Comparative transcriptome analysis to reveal key ethylene genes involved in a Lonicera macranthoides mutant.

BACKGROUND: Lonicera macranthoides Hand.-Mazz. is an important medicinal plant. Xianglei-type (XL) L. macranthoides was formed after many years of cultivation by researchers on the basis of the natural mutant. The corolla of L. macranthoides XL remains unexpanded and its flowering period is nearly three times longer than that of wild-type (WT) plants. However, the molecular mechanism behind this desirable trait remains a mystery. OBJECTIVE: To understand the floral phenotype differences between L. macranthoides and L. macranthoides XL at the molecular level. METHODS: Transcriptome analysis was performed on L. macranthoides XL and WT. One DEG was cloned by RT-PCR amplification and selected for qRT-PCR analysis. RESULTS: Transcriptome analysis showed that there were 5603 differentially expressed genes (DEGs) in XL vs. WT. Enrichment analysis of DEGs showed that pathways related to plant hormone signal transduction were significantly enriched. We identified 23 key genes in ethylene biosynthesis and signal transduction pathways. The most abundant were the ethylene biosynthesis DEGs. In addition, the open reading frames (ORFs) of WT and XL ETR2 were successfully cloned and named LM-ETR2 (GenBank: MW334978) and LM-XL-ETR2 (GenBank: MW334978), respectively. qRT-PCR at different flowering stages suggesting that ETR2 acts in the whole stage of flower development of WT and XL. CONCLUSIONS: This study provides new insight into the molecular mechanism that regulates the development of special traits in the flowers of L. macranthoides XL. The plant hormone ethylene plays an important role in flower development and flowering duration prolongation in L. macranthoides. The ethylene synthesis gene could be more responsible for the flower phenotype of XL. The genes identified here can be used for breeding and improvement of other flowering plants after functional verification.

Combined transcriptome and metabolome analysis of Nerium indicum L. elaborates the key pathways that are activated in response to witches' broom disease.

BACKGROUND: Nerium indicum Mill. is an ornamental plant that is found in parks, riversides, lakesides, and scenic areas in China and other parts of the world. Our recent survey indicated the prevalence of witches' broom disease (WBD) in Guangdong, China. To find out the possible defense strategies against WBD, we performed a MiSeq based ITS sequencing to identify the possible casual organism, then did a de novo transcriptome sequencing and metabolome profiling in the phloem and stem tip of N. indicum plants suffering from WBD compared to healthy ones. RESULTS: The survey showed that Wengyuen county and Zengcheng district had the highest disease incidence rates. The most prevalent microbial species in the diseased tissues was Cophinforma mamane. The transcriptome sequencing resulted in the identification of 191,224 unigenes of which 142,396 could be annotated. There were 19,031 and 13,284 differentially expressed genes (DEGs) between diseased phloem (NOWP) and healthy phloem (NOHP), and diseased stem (NOWS) and healthy stem (NOHS), respectively. The DEGs were enriched in MAPK-signaling (plant), plant-pathogen interaction, plant-hormone signal transduction, phenylpropanoid and flavonoid biosynthesis, linoleic acid and α-linoleic acid metabolism pathways. Particularly, we found that N. indicum plants activated the phytohormone signaling, MAPK-signaling cascade, defense related proteins, and the biosynthesis of phenylpropanoids and flavonoids as defense responses to the pathogenic infection. The metabolome profiling identified 586 metabolites of which 386 and 324 metabolites were differentially accumulated in NOHP vs NOWP and NOHS and NOWS, respectively. The differential accumulation of metabolites related to phytohormone signaling, linoleic acid metabolism, phenylpropanoid and flavonoid biosynthesis, nicotinate and nicotinamide metabolism, and citrate cycle was observed, indicating the role of these pathways in defense responses against the pathogenic infection. CONCLUSION: Our results showed that Guangdong province has a high incidence of WBD in most of the surveyed areas. C. mamane is suspected to be the causing pathogen of WBD in N. indicum. N. indicum initiated the MAPK-signaling cascade and phytohormone signaling, leading to the activation of pathogen-associated molecular patterns and hypersensitive response. Furthermore, N. indicum accumulated high concentrations of phenolic acids, coumarins and lignans, and flavonoids under WBD. These results provide scientific tools for the formulation of control strategies of WBD in N. indicum.

Cross-species transcriptomic analyses reveals common and opposite responses in Arabidopsis, rice and barley following oxidative stress and hormone treatment.

BACKGROUND: For translational genomics, a roadmap is needed to know the molecular similarities or differences between species, such as model species and crop species. This knowledge is invaluable for the selection of target genes and pathways to alter downstream in response to the same stimuli. Here, the transcriptomic responses to six treatments including hormones (abscisic acid - ABA and salicylic acid - SA); treatments that cause oxidative stress (3-amino-1,2,4-triazole - 3AT, methyl viologen - MV); inhibit respiration (antimycin A - AA) or induce genetic damage (ultraviolet radiation -UV) were analysed and compared between Arabidopsis (Arabidopsis thaliana), barley (Hordeum vulgare) and rice (Oryza sativa). RESULTS: Common and opposite responses were identified between species, with the number of differentially expressed genes (DEGs) varying greatly between treatments and species. At least 70% of DEGs overlapped with at least one other treatment within a species, indicating overlapping response networks. Remarkably, 15 to 34% of orthologous DEGs showed opposite responses between species, indicating diversity in responses, despite orthology. Orthologous DEGs with common responses to multiple treatments across the three species were correlated with experimental data showing the functional importance of these genes in biotic/abiotic stress responses. The mitochondrial dysfunction response was revealed to be highly conserved in all three species in terms of responsive genes and regulation via the mitochondrial dysfunction element. CONCLUSIONS: The orthologous DEGs that showed a common response between species indicate conserved transcriptomic responses of these pathways between species. However, many genes, including prominent salt-stress responsive genes, were oppositely responsive in multiple-stresses, highlighting fundamental differences in the responses and regulation of these genes between species. This work provides a resource for translation of knowledge or functions between species.

Modulation of JA signalling reveals the influence of StJAZ1-like on tuber initiation and tuber bulking in potato.

Phytohormones and their interactions play critical roles in Solanum tuberosum (potato) tuberization. The stimulatory role of jasmonic acid (JA) in tuber development is well established because of its significant promotion of tuber initiation and tuber bulking. However, the dynamics and potential function of JA signalling in potato tuberization remain largely unknown. The present study investigated the role of the JAZ1 subtype, a suppressor of JA signalling, in potato tuberization. Using 35S:StJAZ1-like-GUS as a reporter, we showed that JA signalling was attenuated from the bud end to the stem end shortly after tuber initiation. Overexpression of StJAZ1-like suppressed tuber initiation by restricting the competence for tuber formation in stolon tips, as demonstrated by grafting an untransformed potato cultivar to the stock of StJAZ1-like-overexpressing transgenic potato plants (StJAZ1-like ox). In addition, transcriptional profiling analysis revealed that StJAZ1-like modulates the expression of genes associated with transcriptional regulators, cell cycle, cytoskeleton and phytohormones. Furthermore, we showed that StJAZ1-like is destabilised upon treatment with abcisic acid (ABA), and the attenuated tuberization phenotype in StJAZ1-like ox plants can be partially rescued by ABA treatment. Altogether, these results revealed that StJAZ1-like-mediated JA signalling plays an essential role in potato tuberization.

Plant adaptation to low phosphorus availability: Core signaling, crosstalks, and applied implications.

Phosphorus (P) is an essential nutrient for plant growth and reproduction. Plants preferentially absorb P as orthophosphate (Pi), an ion that displays low solubility and that is readily fixed in the soil, making P limitation a condition common to many soils and Pi fertilization an inefficient practice. To cope with Pi limitation, plants have evolved a series of developmental and physiological responses, collectively known as the Pi starvation rescue system (PSR), aimed to improve Pi acquisition and use efficiency (PUE) and protect from Pi-starvation-induced stress. Intensive research has been carried out during the last 20 years to unravel the mechanisms underlying the control of the PSR in plants. Here we review the results of this research effort that have led to the identification and characterization of several core Pi starvation signaling components, including sensors, transcription factors, microRNAs (miRNAs) and miRNA inhibitors, kinases, phosphatases, and components of the proteostasis machinery. We also refer to recent results revealing the existence of intricate signaling interplays between Pi and other nutrients and antagonists, N, Fe, Zn, and As, that have changed the initial single-nutrient-centric view to a more integrated view of nutrient homeostasis. Finally, we discuss advances toward improving PUE and future research priorities.

Integration of transcriptome and targeted metabolome profiling reveals hormone related genes involved in the growth of Bletilla striata.

Bletilla striata (Thunb.) Reichb.f. (BS) is a traditional Chinese medicine with numerous beneficial effects. In our previous study, Aspergillus flavus was isolated from B. striata. To explore the physiological and molecular mechanisms of Aspergillus flavus elicitor (1-G4) that promoted Bletilla striata growth, in this study, we performed the determination of growth indexes and transcriptomics and metabolomics analysis under 5% and 10% 1-G4 conditions. Results showed that 1-G4 elicitor could significantly promote the growth and development of B. striata. With the increasing concentration of 1-G4 elicitor, the contents of SA, ICAld, and ME-IAA significantly increased while the IP and ACC contents decreased dramatically. A total of 1657 DEGs (763 up-regulated and 894 down-regulated) between the control (CK) and 5% elicitor (CK vs G5) and 2415 DEGs (1208 up-regulated and 1207 down-regulated) between the control and 10% elicitor (CK vs G10) were identified. Further, we found that 22, 38, and 2 unigenes were involved in ME-IAA, IP, and ACC, respectively. It was indicated that these unigenes might be involved in B. striata growth. Overall, the current study laid a theoretical foundation for the effective utilization of endophytic fungi and the optimization of germplasm resources of B. striata.

Transcriptomic analysis of Allium sativum uncovers putative genes involved in photoperiodic pathway and hormone signaling under long day and short day conditions.

Photoperiod is dominant environmental factor that controls plant growth and development. Even though research on plants response to photoperiod is significant in agriculture, molecular mechanisms of garlic in response to photoperiod remain largely unknown. In the current investigation, 3 months old garlic plants were treated with long day (LD) and short day (SD) for 10 and 20 days after treatment (DAT). Liquid chromatography-mass spectrometry (LC-MS) analysis of phytohormones exhibited that indole-3-acetic acid (IAA), zeatin riboside (ZR) and salicylic acid (SA) were observed maximum under LD at 10 DAT, whereas abscisic acid (ABA), gibberellic acid 3 (GA3), zeatin (ZT) and jasmonic acid (JA) were observed maximum under LD at 20 DAT. Transcriptome sequencing analysis was done to evaluate the transcriptional response to LD and SD. Differentially expressed genes (DEGs) were detected to have pathway enrichment. i.e., DNA binding transcription factor activity, transcription regulator activity, transferase activity, transferring hexosyl groups, and sequence specific-DNA binding activity, plant hormone signal transduction, circadian rhythm-plant, biosynthesis of amino acids, phenylpropanoid biosynthesis, and starch and sucrose metabolism. Furthermore, 28 and 40 DEGs were identified related to photoperiod and hormone signaling, respectively and their interaction in response to LD and SD were discussed in detail. Outcomes of current investigation might be useful to provide novel resources for garlic bulb formation in response to photoperiod.

The Laccase Gene Family Mediate Multi-Perspective Trade-Offs during Tea Plant (Camellia sinensis) Development and Defense Processes.

Laccase (LAC) plays important roles in different plant development and defense processes. In this study, we identified laccase genes (CsLACs) in Camellia sinensis cv 'Longjing43' cultivars, which were classified into six subclades. The expression patterns of CsLACs displayed significant spatiotemporal variations across different tissues and developmental stages. Most members in subclades II, IV and subclade I exhibited contrasting expression patterns during leaf development, consistent with a trade-off model for preferential expression in the early and late developmental stages. The extensive transcriptional changes of CsLACs under different phytohormone and herbivore treatment were observed and compared, with the expression of most genes in subclades I, II and III being downregulated but genes in subclades IV, V and VI being upregulated, suggesting a growth and defense trade-off model between these subclades. Taken together, our research reveal that CsLACs mediate multi-perspective trade-offs during tea plant development and defense processes and are involved in herbivore resistance in tea plants. More in-depth research of CsLACs upstream regulation and downstream targets mediating herbivore defense should be conducted in the future.

Triacylglycerol biosynthesis in shaded seeds of tung tree (Vernicia fordii) is regulated in part by Homeodomain Leucine Zipper 21.

Light quantity and quality affect many aspects of plant growth and development. However, few reports have addressed the molecular connections between seed oil accumulation and light conditions, especially dense shade. Shade-avoiding plants can redirect plant resources into extension growth at the expense of leaf and root expansion in an attempt to reach areas containing richer light. Here, we report that tung tree seed oil accumulation is suppressed by dense shade during the rapid oil accumulation phase. Transcriptome analysis confirmed that oil accumulation suppression due to dense shade was attributed to reduced expression of fatty acid and triacylglycerol biosynthesis-related genes. Through weighted gene co-expression network analysis, we identified 32 core transcription factors (TFs) specifically upregulated in densely shaded seeds during the rapid oil accumulation period. Among these, VfHB21, a class I homeodomain leucine zipper TF, was shown to suppress expression of FAD2 and FADX, two key genes related to α-eleostearic acid, by directly binding to HD-ZIP I/II motifs in their respective promoter regions. VfHB21 also binds to similar motifs in the promoters of VfWRI1 and VfDGAT2, two additional key seed lipid regulatory/biosynthetic genes. Functional conservation of HB21 during plant evolution was demonstrated by the fact that AtWRI1, AtSAD1, and AtFAD2 were downregulated in VfHB21-overexpressor lines of transgenic Arabidopsis, with concomitant seed oil reduction, and the fact that AtHB21 expression also was induced by shade. This study reveals some of the regulatory mechanisms that specifically control tung tree seed oil biosynthesis and more broadly regulate plant storage carbon partitioning in response to dense shade conditions.

Cytokinin-Based Tissue Cultures for Stable Medicinal Plant Production: Regeneration and Phytochemical Profiling of Salvia bulleyana Shoots.

Salvia bulleyana is a rare Chinese medicinal plant that due to the presence of polyphenols lowers the risk of some chronic diseases especially those related to the cardiovascular system. The present study examines the organogenic competence of various combinations and concentrations of plant growth regulators to develop an efficient protocol for in vitro regeneration of S. bulleyana via leaf explants, maintaining the high production of active constituents. The purpose of the study was also to assess the possibilities of using a cytokinin-based regeneration to effectively produce therapeutic compounds. The adventitious shoot formation was observed through direct organogenesis on media with purine derivatives (meta-topolin, mT and benzylaminopurine, BAP), and through indirect organogenesis on media with urea derivatives (tidiazuron, TDZ and forchlorfenuron, CPPU). The highest regeneration frequency (95%) with 5.2 shoots per explant was obtained on leaves cultured on Murashige and Skoog (MS) medium containing 0.1 mg/L naphthalene-1-acetic acid (NAA) and 2 mg/L BAP. Following inter simple sequence repeat (ISSR) marker-based profiling, the obtained organogenic shoot lines revealed a similar banding pattern to the mother line, with total variability of 4.2-13.7%, indicating high level of genetic stability. The similar genetic profile of the studied lines translated into similar growth parameters. Moreover, HPLC analysis revealed no qualitative differences in the profile of bioactive metabolites; also, the total polyphenol content was similar for different lines, with the exception of the shoots obtained in the presence of CPPU that produced higher level of bioactive compounds. This is the first report of an effective and rapid in vitro organogenesis protocol for S. bulleyana, which can be efficiently employed for obtaining stable cultures rich in bioactive metabolites.

Nanoselenium transformation and inhibition of cadmium accumulation by regulating the lignin biosynthetic pathway and plant hormone signal transduction in pepper plants.

Selenium (Se) can promote the growth and resistance of agricultural crops as fertilizers, while the role of nano-selenium (nano-Se) against Cd remains unclear in pepper plants (Capsicum annuum L.). Biofortification with nano-Se observably restored Cd stress by decreasing the level of Cd in plant tissues and boosting the accumulation in biomass. The Se compounds transformed by nano-Se were primarily in the form of SeMet and MeSeCys in pepper tissues. Differential metabolites and the genes of plant signal transduction and lignin biosynthesis were measured by employing transcriptomics and determining target metabolites. The number of lignin-related genes (PAL, CAD, 4CL, and COMT) and contents of metabolites (sinapyl alcohol, phenylalanine, p-coumaryl alcohol, caffeyl alcohol, and coniferaldehyde) were remarkably enhanced by treatment with Cd1Se0.2, thus, maintaining the integrity of cell walls in the roots. It also enhanced signal transduction by plant hormones and responsive resistance by inducing the biosynthesis of genes (BZR1, LOX3, and NCDE1) and metabolites (brassinolide, abscisic acid, and jasmonic acid) in the roots and leaves. In general, this study can enable a better understanding of the protective mechanism of nano-Se in improving the capacity of plants to resist environmental stress.

Genome-wide identification and expression analysis of the GSK gene family in Solanum tuberosum L. under abiotic stress and phytohormone treatments and functional characterization of StSK21 involvement in salt stress.

Plant Glycogen Synthase Kinase 3 (GSK3)/SHAGGY-like kinase (GSK) proteins play important roles in modulating growth, development, and stress responses in several plant species. However, little is known about the members of the potato GSK (StGSK) family. Here, nine StGSK genes were identified and phylogenetically grouped into four clades. Gene duplication analysis revealed that segmental duplication contributed to the expansion of the StGSK family. Gene structure and motif pattern analyses indicated that similar exon/intron and motif organizations were found in StGSKs from the same clade. Conserved motif and kinase activity analyses indicated that the StGSKs encode active protein kinases, and they were shown to be distributed throughout whole cells. Cis-acting regulatory element analysis revealed the presence of many growth-, hormone-, and stress-responsive elements within the promoter regions of the StGSKs, which is consistent with their expression in different organs, and their altered expression in response to hormone and stress treatments. Association network analysis indicated that various proteins, including two confirmed BES1 family transcription factors, potentially interact with StGSKs. Overexpression of StSK21 provides enhanced sensitivity to salt stress in Arabidopsis thaliana plants. Overall, these results reveal that StGSK proteins are active protein kinases with purported functions in regulating growth, development, and stress responses.

Genome-Wide Identification of the Tify Gene Family and Their Expression Profiles in Response to Biotic and Abiotic Stresses in Tea Plants (Camellia sinensis).

The TIFY family is a plant-specific gene family that is involved in regulating a variety of plant processes, including developmental and defense responses. The chromosome-level genome of the tea plant (Camellia sinensis) has recently been released, but a comprehensive view of the TIFY family in C. sinensis (the CsTIFY genes) is lacking. The current study performed an extensive genome-wide identification of CsTIFY genes. The phylogenetics, chromosome location, exon/intron structure, and conserved domains of these genes were analyzed to characterize the members of the CsTIFY family. The expression profiles of the CsTIFY genes in four organs were analyzed, and they showed different spatial expression patterns. All CsJAZ genes were observed to be induced by jasmonate acid (JA) and exhibited different responses to abiotic and biotic stresses. Six of seven CsJAZ genes (CsJAZ1, CsJAZ2, CsJAZ3, CsJAZ4, CsJAZ7, and CsJAZ8) were upregulated by mechanical wounding and infestation with the tea geometrid (Ectropis obliqua), while infection with tea anthracnose (Colletotrichum camelliae) primarily upregulated the expression levels of CsJAZ1 and CsJAZ10. In addition, CsJAZs were observed to interact with CsMYC2 and AtMYC2. Therefore, the results of this study may contribute to the functional characterization of the CsTIFY genes, especially the members of the JAZ subfamily, as regulators of the JA-mediated defense response in tea plant.

Evidence that ERF transcriptional regulators serve as possible key molecules for natural variation in defense against herbivores in tall goldenrod.

We collected Solidago altissima clones to explore their leaf damage resistance, and as a result identified five accessions that exhibited variable defense abilities against the generalist herbivore Spodoptera litura. In order to characterize molecules involved in such natural variation, we focused on ethylene response factors (ERFs) that exhibited distinct transcription patterns in the leaves of the five accessions (e.g., S1 and S2) after wounding: the transcript of SaERF1 and SaERF2 was induced in wounded S1 and S2 leaves, respectively. Although transcription levels of SaERFs in leaves of the five accessions did not correlate with the accessions' phytohormone levels, these transcription levels accorded with the possibility that ethylene and jasmonate signaling play crucial roles in wound-induced transcription of SaERF1 in S1 leaves, and SaERF2 in S2 leaves, respectively. SaERF1 was found to be a positive regulator of the GCC box and DRE element in the upstream regions of promoters of defense genes, whereas SaERF2 served as a negative regulator of genes controlled through the GCC box. Transgenic Arabidopsis plants expressing SaERF1 or SaERF2 showed enhanced and suppressed transcript levels, respectively, of a defensin gene, indicating that ERFs may be partly responsible for herbivore resistance properties of S. altissima accessions.

AaCOI1, Encoding a CORONATINE INSENSITIVE 1-Like Protein of Artemisia annua L., Is Involved in Development, Defense, and Anthocyanin Synthesis.

Artemisia annua is an important medicinal plant producing the majority of the antimalarial compound artemisinin. Jasmonates are potent inducers of artemisinin accumulation in Artemisisa annua plants. As the receptor of jasmonates, the F-box protein COI1 is critical to the JA signaling required for plant development, defense, and metabolic homeostasis. AaCOI1 from Artemisia annua, homologous to Arabidopsis AtCOI1, encodes a F-box protein located in the nuclei. Expressional profiles of the AaCOI1 in the root, stem, leaves, and inflorescence was investigated. The mRNA abundance of AaCOI1 was the highest in inflorescence, followed by in the leaves. Upon mechanical wounding or MeJA treatment, expression of AaCOI1 was upregulated after 6 h. When ectopically expressed, driven by the native promoter from Arabidopsis thaliana, AaCOI1 could partially complement the JA sensitivity and defense responses, but fully complemented the fertility, and the JA-induced anthocyanin accumulation in a coi1-16 loss-of-function mutant. Our study identifies the paralog of AtCOI1 in Artemisia annua, and revealed its implications in development, hormone signaling, defense, and metabolism. The results provide insight into JA perception in Artemisia annua, and pave the way for novel molecular breeding strategies in the canonical herbs to manipulate the anabolism of pharmaceutic compounds on the phytohormonal level.

Transcriptional trajectories of anther development provide candidates for engineering male fertility in sorghum.

Sorghum is a self-pollinated crop with multiple economic uses as cereal, forage, and biofuel feedstock. Hybrid breeding is a cornerstone for sorghum improvement strategies that currently relies on cytoplasmic male sterile lines. To engineer genic male sterility, it is imperative to examine the genetic components regulating anther/pollen development in sorghum. To this end, we have performed transcriptomic analysis from three temporal stages of developing anthers that correspond to meiotic, microspore and mature pollen stages. A total of 5286 genes were differentially regulated among the three anther stages with 890 of them exhibiting anther-preferential expression. Differentially expressed genes could be clubbed into seven distinct developmental trajectories using K-means clustering. Pathway mapping revealed that genes involved in cell cycle, DNA repair, regulation of transcription, brassinosteroid and auxin biosynthesis/signalling exhibit peak expression in meiotic anthers, while those regulating abiotic stress, carbohydrate metabolism, and transport were enriched in microspore stage. Conversely, genes associated with protein degradation, post-translational modifications, cell wall biosynthesis/modifications, abscisic acid, ethylene, cytokinin and jasmonic acid biosynthesis/signalling were highly expressed in mature pollen stage. High concurrence in transcriptional dynamics and cis-regulatory elements of differentially expressed genes in rice and sorghum confirmed conserved developmental pathways regulating anther development across species. Comprehensive literature survey in conjunction with orthology analysis and anther-preferential accumulation enabled shortlisting of 21 prospective candidates for in-depth characterization and engineering male fertility in sorghum.

Investigation of the genes associated with a male sterility mutant (msm) in Chinese cabbage (Brassica campestris ssp. pekinensis) using RNA-Seq.

In Chinese cabbage, hybrid seed production is performed using male sterility lines, an important approach to heterosis utilization. In this study, a stably inherited male sterile mutant msm was obtained from the 'FT'-doubled haploid line of Chinese cabbage using isolated microspore culture combined with 60Co γ-ray mutagenesis. The genetic backgrounds of 'FT' and msm were highly consistent; however, compared with wild-type 'FT', msm exhibited completely degenerated stamens and no pollen phenotype. Other characters showed no significant differences. Cytological observations revealed that stamen abortion in msm begins during the tetrad period and that tapetum cells were abnormally expanded and highly vacuolated, leading to microspore abortion. Genetic analysis indicated that the msm mutant phenotype is controlled by a single recessive nuclear gene. Comparative transcriptome analysis of 'FT' and msm flower buds using RNA-Seq technology revealed 1653 differentially expressed genes, among which, a large number associated with male sterility were detected, including 64 pollen development- and pollen tube growth-related genes, 94 pollen wall development-related genes, 11 phytohormone-related genes, and 16 transcription factor-related genes. An overwhelming majority of these genes were down-regulated in msm compared with 'FT'. Furthermore, KEGG pathway analysis indicated that a variety of carbohydrate metabolic and lipid metabolic pathways were significantly enriched, which may be related to pollen abortion. The expression patterns of 24 male sterility-related genes were analyzed using qRT-PCR. In addition, 24,476 single-nucleotide polymorphisms and 413,073 insertion-deletion events were specifically detected in msm. These results will facilitate elucidation of the regulatory mechanisms underlying male sterility in Chinese cabbage.

Characterization and functional analysis of two novel 3-hydroxy-3-methylglutaryl-coenzyme A reductase genes (GbHMGR2 and GbHMGR3) from Ginkgo biloba.

Terpene trilactones (TTLs) are the main secondary metabolites of Ginkgo biloba. As one of the rate-limiting enzymes in the mevalonic acid (MVA) pathway of TTL biosynthesis, 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR) catalyzes the 3-hydroxy-3-methylglutaryl coenzyme A to form MVA. In this study, two cDNA sequences of HMGR genes, namely, GbHMGR2 and GbHMGR3, were cloned from G. biloba. The protein sequences of GbHMGR2 and GbHMGR3, which contain several functional domains, were analyzed. Regulatory elements related to light, hormone, and stress response were detected in the promoter regions of GbHMGR2 and GbHMGR3. The catalytic activity of these genes was verified by a functional complement experiment in yeast. Quantitative real-time PCR (qRT-PCR) showed the distinct expression patterns of the two genes in different organs. The TTL contents in the organs were detected by high-performance liquid chromatography- evaporative light scattering detector. GbHMGR2 and GbHMGR3 were responded to cold, dark, methyl jasmonate (MJ), abscisic acid (ABA), salicylic acid (SA), and ethephon (Eth) treatments. The TTL contents were also regulated by cold, dark, MJ, ABA, SA, and Eth treatment. In conclusion, GbHMGR2 and GbHMGR3 may participate in the MVA pathway of TTL biosynthesis.

Identification and Analysis of Genes Involved in Auxin, Abscisic Acid, Gibberellin, and Brassinosteroid Metabolisms Under Drought Stress in Tender Shoots of Tea Plants.

Endogenous phytohormones auxin (indole-3-acetic acid [IAA]), abscisic acid (ABA), gibberellin (GA3), and brassinosteroid (BR) play a role in responses to drought stress in higher plants. Tea plant is one of the major economic corps worldwide. The tender shoots of tea plants are the main source for tea production. The effects of drought stress on endogenous IAA, ABA, GA3, and BR metabolisms in tender shoots of tea plants need to be illustrated. In this study, a total of 17 IAA-related genes, 17 ABA-related genes, 18 GA3-related genes, and 8 BR-related genes were identified under drought stress in tender shoots of tea plants, respectively. By using a combination of phytohormone determination, phylogenetic tree construction and sequence analysis, gene expression profiles, functional classification, Kyoto encyclopedia of genes and genomes enrichment, and distribution of genes analysis, we have demonstrated that IAA, ABA, GA3, and BR metabolisms might participate in the regulation of the response to drought stress in tender shoots of tea plants. The expression level of CsLYCE negatively correlated with ABA accumulation under drought stress. Our findings could shed new light on the effects of drought stress on the IAA, ABA, GA3, and BR metabolisms in tender shoots of tea plants.

Virulence mechanisms of plant-pathogenic Streptomyces species: an updated review.

Gram-positive Actinobacteria from the genus Streptomyces are best known for their morphological complexity and for their ability to produce numerous bioactive specialized metabolites with useful applications in human and veterinary medicine and in agriculture. In contrast, the ability to infect living plant tissues and to cause diseases of root and tuber crops such as potato common scab (CS) is a rare attribute among members of this genus. Research on the virulence mechanisms of plant-pathogenic Streptomyces spp. has revealed the importance of the thaxtomin phytotoxins as key pathogenicity determinants produced by several species. In addition, other phytotoxic specialized metabolites may contribute to the development or severity of disease caused by Streptomyces spp., along with the production of phytohormones and secreted proteins. A thorough understanding of the molecular mechanisms of plant pathogenicity will enable the development of better management procedures for controlling CS and other plant diseases caused by the Streptomyces.