Aspartyl tRNA-synthetase (AspRS) gene family enhances drought tolerance in poplar through BABA-PtrIBIs-PtrVOZ signaling module.

BACKGROUND: Drought stress is a prevalent abiotic stress that significantly hinders the growth and development of plants. According to studies, ß-aminobutyric acid (BABA) can influence the ABA pathway through the AtIBI1 receptor gene to enhance cold resistance in Arabidopsis. However, the Aspartate tRNA-synthetase (AspRS) gene family, which acts as the receptor for BABA, has not yet been investigated in poplar. Particularly, it is uncertain how the AspRS gene family (PtrIBIs)r can resist drought stress after administering various concentrations of BABA to poplar. RESULTS: In this study, we have identified 12 AspRS family genes and noted that poplar acquired four PtrIBI pairs through whole genome duplication (WGD). We conducted cis-action element analysis and found a significant number of stress-related action elements on different PtrIBI genes promoters. The expression of most PtrIBI genes was up-regulated under beetle and mechanical damage stresses, indicating their potential role in responding to leaf damage stress. Our results suggest that a 50 mM BABA treatment can alleviate the damage caused by drought stress in plants. Additionally, via transcriptome sequencing, we observed that the partial up-regulation of BABA receptor genes, PtrIBI2/4/6/8/11, in poplars after drought treatment. We hypothesize that poplar responds to drought stress through the BABA-PtrIBIs-PtrVOZ coordinated ABA signaling pathway. Our research provides molecular evidence for understanding how plants respond to drought stress through external application of BABA. CONCLUSIONS: In summary, our study conducted genome-wide analysis of the AspRS family of P. trichocarpa and identified 12 PtrIBI genes. We utilized genomics and bioinformatics to determine various characteristics of PtrIBIs such as chromosomal localization, evolutionary tree, gene structure, gene doubling, promoter cis-elements, and expression profiles. Our study found that certain PtrIBI genes are regulated by drought, beetle, and mechanical damage implying their crucial role in enhancing poplar stress tolerance. Additionally, we observed that external application of low concentrations of BABA increased plant drought resistance under drought stress. Through the BABA-PtrIBIs-PtrVOZ signaling module, poplar plants were able to transduce ABA signaling and regulate their response to drought stress. These results suggest that the PtrIBI genes in poplar have the potential to improve drought tolerance in plants through the topical application of low concentrations of BABA.

The Aux/IAA protein TaIAA15-1A confers drought tolerance in Brachypodium by regulating abscisic acid signal pathway.

KEY MESSAGE: Overexpression of the Aux/IAA protein TaIAA15-1A from wheat improves drought tolerance by regulating the ABA signalling pathway in transgenic Brachypodium. Drought is a major abiotic stress that causes severe crop yield loss. Aux/IAA genes have been shown to be involved in drought stress responses. However, to the best of our knowledge, there has been little research on the molecular mechanism of the wheat Aux/IAA gene in the context of drought tolerance. In this study, we found that expression of the wheat Aux/IAA gene TaIAA15-1A was upregulated by PEG6000, NaCl, SA, JA, IAA and ABA. Transgenic plants overexpressing TaIAA15-1A showed higher drought tolerance than wild-type (WT) plants. The physiological analyses showed that the transgenic lines exhibited a higher survival rate, shoot length, and relative water content than the WT plants. The activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) were enhanced in transgenic lines, causing a reduction in the hydrogen peroxide (H2O2) and superoxide anion radical (O2-) contents. Transcriptome analysis showed that TaIAA15-1A overexpression alters the expression of these genes involved in the auxin signalling pathway, ABA signalling pathway, phenolamides and antioxidant pathways. The results of exogenous ABA treatment suggested that TaIAA15-1A overexpression increased sensitivity to ABA at the germination and postgermination stages compared to WT plants. These results indicate that TaIAA15-1A plays a positive role in plant drought tolerance by regulating ABA-related genes and improving antioxidative stress ability and has potential application in genetically modified crops.

The sweet sorghum SbWRKY50 is negatively involved in salt response by regulating ion homeostasis.

The WRKY transcription factor family is involved in responding to biotic and abiotic stresses. Its members contain a typical WRKY domain and can regulate plant physiological responses by binding to W-boxes in the promoter regions of downstream target genes. We identified the sweet sorghum SbWRKY50 (Sb09g005700) gene, which encodes a typical class II of the WRKY family protein that localizes to the nucleus and has transcriptional activation activity. The expression of SbWRKY50 in sweet sorghum was reduced by salt stress, and its ectopic expression reduced the salt tolerance of Arabidopsis thaliana plants. Compared with the wild type, the germination rate, root length, biomass and potassium ion content of SbWRKY50 over-expression plants decreased significantly under salt-stress conditions, while the hydrogen peroxide, superoxide anion and sodium ion contents increased. Real-time PCR results showed that the expression levels of AtSOS1, AtHKT1 and genes related to osmotic and oxidative stresses in over-expression strains decreased under salt-stress conditions. Luciferase complementation imaging and yeast one-hybrid assays confirmed that SbWRKY50 could directly bind to the upstream promoter of the SOS1 gene in A. thaliana. However, in sweet sorghum, SbWRKY50 could directly bind to the upstream promoters of SOS1 and HKT1. These results suggest that the new WRKY transcription factor SbWRKY50 participates in plant salt response by controlling ion homeostasis. However, the regulatory mechanisms are different in sweet sorghum and Arabidopsis, which may explain their different salt tolerance levels. The data provide information that can be applied to genetically modifying salt tolerance in different crop varieties.

Acoustic source characterization for a logging while drilling tool: Theoretical and experimental modeling.

The development of acoustic source technology has been an important task for acoustic logging while drilling (LWD) and various source designs have been implemented. Using a multipole wave expansion theory, this study demonstrates that a LWD acoustic source can be represented as a combination of monopole, dipole, and quadrupole constituents and characterized by the contribution of each constituent. The theoretical analysis is experimentally demonstrated with a cylindrical pipe simulating the LWD collar. The result of this study can be used to provide a method for evaluating the performance of a LWD acoustic source.

Glycine betaine-mediated potentiation of HSP gene expression involves calcium signaling pathways in tobacco exposed to NaCl stress.

Glycine betaine (GB) can enhance heat tolerance and the accumulation of heat-shock protein (HSP) in plants, but the effects of GB on HSP accumulation during salt stress were not previously known. To investigate the mechanism of how GB influences the expression of HSP, wild-type tobacco (Nicotiana tabacum) seedlings pretreated with exogenous GB and BADH-transgenic tobacco plants that accumulated GB in vivo were studied during NaCl stress. A transient Ca(2+) efflux was observed in the epidermal cells of the elongation zone of tobacco roots after NaCl treatment for 1-2 min. After 24 h of NaCl treatment, an influx of Ca(2+) was observed; a low concentration of GB significantly increased NaCl-induced Ca(2+) influx. GB increased the intracellular free calcium ion concentration and enhanced the expression of the calmodulin (CaM) and heat-shock transcription factor (HSF) genes resulting in potentiated levels of HSPs. Pharmacological experiments confirmed that Ca(2+) and CaM increased HSFs and HSPs gene expression, which coincided with increased the levels of HSP70 accumulation. These results suggest a mechanism by which GB acted as a cofactor in the NaCl induction of a Ca(2+) -permeable current. A possible regulatory model of Ca(2+) -CaM in the signal transduction pathway for induction of transcription and translation of the active HSPs is described.

Functional Characterization of the Soybean Glycine max Actin Depolymerization Factor GmADF13 for Plant Resistance to Drought Stress.

Abiotic stress significantly affects plant growth and has devastating effects on crop production. Drought stress is one of the main abiotic stressors. Actin is a major component of the cytoskeleton, and actin-depolymerizing factors (ADFs) are conserved actin-binding proteins in eukaryotes that play critical roles in plant responses to various stresses. In this study, we found that GmADF13, an ADF gene from the soybean Glycine max, showed drastic upregulation under drought stress. Subcellular localization experiments in tobacco epidermal cells and tobacco protoplasts showed that GmADF13 was localized in the nucleus and cytoplasm. We characterized its biological function in transgenic Arabidopsis and hairy root composite soybean plants. Arabidopsis plants transformed with GmADF13 displayed a more robust drought tolerance than wild-type plants, including having a higher seed germination rate, longer roots, and healthy leaves under drought conditions. Similarly, GmADF13-overexpressing (OE) soybean plants generated via the Agrobacterium rhizogenes-mediated transformation of the hairy roots showed an improved drought tolerance. Leaves from OE plants showed higher relative water, chlorophyll, and proline contents, had a higher antioxidant enzyme activity, and had decreased malondialdehyde, hydrogen peroxide, and superoxide anion levels compared to those of control plants. Furthermore, under drought stress, GmADF13 OE activated the transcription of several drought-stress-related genes, such as GmbZIP1, GmDREB1A, GmDREB2, GmWRKY13, and GmANK114. Thus, GmADF13 is a positive regulator of the drought stress response, and it may play an essential role in plant growth under drought stress conditions. These results provide new insights into the functional elucidation of soybean ADFs. They may be helpful for breeding new soybean cultivars with a strong drought tolerance and further understanding how ADFs help plants adapt to abiotic stress.

The effect of biocontrol bacteria on rhizosphere bacterial communities analyzed by plating and PCR-DGGE.

Bacillus subtilis B579, which was isolated from rhizosphere of cucumber, exhibited an excellent biocontrol activity on soil-born pathogens under greenhouse conditions. It could colonize in rhizosphere of cucumber with large number of populations after inoculated in plant growth season. To reveal the effect of high level colonization of B. subtilis B579 on rhizobacteria community structure, cultivation-based analysis coupled with denaturing gradient gel electrophoresis (DGGE) analysis were used to profile the changes of rhizobacteria community structure sampling at 1 week interval. Cultivation-based and DGGE fingerprinting analysis showed significant plant-dependent and seasonal shifts in rhizobacteria populations. Only minimal and transient effects were observed at 4-9 weeks after sowing in samples of B579 treatment, without the pathogen inoculation and showed the best plant growth potential. Sequencing of dominant bands excised from the gel revealed that Streptomyces sp. was the dominate species in soils before and after sowing. Burkholderia sp. was the dominate species in bulk soil, while Bacillus sp. was dominated in rhizosphere within the growth season. Arthrobacter ramosus and Nocardioides sp. were identified as the specific species in samples treated by B579 at the maturity and flowering stages of cucumber.

Comparative transcriptomic analysis and functional characterization reveals that the class III peroxidase gene TaPRX-2A regulates drought stress tolerance in transgenic wheat.

Drought is a major abiotic stress that reduces crop yields and quality worldwide. Although some genes involved in the response to drought stress have been identified, a more in-depth understanding of the mechanisms underlying wheat tolerance to drought is needed for the control of drought tolerance. Here, we evaluated the drought tolerance of 15 wheat cultivars and measured their physiological-biochemical parameters. Our data showed that the drought tolerance of the resistant wheat cultivars was significantly higher than that of drought-sensitive cultivars, which was associated with a greater antioxidant capacity of the former. Transcriptomic analysis revealed that different mechanisms of drought tolerance exist between the wheat cultivars Ziyou 5 and Liangxing 66. Transcriptomic analysis also revealed a large number of DEGs, including those involved in flavonoid biosynthesis, phytohormone signalling, phenolamides and antioxidants. qRT-PCR was performed, and the results showed that the expression levels of TaPRX-2A were significantly different among the various wheat cultivars under drought stress. Further study revealed that overexpression of TaPRX-2A enhanced tolerance to drought stress through the maintenance of increased antioxidase activities and reductions in ROS contents. Overexpression of TaPRX-2A also increased the expression levels of stress-related genes and ABA-related genes. Taken together, our findings show that flavonoids, phytohormones, phenolamides and antioxidants are involved in the plant response to drought stress and that TaPRX-2A is a positive regulator of this response. Our study provides insights into tolerance mechanisms and highlights the potential of TaPRX-2A overexpression in enhancing drought tolerance in crop improvement programmes.

Genome-wide identification of actin-depolymerizing factor gene family and their expression patterns under various abiotic stresses in soybean (Glycine max).

The actin-depolymerizing factor (ADF) encoded by a family of genes is highly conserved among eukaryotes and plays critical roles in the various processes of plant growth, development, and stress responses via the remodeling of the architecture of the actin cytoskeleton. However, the ADF family and the encoded proteins in soybean (Glycine max) have not yet been systematically investigated. In this study, 18 GmADF genes (GmADF1 - GmADF18) were identified in the soybean genome and were mapped to 14 different chromosomes. Phylogenetic analysis classified them into four groups, which was confirmed by their structure and the distribution of conserved motifs in the encoded proteins. Additionally, 29 paralogous gene pairs were identified in the GmADF family, and analysis of their Ka/Ks ratios indicated their purity-based selection during the evolutionary expansion of the soybean genome. The analysis of the expression profiles based on the RNA-seq and qRT-PCR data indicated that GmADFs were diversely expressed in different organs and tissues, with most of them responding actively to drought- and salt-induced stresses, suggesting the critical roles played by them in various biological processes. Overall, our study shows that GmADF genes may play a crucial role in response to various abiotic stresses in soybean, and the highly inducible candidate genes could be used for further functional studies and molecular breeding in soybean.

Genome-wide evolutionary analysis of AUX/IAA gene family in wheat identifies a novel gene TaIAA15-1A regulating flowering time by interacting with ARF.

Flowering time is a critical agronomic trait that has strong effects on crop yields. Auxin signaling pathway plays an important role in various development processes, such as flowering, grain development. However, no Aux/IAA gene had been reported to have functions involving in wheat flowering time. Here, we systematically performed genome-wide identification, classification, domain distribution, exon-intron structure, chromosome locations and global expression pattern of Aux/IAA gene family in 14 plant genomes (including Triticum aestivum). A phylogenetic model was proposed to infer the Aux/IAA evolutionary history involving in a central exon-intron structure "2121" during evolution. Overexpression of TaIAA15-1A caused an early flowering time in Brachypodium. RNA-seq analysis showed that TaIAA15-1A overexpression alters various pathways including phytohormone signaling pathway, flowering-related pathway, and polyamine biosynthesis pathway. Screening of auxin response factor (ARF) genes identified BdARF16 that interacted with TaIAA15-1A. Exogenous polyamine (spermidine and spermine) treatments promoted early flowering and (putrescine and DCHA) delayed flowering time of WT plants. Our finding will provide insights on mechanisms of Aux/IAAs gene family and TaIAA15-1A, illustrating the potential during crop improvement programs.

Research progress on the roles of actin-depolymerizing factor in plant stress responses.

Actin-depolymerizing factors (ADFs) are highly conserved small-molecule actin-binding proteins found throughout eukaryotic cells. In land plants, ADFs form a small gene family that displays functional redundancy despite variations among its individual members. ADF can bind to actin monomers or polymerized microfilaments and regulate dynamic changes in the cytoskeletal framework through specialized biochemical activities, such as severing, depolymerizing, and bundling. The involvement of ADFs in modulating the microfilaments' dynamic changes has significant implications for various physiological processes, including plant growth, development, and stress response. The current body of research has greatly advanced our comprehension of the involvement of ADFs in the regulation of plant responses to both biotic and abiotic stresses, particularly with respect to the molecular regulatory mechanisms that govern ADF activity during the transmission of stress signals. Stress has the capacity to directly modify the transcription levels of ADF genes, as well as indirectly regulate their expression through transcription factors such as MYB, C-repeat binding factors, ABF, and 14-3-3 proteins. Furthermore, apart from their role in regulating actin dynamics, ADFs possess the ability to modulate the stress response by influencing downstream genes associated with pathogen resistance and abiotic stress response. This paper provides a comprehensive overview of the current advancements in plant ADF gene research and suggests that the identification of plant ADF family genes across a broader spectrum, thorough analysis of ADF gene regulation in stress resistance of plants, and manipulation of ADF genes through genome-editing techniques to enhance plant stress resistance are crucial avenues for future investigation in this field.

Using High-Throughput Phenotyping Analysis to Decipher the Phenotypic Components and Genetic Architecture of Maize Seedling Salt Tolerance.

Soil salinization is a worldwide problem that limits agricultural production. It is important to understand the salt stress tolerance ability of maize seedlings and explore the underlying related genetic resources. In this study, we used a high-throughput phenotyping platform with a 3D laser sensor (Planteye F500) to identify the digital biomass, plant height and normalized vegetation index under normal and saline conditions at multiple time points. The result revealed that a three-leaf period (T3) was identified as the key period for the phenotypic variation in maize seedlings under salt stress. Moreover, we mapped the salt-stress-related SNPs and identified candidate genes in the natural population via a genome-wide association study. A total of 44 candidate genes were annotated, including 26 candidate genes under normal conditions and 18 candidate genes under salt-stressed conditions. This study demonstrates the feasibility of using a high-throughput phenotyping platform to accurately, continuously quantify morphological traits of maize seedlings in different growing environments. And the phenotype and genetic information of this study provided a theoretical basis for the breeding of salt-resistant maize varieties and the study of salt-resistant genes.

The protective mechanisms of CaHSP26 in transgenic tobacco to alleviate photoinhibition of PSII during chilling stress.

A known sweet pepper cDNA clone, CaHSP26 encoding the chloroplast-localized small heat shock protein (CPsHSP), was isolated and introduced into tobacco plants. It has been reported that CaHSP26 is a member of the CPsHSP gene family related to extreme temperature tolerance in plants. In the present work, the transcripts were detected in the transgenic tobacco lines. The actual quantum yield of photosynthesis (ΦPSII), non-photochemical quenching, and stomatal conductance (gs) in the transgenic lines overexpressing CaHSP26 were higher than those in the wild-type plants under a range of photosynthetic photon flux density during chilling stress. Electron microscopic analysis showed that the transgenic line (L1) had larger size of stomata to lessen stomatal limitation. The activities of ascorbate peroxidase (APX), peroxidase (POD) and catalase (CAT) were also higher in the transgenic lines than those in wild-type plants. Additionally, a significant increase in cis-unsaturated fatty acid contents was observed in transgenic lines due to lower temperatures. These results suggested that CaHSP26 protein plays an important role in protection of PSII by maintaining the antioxidative enzyme activities to avoid or mitigate photooxidation and increasing the fluidity of the thylakoid membrane during chilling stress under low irradiance. Key message CaHSP26 protein protects PSII by maintaining the antioxidative enzyme activities to avoid or mitigate photooxidation and increases the fluidity of the thylakoid membrane during chilling stress under low irradiance.

High-Throughput Phenotyping Accelerates the Dissection of the Phenotypic Variation and Genetic Architecture of Shank Vascular Bundles in Maize (Zea mays L.).

The vascular bundle of the shank is an important 'flow' organ for transforming maize biological yield to grain yield, and its microscopic phenotypic characteristics and genetic analysis are of great significance for promoting the breeding of new varieties with high yield and good quality. In this study, shank CT images were obtained using the standard process for stem micro-CT data acquisition at resolutions up to 13.5 µm. Moreover, five categories and 36 phenotypic traits of the shank including related to the cross-section, epidermis zone, periphery zone, inner zone and vascular bundle were analyzed through an automatic CT image process pipeline based on the functional zones. Next, we analyzed the phenotypic variations in vascular bundles at the base of the shank among a group of 202 inbred lines based on comprehensive phenotypic information for two environments. It was found that the number of vascular bundles in the inner zone (IZ_VB_N) and the area of the inner zone (IZ_A) varied the most among the different subgroups. Combined with genome-wide association studies (GWAS), 806 significant single nucleotide polymorphisms (SNPs) were identified, and 1245 unique candidate genes for 30 key traits were detected, including the total area of vascular bundles (VB_A), the total number of vascular bundles (VB_N), the density of the vascular bundles (VB_D), etc. These candidate genes encode proteins involved in lignin, cellulose synthesis, transcription factors, material transportation and plant development. The results presented here will improve the understanding of the phenotypic traits of maize shank and provide an important phenotypic basis for high-throughput identification of vascular bundle functional genes of maize shank and promoting the breeding of new varieties with high yield and good quality.

AtGCS promoter-driven clustered regularly interspaced short palindromic repeats/Cas9 highly efficiently generates homozygous/biallelic mutations in the transformed roots by Agrobacterium rhizogenes-mediated transformation.

Agrobacterium rhizogenes-mediated (ARM) transformation is an efficient and powerful tool to generate transgenic roots to study root-related biology. For loss-of-function studies, transgenic-root-induced indel mutations by CRISPR/Cas9 only with homozygous/biallelic mutagenesis can exhibit mutant phenotype(s) (excluding recessive traits). However, a low frequency of homozygous mutants was produced by a constitutive promoter to drive Cas9 expression. Here, we identified a highly efficient Arabidopsis thaliana gamma-glutamylcysteine synthetase promoter, termed AtGCSpro, with strong activity in the region where the root meristem will initiate and in the whole roots in broad eudicots species. AtGCSpro achieved higher homozygous/biallelic mutation efficiency than the most widely used CaMV 35S promoter in driving Cas9 expression in soybean, Lotus japonicus, and tomato roots. Using the pAtGCSpro-Cas9 system, the average homozygous/biallelic mutation frequency is 1.7-fold and 8.3-fold higher than the p2 × 35Spro-Cas9 system for single and two target site(s) in the genome, respectively. Our results demonstrate the advantage of the pAtGCSpro-Cas9 system used in ARM transformation, especially its great potential in diploids with multiple-copy genes targeted mutations and polyploid plants with multiplex genome editing. AtGCSpro is conservatively active in various eudicots species, suggesting that AtGCSpro might be applied in a wide range of dicots species.

Red Light Regulates the Metabolite Biosynthesis in the Leaves of "Huangjinya" Through Amino Acid and Phenylpropanoid Metabolisms.

"Huangjinya" is a light-sensitive albino variety and is widely cultivated in China. It has been proved that red light could promote the vegetable growth of plants. However, the mechanism of "Huangjinya" in response to a red light is unclear. This study used high-throughput sequencing technology to analyze the transcriptome of tender shoots of "Huangjinya" under the white and red light supplement conditions. At the same time, liquid chromatography tandem mass spectrometry (LC-MS) was used to analyze metabolite changes under different light conditions. Transcriptome analysis revealed that a total of 174 differentially expressed genes (DEGs) were identified after the red light supplement. Kyoto encyclopedia of genes and genomes (KEGG) classification indicated that amino acid metabolism enriched the most DEGs. In addition, two phenylpropanoid metabolism-related genes and five glutathione S-transferase genes (CsGSTs) were found to be expressed differently. Metabolome analysis revealed that 193 differential metabolites were obtained. Being the same as transcriptome analysis, most differential metabolites were enriched in amino acids, sweet and umami tasting amino acids were increased, and bitter-tasting amino acids were decreased after the red light supplement. In summary, red light supplementary treatment may be propitious to the quality of "Huangjinya" due to its regulatory effect on amino acid metabolism. Also, CsGSTs involved phenylpropanoid metabolism contributed to tea quality changes in "Huangjinya."

Synthesis, Fungicidal Activity, and Mechanism of Action of Pyrazole Amide and Ester Derivatives Based on Natural Products l-Serine and Waltherione Alkaloids.

The development of new green fungicides based on the structural optimization of natural products can effectively solve the problems of low safety and high pathogen resistance of traditional fungicides. In this paper, based on pyrazole amide compound h-I-9 with excellent fungicidal activity discovered in the previous work, a series of l-serine-derived pyrazole amide and waltherione alkaloid-derived pyrazole ester derivatives were synthesized. The structures were successively identified by 1H NMR, 13C NMR, high-resolution mass spectrometry, and X-ray single-crystal diffraction. The in vitro and in vivo fungicidal activity screening demonstrated that compound II-5 showed a good inhibition rate against Physalospora piricola. A transmission electron microscope and fluorescence microscope observation further revealed that compound II-5 may cause damage to the cell membranes and vacuoles, and the hyphae treated with II-5 could produce obvious and easily observed blue fluorescence. The succinate dehydrogenase (SDH) enzymatic activity and molecular docking simulation indicated that compounds I-3 and I-4 may be potential SDH inhibitors against Alternaria sp.

Cold-tolerant introgression line construction and low-temperature stress response analysis for bell pepper.

We aimed to screen cold-tolerant introgression lines (ILs) of bell pepper and investigate stress responses of these bell peppers under low temperature. Seedlings of cold-resistant wild-type bell pepper CA157, cultivated bell pepper CA52, and their ILs were evaluated for their tolerance to low temperature. Electrical conductivity measurement was performed on ILs and two parents. Then, contents of physiological and biochemical indexes including malondialdehyde (MDA), proline, and soluble sugar content were examined. Moreover, the superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD) activities were further investigated. Finally, the chlorophyll fluorescence (PSII) parameters in all pant leaves were examined.A total of 22 IL plants showed better resistance than their recurrent parent CA52. CL122 was one of the most outstanding plants in ILs that had similar performance with wild bell pepper CA157. Cold resistance analysis based on physiological and biochemical indexes showed that factors such as electrical conductivity, MDA, and PSII were closely related to cold resistance among CA157, CA52, and CL122 under low-temperature stress. In conclusion, ILs constructed in the current study might be used for cold resistance gene introgression between wild and cultured species. Moreover, CL122 might be a novel bridge material for understanding low-temperature response in bell pepper. Furthermore, electrical conductivity, MDA, and PSII might be used to identify the low-temperature resistance of bell pepper plants in a period of obvious differentiation.

Transcriptome analysis of maize inbred lines differing in drought tolerance provides novel insights into the molecular mechanisms of drought responses in roots.

Maize (Zea mays) is an important food and forage crop, as well as an industrial raw material, that plays important roles in agriculture and national economies. Drought stress has negative effects on seed germination and seedling growth, and it decreases crop production. In this study, we selected two maize inbred lines with different drought-tolerance levels: drought-tolerant 287M and drought-sensitive 753F. The physiological results showed that drought stress resulted in a large accumulation of reactive oxygen species (ROS) in maize root cells. However, in 287M, the activity levels of the ROS scavenging enzymes superoxide dismutase and ascorbate peroxidase also increased, resulting in a higher ROS scavenging ability than 753F. We used Illumina RNA sequencing to obtain the gene expression profiles of the two maize inbred lines at the seedling stage in response to drought stress. The transcriptome data were analyzed to reveal the mechanisms underlying the drought tolerance of 287M at the gene regulatory level. The differences in drought tolerance between 287M and 753F may be associated with different ROS scavenging capabilities, signal interaction networks, and some transcription factors. Our results will aid in understanding the molecular mechanisms involved in plant responses to drought stress.

Constitutive expression of CaHSP22.5 enhances chilling tolerance in transgenic tobacco by promoting the activity of antioxidative enzymes.

Chilling stress limits the productivity and geographical distribution of many organisms throughout the world. In plants, the small heat shock proteins (sHSPs) belong to a group of proteins known as chaperones. The sweet pepper (Capsicum annuum L.) cDNA clone CaHSP22.5, which encodes an endoplasmic reticulum-located sHSP (ER-sHSP), was isolated and introduced into tobacco (Nicotiana tabacum L.) plants and Escherichia coli. The performance index and the maximal efficiency of PSII photochemistry (Fv/Fm) were higher and the accumulation of H2O2 and superoxide radicals (O2-) was lower in the transgenic lines than in the untransformed plants under chilling stress, which suggested that CaHSP22.5 accumulation enhanced photochemical activity and oxidation resistance. However, purified CaHSP22.5 could not directly reduce the contents of H2O2 and O2- in vitro. Additionally, heterologously expressed recombinant CaHSP22.5 enhanced E. coli viability under oxidative stress, helping to elucidate the cellular antioxidant function of CaHSP22.5 in vivo. At the same time, antioxidant enzyme activity was higher, which was consistent with the lower relative electrolyte conductivity and malondialdehyde contents of the transgenic lines compared with the wild-type. Furthermore, constitutive expression of CaHSP22.5 decreased the expression of other endoplasmic reticulum molecular chaperones, which indicated that the constitutive expression of ER-sHSP alleviated endoplasmic reticulum stress caused by chilling stress in plants. We hypothesise that CaHSP22.5 stabilises unfolded proteins as a chaperone and increases the activity of reactive oxygen species-scavenging enzymes to avoid oxidation damage under chilling stress, thereby suggesting that CaHSP22.5 could be useful for improving the tolerance of chilling-sensitive plant types.