seriously threaten plant survival and fruit quality. Regulation of starch content by ß-amylase (BAM, EC: 3.2.1.2) contributes to cold tolerance in plants. In this study, we cloned the VaBAM3 gene from an extremely cold-tolerant grape, Vitis amurensis, and overexpressed it in tomato and Arabidopsis plants, as well as in grape callus for functional characterization. After exposure to cold stress, leaf wilting in the VaBAM3-overexpressing tomato plants was slightly less pronounced than that in wild-type tomato plants, and these plants were characterized by a significant accumulation of autophagosomes. Additionally, the VaBAM3-overexpressing Arabidopsis plants had a higher freezing tolerance than the wild-type counterparts. Under cold stress conditions, the activities of total amylase, BAM, peroxidase, superoxide dismutase, and catalase in VaBAM3-overexpressing plants were significantly higher than those in the corresponding wild-type plants. Furthermore, sucrose, glucose, and fructose contents in these lines were similarly significantly higher, whereas starch contents were reduced in comparison to the levels in the wild-type plants. Furthermore, we detected high CBF and COR gene expression levels in cold-stressed VaBAM3-overexpressing plants. Compared with those in VaBAM3-overexpressing grape callus, the aforementioned indicators tended to change in the opposite direction in grape callus with silenced VaBAM3. Collectively, our findings indicate that heterologous overexpression of VaBAM3 enhanced cold tolerance of plants by promoting the accumulation of soluble sugars and scavenging of excessive reactive oxygen species. These findings provide a theoretical basis for the cultivation of cold-resistant grape and support creation of germplasm resources for this purpose.

The conversion of monolignans to sesquilignans and dilignans is closely correlated to the regulation of Arctium lappa seed germination.

MAIN CONCLUSION: The secondary metabolic conversion of monolignans to sesquilignans/dilignans was closely related to seed germination and seedling establishment in Arctium lappa. Arctium lappa plants are used as a kind of traditional Chinese medicines for nearly 1500 years, and so far, only a few studies have put focus on the key secondary metabolic changes during seed germination and seedling establishment. In the current study, a combined approach was used to investigate the correlation among secondary metabolites, plant hormone signaling, and transcriptional profiles at the early critical stages of A. lappa seed germination and seedling establishment. Of 50 metabolites in methonolic extracts of A. lappa samples, 35 metabolites were identified with LC-MS/MS and 15 metabolites were identified with GC-MS. Their qualitative properties were examined according to the predicted chemical structures. The quantitative analysis was performed for deciphering their metabolic profiles, discovering that the secondary metabolic conversion from monolignans to sesquilignans/dilignans was closely correlated to the initiation of A. lappa seed germination and seedling establishment. Furthermore, the critical transcriptional changes in primary metabolisms, translational regulation at different cellular compartments, and multiple plant hormone signaling pathways were revealed. In addition, the combined approach provides unprecedented insights into key regulatory mechanisms in both gene transcription and secondary metabolites besides many known primary metabolites during seed germination of an important traditional Chinese medicinal plant species. The results not only provide new insights to understand the regulation of key medicinal components of 'ARCTII FRUCTUS', arctiin and arctigenin at the stages of seed germination and seedling establishment, but also potentially spur the development of seed-based cultivation in A. lappa plants.