Multiple Functions of MYB Transcription Factors in Abiotic Stress Responses

SmWRKY11 acts as a positive regulator in eggplant response to salt stress

Salt stress is one of the most threatening abiotic stresses to plants, which can seriously affect plant growth, development, reproduction, and yield. However, the mechanisms of plant against salt stress largely remain unclear. Herein, SmWRKY11, an assumed WRKY transcription factor, was functionally characterized in eggplant against salt stress. SmWRKY11 was significantly up-regulated by salt, dehydration stress, and ABA treatment. SmWRKY11 located in the nucleus, and the Plant_zn_clust conserved domain exhibited transcriptional activation activity. Silencing of SmWRKY11 enhanced the susceptibility of eggplant to salt stress, accompanied by significantly down-regulation of transcript expression levels of salt stress defense-related genes SmNCED1, SmGSTU10, and positive regulator of salt stress response SmERF1 as well as increase of hydrogen peroxide (H2O2) content and decrease of the enzyme activities of catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX). In addition, silencing of SmERF1 also could significantly down-regulate SmWRKY11 expression in eggplant response to salt stress. By luciferase reporter assay and chromatin immunoprecipitation PCR assay, SmERF1 expression was found to be indirectly activated by SmWRKY11. These data indicate that SmWRKY11 acts as a positive regulator by forming positive feedback loop with SmERF1 via an indirect regulatory manner in eggplant response to salt stress.

Metabolome and transcriptome analyses provide new insights into the mechanisms underlying the enhancement of medicinal component content in the roots of Acanthopanax senticosus (Rupr. et Maxim.) Harms through foliar application of zinc fertilizer

Acanthopanax senticosus (Rupr. et Maxim.) Harms is a perennial shrub of the Acanthopanax genus in the Araliaceae family and has a high medicinal value. The application of zinc fertilizer can improve the yield and quality of medicinal materials. However, there are limited reports on approaches to increase the content of medicinal components in A. senticosus, hindering the improvement of its medicinal quality. In this study, A. senticosus was treated with 0.1% (LZn) and 0.4% (HZn) zinc sprayed on the leaf surface. The effects of zinc treatment on the medicinal components in the roots of A. senticosus were analyzed by comprehensive metabolomics and transcriptomics analyses. A total of 316 metabolites were detected, with a prevailing occurrence of terpenoids and phenylpropanoids. We identified metabolites related to the medicinal components that were upregulated after Zn treatment, including 43 terpenoids, 19 phenylpropanoids, eight phenols, and three flavonoids. Combining differential gene expression and K-means analysis, we found 95, 65, and 25 upregulated genes related to phenylpropanoid biosynthesis, terpenoid biosynthesis, and flavonoid biosynthesis, respectively. Under different concentrations of Zn treatment, the upregulated metabolite biosynthesis-related genes and differentially expressed transcription factors varied. Pearson correlation network analysis revealed significant correlations among terpenoids, phenylpropanoids, flavonoids biosynthetic genes, and several transcription factors (ERFs, WRKYs, bHLHs, NACs, and MYBs). This study lays the foundation for understanding the metabolic processes in response to varying levels of zinc foliar spray and provides a theoretical basis for enhancing the efficiency of zinc fertilizer utilization in A. senticosus.

Construction of heat stress regulation networks based on Illumina and SMRT sequencing data in potato

Potato (Solanum tuberosum L.) is one of the most important tuber food crops in the world; however, the cultivated potatoes are susceptible to high temperature, by which potato production is adversely affected. Understanding the coping mechanism of potato to heat stress is essential to secure yield and expand adaptability under environmental conditions with rising temperature. However, the lack of heat-related information has significantly limited the identification and application of core genes. To gain deeper insights into heat tolerance genes, next-generation sequencing and single-molecule real-time sequencing were used to learn the transcriptional response of potato to heat stress and 13,159 differentially expressed genes (DEGs) were identified in this study. All DEGs were grouped into 12 clusters using the K-means clustering algorithm. Gene Ontology enrichment analysis revealed that they were involved in temperature signaling, phytohormone, and protein modification. Among them, there were 950 differentially expressed transcription factors (DETFs). According to the network analysis of DETFs at the sixth hour under heat stress, we found some genes that were previously reported to be associated with photoperiodic tuberization, StCO (CONSTANS), tuber formation, StBEL11 (BEL1-LIKE 11), and earliness in potato, StCDF1 (CYCLING DOF FACTOR 1) responding to temperature. Furthermore, we verified the relative expression levels using quantitative real-time polymerase chain reaction, and the results were consistent with the inferences from transcriptomes. In addition, there were 22,125 alternative splicing events and 2,048 long non-coding RNAs. The database and network established in this study will extend our understanding of potato response to heat stress. It ultimately provided valuable resources for molecular analysis of heat stress response in potato and cultivation of potato varieties with heat tolerance.

Review on nitric oxide at the forefront of rapid systemic signaling in mitigation of salinity stress in plants: Crosstalk with calcium and hydrogen peroxide

Soil salinity is a global issue that limits plant growth in agricultural fields and contributes to food crisis. Salt stressors impede plant's ionic, osmotic, and oxidative balance, as well as a variety of physiological functions. Exposure to salinity stress manifest considerable ROS clustering, entailing modification in performance of various organelles. To deal with salinity, plants use a variety of coping strategies, such as osmoregulation, ion-homeostasis, increased antioxidant synthesis, and so on. Nitric oxide (NO) is a pivotal signalling molecule that helps facilitate salt stress-induced physiological plant responses. A variety of evidences point to NO being produced under similar stress conditions and with similar kinetics as hydrogen peroxide (H2O2). The interplay between H2O2 and NO has important functional implications for modulating plant transduction processes. Besides, NO and calcium (Ca2+)-dependent pathways also have some connection in salt stress response mechanisms. Extensive crosstalk between NO and Ca2+ signalling pathways is investigated, and it suggests that almost every type of Ca2+ channel is under the tight control of NO, and NO acts as a Ca2+ mobilising compound and aids in signal reliance. The review provides insights into understanding recent advances regarding NO's, Ca2+ and H2O2 role in salt stress reduction with entwine signaling mechanisms.

Integration of multi-omics analyses highlights the secondary metabolism response of tomato fruit to low temperature storage

Inappropriate low temperature storage usually leads to quality deterioration of harvested tomato fruits. In this study, we performed comparative metabolome, transcriptome, and proteome analyses to comprehensively understand the effects of low temperature on metabolic changes in tomato fruit (fresh fruit, C0d; 4 °C 8 days, C8d; 4 °C 7 days and then 25 °C 1 day, C7dS1). Large amounts of secondary metabolites (including flavonoids and phenolic acids) increased after low temperature treatment. The overlap differentially accumulated metabolites in three comparative groups (C0d vs. C8d, C0d vs. C7dS1, C8d vs. C7dS1) were mainly flavonoid metabolites. A total of 1438 differentially expressed genes identified in these three comparative groups were primarily enriched in metabolic pathways and secondary metabolites biosynthesis pathways. Similarly, proteomic analysis showed that the differentially expressed proteins were enriched in the secondary metabolites biosynthesis and phenylpropanoid biosynthesis pathways. There was a strong correlation between changes in flavonoid metabolites and the expression of chalcone synthase (SlCHS), chalcone isomerase-like (SlCHIL), and coumarate 3-hydroxylase (SlC3H), which are involved in the phenylpropanoid and flavonoid biosynthesis. Additionally, seven differentially expressed MYB transcription factors were identified; SlMYB91, SlMYB106, and SlMYB70 strongly correlated with flavonoid biosynthesis structural genes after low temperature treatment. Other genes involved in fruit ripening and quality were also affected by low temperature. The data generated in this study may unravel the transcriptional regulatory network of secondary metabolism associated with low-temperature storage and provide a solid foundation for future studies.

Mutation of MYB36 affects isoflavonoid metabolism, growth, and stress responses in Lotus japonicus

Isoflavonoids are mostly produced by legumes although little is known about why and how legumes are able to regulate the biosynthesis of these particular compounds. Understanding the role of potential regulatory genes of the isoflavonoid biosynthetic pathway constitutes an important topic of research. The LORE1 mutation of the gene encoding the transcription factor MYB36 allowed the identification of this gene as a regulator of isoflavonoid biosynthesis in Lotus japonicus plants. The levels of several isoflavonoid compounds were considerably lower in two lines of Ljmyb36 mutant plants compared to the WT. In addition, we found that Ljmyb36 mutant plants were significantly smaller and showed a substantial decrease in the chlorophyll levels under normal growth conditions. The analysis of plants subjected to different types of abiotic stress conditions further revealed that mutant plants presented a higher sensitivity than WT plants, indicating that the MYB36 transcription factor is also involved in the stress response in L. japonicus plants.

PagMYB205 Negatively Affects Poplar Salt Tolerance through Reactive Oxygen Species Scavenging and Root Vitality Modulation

Salt stress is one of the major abiotic stresses that limits plant growth and development. The MYB transcription factor family plays essential roles in plant growth and development, as well as stress tolerance processes. In this study, the cDNA of the 84K poplar (Populus abla × Populus glandulosa) was used as a template to clone the full length of the PagMYB205 gene fragment, and transgenic poplar lines with PagMYB205 overexpression (OX) or inhibited expression (RNAi, RNA interference) were cultivated. The role of PagMYB205 in poplar growth and development and salt tolerance was detected using morphological and physiological methods. The full-length CDS sequence of PagMYB205 was 906 bp, encoding 301 amino acids, and the upstream promoter sequence contained abiotic stress-related cis-acting elements. The results of subcellular localization and transactivation assays showed that the protein had no self-activating activity and was localized in the nucleus. Under salt stress, the rooting rate and root vitality of RNAi were higher than OX and wild type (WT). However, the malondialdehyde (MDA) content of the RNAi lines was significantly lower than that of the wild-type (WT) and OX lines, but the reactive oxygen species (ROS) scavenging ability, such as the peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) enzyme activities, was dramatically more powerful. Most significantly of all, the RNAi3 line with the lowest expression level of PagMYB205 had the lowest MDA content, the best enzyme activity and root vitality, and the best salt stress tolerance compared to the other lines. The above results suggest that the transcription factor PagMYB205 could negatively regulate salt stress tolerance by regulating antioxidant enzyme activity and root vitality.

Identification of quantitative trait loci for drought tolerance in Bukoba/Kijivu Andean mapping population of common bean

KEY MESSAGE

Quantitative Trait Loci "hotspots" for drought tolerance were identified on chromosomes Pv06, Pv07 and Pv10 of common bean. Drought is a major production constraint of common bean (Phaseolus vulgaris L.) worldwide. The objective of this study was to identify the Quantitative Trait Loci (QTL) for drought tolerance in an Andean population of Recombinant Inbred Lines (RILs). A total of 155 F5:7 RILs derived from a cross between Kijivu (drought tolerant) and Bukoba (drought susceptible) were evaluated for drought tolerance in field and pot experiments. Four field experiments were conducted at three locations in Zambia in 2020 and 2021. All field trials were conducted in the dry season under irrigation. The 155 RILs were genotyped with 11,292 SNPs, and composite interval mapping was conducted to identify QTL for drought tolerance. Seed yield for Kijivu under drought stress was consistently higher than for Bukoba across all four field trials. A total of 60 QTL were identified for morphological, agronomic, and physiological traits under drought stress and non-stress conditions. However, the majority of these QTL were specific to drought stress. QTL "hotspots" for drought tolerance were identified on chromosomes Pv06, Pv07, and Pv10. Extensive co-localizations for agronomic and morpho-physiological traits under drought stress were observed at the three drought-tolerance QTL hotspots. Additionally, these three QTL hotspots overlapped with previously identified QTL for drought tolerance, while several others identified QTL are novel. The three identified QTL hotspots could be used in future marker-assisted selection for drought tolerance in common bean.

Genome-wide identification of GH9 gene family and the assessment of its role during fruit abscission zone formation in Vaccinium ashei

KEY MESSAGE

The genomic location and stage-specific expression pattern of GH9 genes reveal their critical roles during fruit abscission zone formation in Vaccinium ashei. Glycosyl hydrolase family 9 (GH9) cellulases play a crucial role in both cellulose synthesis and hydrolysis during plant growth and development. Despite this importance, there is currently no study on the involvement of GH9-encoding genes, specifically VaGH9s, in abscission zone formation of rabbiteye blueberries (Vaccinium ashei). In this study, we identified a total of 61 VaGH9s in the genome, which can be classified into 3 subclasses based on conserved motifs and domains, gene structures, and phylogenetic analyses. Our synteny analysis revealed that VaGH9s are more closely related to the GH9s of Populus L. than to those of Arabidopsis, Vitis vinifera, and Citrus sinensis. In silico structural analysis predicted that most of VaGH9s are hydrophilic, and localized in cell membrane and/or cell wall, and the variable sets of cis-acting regulatory elements and functional diversity with four categories of stress response, hormone regulation, growth and development, and transcription factor-related elements are present in the promoter sequence of VaGH9s genes. Transcriptomic analysis showed that there were 22 differentially expressed VaGH9s in fruit abscission zone tissue at the veraison stage, and the expression of VaGH9B2 and VaGH9C10 was continuously increased during fruit maturation, which were in parallel with the increasing levels of cellulase activity and oxidative stress indicators, suggesting that they are involved in the separation stage of fruit abscission in Vaccinium ashei. Our work identified 22 VaGH9s potentially involved in different stages of fruit abscission and would aid further investigation into the molecular regulation of abscission in rabbiteye blueberries fruit.

Genome-wide identification of the longan R2R3-MYB gene family and its role in primary and lateral root

R2R3-MYB is an important transcription factor family that regulates plant growth and development. Root development directly affects the absorption of water and nutrients by plants. Therefore, to understand the regulatory role of R2R3-MYB transcription factor family in root development of longan, this study identified the R2R3-MYB gene family members at the genome-wide level, and analyzed their phylogenetic characteristics, physical and chemical properties, gene structure, chromosome location and tissue expression. The analysis identified 124 R2R3-MYB family members in the longan genome. Phylogenetic analysis divided these members into 22 subfamilies, and the members of the unified subfamily had similar motifs and gene structures. The result of qRT-PCR showed that expression levels of DlMYB33, DlMYB34, DlMYB59, and DlMYB77 were significantly higher in main roots than in lateral as opposed to those of DlMYB35, DlMYB69, DlMYB70, and DlMYB83, which were significantly lower. SapBase database prediction and miRNAs sequencing results showed that 34 longan miRNAs could cleave R2R3-MYB, including 17 novel miRNAs unique to longan. The qRT-PCR and subcellular localization experiments of DlMYB92 and DlMYB98 showed that DlMYB92 is a key factor that regulates transcription in the nucleus and participates in the regulation of longan lateral root development. Longan also has a conserved miRNA-MYB-lateral root development regulation mechanism. This study provides a reference for further research on the transcriptional regulation of the miRNA-R2R3-MYB module in the root development of longan.

Metabolite profiling and transcriptomic analyses demonstrate the effects of biocontrol agents on alkaloid accumulation in Fritillaria thunbergii

BACKGROUND

During Fritillaria thunbergii planting, pests and diseases usually invade the plant, resulting in reduced yield and quality. Previous studies have demonstrated that using biocontrol agents can effectively control grubs and affect the steroid alkaloids content in F. thunbergii. However, the molecular regulatory mechanisms underlying the differences in the accumulation of steroid alkaloids in response to biocontrol agents remain unclear.

RESULTS

Combined transcriptomic and metabolic analyses were performed by treating the bulbs of F. thunbergii treated with biocontrol agents during planting. Otherwise, 48 alkaloids including 32 steroid alkaloids, 6 indole alkaloids, 2 scopolamine-type alkaloids, 1 isoquinoline alkaloid, 1 furoquinoline alkaloid, and 6 other alkaloids were identified. The content of steroidal alkaloids particularly peimine, peiminine, and veratramine, increased significantly in the group treated with the biocontrol agents. Transcriptome sequencing identified 929 differential genes using biocontrol agents, including 589 upregulated and 340 downregulated genes. Putative biosynthesis networks of steroid alkaloids have been established and combined with differentially expressed structural unigenes, such as acetyl-CoA C-acetyl-transferase, acelyl-CoAC-acetyltransferase3-hydroxy-3-methylglutaryl-coenzyme A synthase, 1-deoxy-D-xylulose-5-phosphate reductor-isomerase, 2-C-methyl-D-erythritol-4-phosphate cytidylyltransferase and 4-hydroxy-3-methylbut-2-enyl diphosphate reductase. In addition, biological processes such as amino acid accumulation and oxidative phosphorylation were predicted to be related to the synthesis of steroid alkaloids. Cytochrome P450 enzymes also play crucial roles in the steroid alkaloid synthesis. The transcription factor families MYB and bHLH were significantly upregulated after using biocontrol agents.

CONCLUSIONS

Biocontrol agents increased the steroid alkaloids accumulation of steroid alkaloids by affecting key enzymes in the steroid alkaloid synthesis pathway, biological processes of oxidative phosphorylation and amino acid synthesis, cytochrome P450 enzymes, and transcription factors. This study revealed the mechanism underlying the difference in steroidal alkaloids in F. thunbergii after using biocontrol agents, laying the groundwork for future industrial production of steroid alkaloids and ecological planting of medicinal materials in the future.

Analysis of the response mechanisms of Pinellia ternata to terahertz wave stresses using transcriptome and metabolic data

Pinellia ternata (Thunb.) Breit. (Araceae), a significant medicinal plant, has been used to treat various diseases for centuries. Terahertz radiation (THZ) is located between microwaves and infrared rays on the electromagnetic spectrum. THZ possesses low single-photon energy and a spectral fingerprint, but its effects on plant growth have not yet been investigated. The study's primary objective was to examine the transcriptome and metabolome databases of the SY line to provide a new perspective for identifying genes associated with resistance and growth promotion and comprehending the underlying molecular mechanism. Variations in the biological characteristics of P. ternata grown under control and experimental conditions were analyzed to determine the effect of THZ. Compared with the control group, phenotypic variables such as leaf length, petiole length, number of leaves, leaf petiole diameter, and proliferation coefficient exhibited significant differences. P. ternata response to THZ was analyzed regarding the effects of various coercions on root exudation. The experimental group contained considerably more sugar alcohol than the control group. The transcriptome analysis revealed 1,695 differentially expressed genes (DEGs), including 509 upregulated and 1,186 downregulated genes. In the KEGG-enriched plant hormone signaling pathway, there were 19 differentially expressed genes, 13 of which were downregulated and six of which were upregulated. In the metabolomic analysis, approximately 416 metabolites were uncovered. There were 112 DEMs that were downregulated, whereas 148 were upregulated. The P. ternata leaves displayed significant differences in phytohormone metabolites, specifically in brassinolide (BR) and abscisic acid (ABA). The rise in BR triggers alterations in internal plant hormones, resulting in faster growth and development of P. ternata. Our findings demonstrated a link between THZ and several metabolic pathway processes, which will enhance our understanding of P. ternata mechanisms.

Integration of miRNA dynamics and drought tolerant QTLs in rice reveals the role of miR2919 in drought stress response

To combat drought stress in rice, a major threat to global food security, three major quantitative trait loci for 'yield under drought stress' (qDTYs) were successfully exploited in the last decade. However, their molecular basis still remains unknown. To understand the role of secondary regulation by miRNA in drought stress response and their relation, if any, with the three qDTYs, the miRNA dynamics under drought stress was studied at booting stage in two drought tolerant (Sahbaghi Dhan and Vandana) and one drought sensitive (IR 20) cultivars. In total, 53 known and 40 novel differentially expressed (DE) miRNAs were identified. The primary drought responsive miRNAs were Osa-MIR2919, Osa-MIR3979, Osa-MIR159f, Osa-MIR156k, Osa-MIR528, Osa-MIR530, Osa-MIR2091, Osa-MIR531a, Osa-MIR531b as well as three novel ones. Sixty-one target genes that corresponded to 11 known and 4 novel DE miRNAs were found to be co-localized with the three qDTYs, out of the 1746 target genes identified. We could validate miRNA-mRNA expression under drought for nine known and three novel miRNAs in eight different rice genotypes showing varying degree of tolerance. From our study, Osa-MIR2919, Osa-MIR3979, Osa-MIR528, Osa-MIR2091-5p and Chr01_11911S14Astr and their target genes LOC_Os01g72000, LOC_Os01g66890, LOC_Os01g57990, LOC_Os01g56780, LOC_Os01g72834, LOC_Os01g61880 and LOC_Os01g72780 were identified as the most promising candidates for drought tolerance at booting stage. Of these, Osa-MIR2919 with 19 target genes in the qDTYs is being reported for the first time. It acts as a negative regulator of drought stress tolerance by modulating the cytokinin and brassinosteroid signalling pathway.

Insight into gene expression associated with DNA methylation and small RNA in the rhizome-root system of Moso bamboo

Moso bamboo (Phyllostachys edulis), typically a monopodial scattering bamboo, is famous for its rapid growth. The rhizome-root system of Moso bamboo plays a crucial role in its clonal growth and spatial distribution. However, few studies have focused on rhizome-root systems. Here we collected LBs, RTs, and RGFNSs, the most important parts of the rhizome-root system, to study the molecular basis of the rapid growth of Moso bamboo due to epigenetic changes, such as DNA modifications and small RNAs. The angle of the shoot apical meristem of LB gradually decreased with increasing distance from the mother plant, and the methylation levels of LB were much higher than those of RT and RGFNS. 24 nt small RNAs and mCHH exhibited similar distribution patterns in transposable elements, suggesting a potential association between these components. The miRNA abundance of LB gradually increased with increasing distance from the mother plant, and a negative correlation was observed between gene expression levels and mCG and mCHG levels in the gene body. This study paves the way for further exploring the effects of epigenetic factors on the physiology of Moso bamboo.

Co-expression network analysis of diverse wheat landraces reveals markers of early thermotolerance and a candidate master regulator of thermotolerance genes

Triticum aestivum L. (bread wheat) is a crop relied upon by billions of people around the world, as a major source of both income and calories. Rising global temperatures, however, pose a genuine threat to the livelihood of these people, as wheat growth and yields are extremely vulnerable to damage by heat stress. Here we present the YoGI wheat landrace panel, comprising 342 accessions that show remarkable phenotypic and genetic diversity thanks to their adaptation to different climates. We quantified the abundance of 110 790 transcripts from the panel and used these data to conduct weighted co-expression network analysis and to identify hub genes in modules associated with abiotic stress tolerance. We found that the expression of three hub genes, all heat-shock proteins (HSPs), were significantly correlated with early thermotolerance in a validation panel of landraces. These hub genes belong to the same module, with one (TraesCS4D01G207500.1) being a candidate master-regulator potentially controlling the expression of the other two hub genes, as well as a suite of other HSPs and heat-stress transcription factors (HSFs). In this work, therefore, we identify three validated hub genes, the expression of which can serve as markers of thermotolerance during early development, and suggest that TraesCS4D01G207500.1 is a potential master regulator of HSP and HSF expression - presenting the YoGI landrace panel as an invaluable tool for breeders wishing to determine and introduce novel alleles into modern varieties, for the production of climate-resilient crops.

Genome-wide association study of drought tolerance traits in sugar beet germplasms at the seedling stage

Introduction: Sugar beets are an important crop for global sugar production. Intense drought and the increasing lack of water resources pose a great threat to sugar beet cultivation. It is a priority to investigate favourable germplasms and functional genes to improve the breeding of drought tolerant plants. Methods: Thus, in this study, 328 sugar beet germplasms were used in a genome-wide association study (GWAS) to identify single nucleotide polymorphism (SNP) markers and candidate genes associated with drought tolerance. Results: The results showed that under drought stress (9% PEG-6000), there were 11 significantly associated loci on chromosomes 2, 3, 5, 7, and 9 from the 108946 SNPs filtered using a mixed linear model (MLM). Genome-wide association analysis combined with qRT-PCR identified 13 genes that were significantly differentially expressed in drought-tolerant extreme materials. Discussion: These candidate genes mainly exhibited functions such as regulating sugar metabolism, maintaining internal environmental stability and participating in photosystem repair. This study provides valuable information for exploring the molecular mechanisms of drought tolerance and improvement in sugar beet.

Overexpression of TaMYB4 Confers Freezing Tolerance in Arabidopsis thaliana

Freezing stress is one of the main factors limiting the growth and yield of wheat. In this study, we found that TaMYB4 expression was significantly upregulated in the tillering nodes of the strong cold-resistant winter wheat variety Dongnongdongmai1 (Dn1) under freezing stress. Weighted gene co-expression network analysis, qRT-PCR and protein-DNA interaction experiments demonstrated that monodehydroascorbate reductase (TaMDHAR) is a direct target of TaMYB4. The results showed that overexpression of TaMYB4 enhanced the freezing tolerance of transgenic Arabidopsis. In TaMYB4 overexpression lines (OE-TaMYB4), AtMDHAR2 expression was upregulated and ascorbate-glutathione (AsA-GSH) cycle operation was enhanced. In addition, the expression of cold stress marker genes such as AtCBF1, AtCBF2, AtCBF3, AtCOR15A, AtCOR47, AtKIN1 and AtRD29A in OE-TaMYB4 lines was significantly upregulated. Therefore, TaMYB4 may increase freezing tolerance as a transcription factor (TF) in Arabidopsis through the AsA-GSH cycle and DREB/CBF signaling pathway. This study provides a potential gene for molecular breeding against freezing stress.

The RNA-binding protein MdHYL1 modulates cold tolerance and disease resistance in apple

Apple (Malus domestica) trees often experience various abiotic and biotic stresses. However, due to the long juvenile period of apple and its high degree of genetic heterozygosity, only limited progress has been made in developing cold-hardy and disease-resistant cultivars through traditional approaches. Numerous studies reveal that biotechnology is a feasible approach to improve stress tolerance in woody perennial plants. HYPONASTIC LEAVES1 (HYL1), a double-stranded RNA-binding protein, is a key regulator involved in apple drought stress response. However, whether HYL1 participates in apple cold response and pathogen resistance remains unknown. In this study, we revealed that MdHYL1 plays a positive role in cold tolerance and pathogen resistance in apple. MdHYL1 acted upstream to positively regulate freezing tolerance and Alternaria alternata resistance by positively modulating transcripts of MdMYB88 and MdMYB124 in response to cold stress or A. alternata infection. In addition, MdHYL1 regulated the biogenesis of several miRNAs responsive to cold and A. alternata infection in apple. Furthermore, we identified Mdm-miRNA156 (Mdm-miR156) as a negative regulator of cold tolerance and Mdm-miRNA172 (Mdm-miR172) as a positive regulator of cold tolerance, and that Mdm-miRNA160 (Mdm-miR160) decreased plant resistance to infection by A. alternata. In summary, we highlight the molecular role of MdHYL1 regarding cold tolerance and A. alternata infection resistance, thereby providing candidate genes for breeding apple with freezing tolerance and A. alternata resistance using biotechnology.

Identification of the inducible activity in the promoter of the soybean BBI-DII gene exposed to abiotic stress or abscisic acid

The expression of the soybean Bowman-Birk proteinase isoinhibitor DII (BBI-DII) gene and the inducible activity of its promoter were studied under salt, drought, low temperature, and abscisic acid (ABA) exposure conditions. The BBI-DII gene was induced by salt, drought, low temperature, and ABA, and the relative expression levels were 103.09-, 107.01-, 17.25- and 27.24-fold, respectively, compared with the untreated control. The putative promoter, designated BP1 (- 1255 to + 872 bp), located 5'-upstream of the BBI-DII gene was cloned. The expression of the GUS gene in pCAM-BP1 transgenic tobacco plants was highest at 5 h after treatment with salt, drought, low temperature and ABA, especially under salt and drought. Using histochemical staining and fluorescence analysis of GUS, BP1 activity under salt and drought conditions after 5 h was 1.03 and 1.07-fold, respectively, compared with that of the CaMV35S promoter. Based on a 5' deletion analysis, the segment (+ 41 to + 474 bp) was the basal region that responded to salt and drought, whereas the segment (- 820 to + 41 bp) was the area that responded to increased salt and drought activity. The BP2 (- 820 to + 872) activities were 0.98- and 1.02-fold compared with that of BP1 under salt and drought conditions and was 435 bp shorter than BP1. The salt- and drought-inducible activities of the BP2 promoter in the roots, stems, and leaves of transgenic tobacco plants were stable. Taken together, BP2 is more suitable than the BP1 promoter for the study and molecular breeding of stress-resistant soybean plants.

Genome-wide identification and expression analysis of MYB gene family in Cajanus cajan and CcMYB107 improves plant drought tolerance

MYB transcription factor (TF) is one of the largest superfamilies that play a vital role in multiple plant biological processes. However, the MYB family has not been comprehensively identified and functionally verified in Cajanus cajan, which is the sixth most important legume crop. Here, 170 CcR2R3-MYBs were identified and divided into 43 functional subgroups. Segmental and tandem duplications and alternative splicing events were found and promoted the expansion of the CcR2R3-MYB gene family. Functional prediction results showed that CcR2R3-MYBs were mainly involved in secondary metabolism, cell fate and identity, developmental processes, and responses to abiotic stress. Cis-acting element analysis of promoters revealed that stress response elements were widespread in the above four functional branches, further suggesting CcR2R3-MYBs were extensively involved in abiotic stress response. The transcriptome data and qRT-PCR results indicated that most of the CcR2R3-MYB genes responded to various stresses, of which the expression of CcMYB107 was significantly induced by drought stress. Overexpression of CcMYB107 enhanced antioxidant enzyme activity and increased proline and lignin accumulation, thus improving the drought resistance of C. cajan. Furthermore, Overexpression of CcMYB107 up-regulated the expression of stress-related genes and lignin biosynthesis genes after drought stress. Our findings established a strong foundation for the investigation of biological function of CcR2R3-MYB TFs in C. cajan.

Characterization of myo-inositol oxygenase from rice (OsMIOX): influence of salinity stress in different indica rice cultivars

Myo-inositol oxygenase (MIOX), the only catabolic enzyme of the inositol pathway, catalyzes conversion of myo-inositol to D-GlcA (glucuronic acid). The present study encompasses bioinformatic analysis of MIOX gene across phylogenetically related plant lineages and representative animal groups. Comparative motif analysis of the MIOX gene(s) across various plant groups suggested existence of abiotic- stress related cis-acting elements such as, DRE, MYB, MYC, STRE, MeJa among others. A detailed analysis revealed a single isoform of MIOX gene, located in chromosome 6 of indica rice (Oryza sativa) with an open reading frame of 938 bp coding for 308 amino acids producing a protein of ~ 35 kD. Secondary structure prediction of the protein gave the predicted number of 144 alpha helices and 154 random coils. The three-dimensional structure suggested it to be a monomeric protein with a single domain. Bacterial overexpression of the protein, purification and enzyme assay showed optimal catalytic activity at pH 7.5-8 at an optimal temperature of 37 °C with Michaelis constant of 40.92 mM. The range of Km was determined as 22.74-28.7 mM and the range of Vmax was calculated as 3.51-3.6 µM/min, respectively. Four salt-tolerant and salt-sensitive rice cultivars displayed differential gene expression of OsMIOX at different time points in different tissues under salinity and drought stress as observed from qRT-PCR data, microarray results and protein expression profile in immunoblot analysis. Gel volumetric analysis confirmed a very high expression of MIOX in roots and leaves on 7th day following germination. Microarray data showed high expression of MIOX at all developmental stages including seedling growth and reproduction. These data suggest that OsMIOX might have a role to play in rice abiotic stress responses mediated through the myo-inositol oxidation pathway.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-023-01340-6.

Transcriptomic, Physiological, and Metabolomic Response of an Alpine Plant, Rhododendron delavayi, to Waterlogging Stress and Post-Waterlogging Recovery

Climate change has resulted in frequent heavy and prolonged rainfall events that exacerbate waterlogging stress, leading to the death of certain alpine Rhododendron trees. To shed light on the physiological and molecular mechanisms behind waterlogging stress in woody Rhododendron trees, we conducted a study of Rhododendron delavayi, a well-known alpine flower species. Specifically, we investigated the physiological and molecular changes that occurred in leaves of R. delavayi subjected to 30 days of waterlogging stress (WS30d), as well as subsequent post-waterlogging recovery period of 10 days (WS30d-R10d). Our findings reveal that waterlogging stress causes a significant reduction in CO₂ assimilation rate, stomatal conductance, transpiration rate, and maximum photochemical efficiency of PSII (Fv/Fm) in the WS30d leaves, by 91.2%, 95.3%, 93.3%, and 8.4%, respectively, when compared to the control leaves. Furthermore, the chlorophyll a and total chlorophyll content in the WS30d leaves decreased by 13.5% and 16.6%, respectively. Both WS30d and WS30d-R10d leaves exhibited excessive H₂O₂ accumulation, with a corresponding decrease in lignin content in the WS30d-R10d leaves. At the molecular level, purine metabolism, glutathione metabolism, photosynthesis, and photosynthesis-antenna protein pathways were found to be primarily involved in WS30d leaves, whereas phenylpropanoid biosynthesis, fatty acid metabolism, fatty acid biosynthesis, fatty acid elongation, and cutin, suberin, and wax biosynthesis pathways were significantly enriched in WS30d-R10d leaves. Additionally, both WS30d and WS30d-R10d leaves displayed a build-up of sugars. Overall, our integrated transcriptomic, physiological, and metabolomic analysis demonstrated that R. delavayi is susceptible to waterlogging stress, which causes irreversible detrimental effects on both its physiological and molecular aspects, hence compromising the tree's ability to fully recover, even under normal growth conditions.

Root and Leaf Anatomy, Ion Accumulation, and Transcriptome Pattern under Salt Stress Conditions in Contrasting Genotypes of Sorghum bicolor

Roots from salt-susceptible ICSR-56 (SS) sorghum plants display metaxylem elements with thin cell walls and large diameter. On the other hand, roots with thick, lignified cell walls in the hypodermis and endodermis were noticed in salt-tolerant CSV-15 (ST) sorghum plants. The secondary wall thickness and number of lignified cells in the hypodermis have increased with the treatment of sodium chloride stress to the plants (STN). Lignin distribution in the secondary cell wall of sclerenchymatous cells beneath the lower epidermis was higher in ST leaves compared to the SS genotype. Casparian thickenings with homogenous lignin distribution were observed in STN roots, but inhomogeneous distribution was evident in SS seedlings treated with sodium chloride (SSN). Higher accumulation of K⁺ and lower Na⁺ levels were noticed in ST compared to the SS genotype. To identify the differentially expressed genes among SS and ST genotypes, transcriptomic analysis was carried out. Both the genotypes were exposed to 200 mM sodium chloride stress for 24 h and used for analysis. We obtained 70 and 162 differentially expressed genes (DEGs) exclusive to SS and SSN and 112 and 26 DEGs exclusive to ST and STN, respectively. Kyoto Encyclopaedia of Genes and Genomes (KEGG) and Gene Ontology (GO) enrichment analysis unlocked the changes in metabolic pathways in response to salt stress. qRT-PCR was performed to validate 20 DEGs in each SSN and STN sample, which confirms the transcriptomic results. These results surmise that anatomical changes and higher K⁺/Na⁺ ratios are essential for mitigating salt stress in sorghum apart from the genes that are differentially up- and downregulated in contrasting genotypes.

Insights into the Transcriptomics of Crop Wild Relatives to Unravel the Salinity Stress Adaptive Mechanisms

The narrow genomic diversity of modern cultivars is a major bottleneck for enhancing the crop's salinity stress tolerance. The close relatives of modern cultivated plants, crop wild relatives (CWRs), can be a promising and sustainable resource to broaden the diversity of crops. Advances in transcriptomic technologies have revealed the untapped genetic diversity of CWRs that represents a practical gene pool for improving the plant's adaptability to salt stress. Thus, the present study emphasizes the transcriptomics of CWRs for salinity stress tolerance. In this review, the impacts of salt stress on the plant's physiological processes and development are overviewed, and the transcription factors (TFs) regulation of salinity stress tolerance is investigated. In addition to the molecular regulation, a brief discussion on the phytomorphological adaptation of plants under saline environments is provided. The study further highlights the availability and use of transcriptomic resources of CWR and their contribution to pangenome construction. Moreover, the utilization of CWRs' genetic resources in the molecular breeding of crops for salinity stress tolerance is explored. Several studies have shown that cytoplasmic components such as calcium and kinases, and ion transporter genes such as Salt Overly Sensitive 1 (SOS1) and High-affinity Potassium Transporters (HKTs) are involved in the signaling of salt stress, and in mediating the distribution of excess Na⁺ ions within the plant cells. Recent comparative analyses of transcriptomic profiling through RNA sequencing (RNA-Seq) between the crops and their wild relatives have unraveled several TFs, stress-responsive genes, and regulatory proteins for generating salinity stress tolerance. This review specifies that the use of CWRs transcriptomics in combination with modern breeding experimental approaches such as genomic editing, de novo domestication, and speed breeding can accelerate the CWRs utilization in the breeding programs for enhancing the crop's adaptability to saline conditions. The transcriptomic approaches optimize the crop genomes with the accumulation of favorable alleles that will be indispensable for designing salt-resilient crops.

Over-expression of CcMYB24, encoding a R2R3-MYB transcription factor from a high-leaf-number mutant of Cymbidium, increases the number of leaves in Arabidopsis

Ornamental foliage plants have long been cultivated for their attractive leaves. Variation in leaf traits of ornamental foliage plants is one of the goals in breeding. MYB transcription factors regulate many aspects of leaf development, and thus influence morphological traits of leaves. However, little is known about the function of MYB transcription factors in leaf development of Cymbidium, one of the most economically important ornamental plants in the world. In the present study, a MYB transcription factor, CcMYB24, was identified and the corresponding gene cloned from a new orchid mutant, TRIR-2, which produces more leaves than control plants. The CcMYB24 showed a higher expression level in 'TRIR-2' than in control plants, and the protein was located in the nucleus. The sequence of CcMYB24 showed a high similarity with RAX2-like genes which belong to the R2R3-MYB gene family in other Cymbidium plants. Overexpression of CcMYB24 resulted in a phenotype with an increased number of leaves, elevated chlorophyll content, and decreased contents of carotenoids and flavonoids in Arabidopsis. These results provide functional evidence for the role of CcMYB24 in promoting the production of leaves in 'TRIR-2'. Understanding the role of CcMYB24 in Cymbidium will be beneficial for the molecular breeding of ornamental foliage plants.

Cloning and Functional Characterization of Cold-Inducible MYB-like 17 Transcription Factor in Rapeseed (Brassica napus L.)

Rapeseed (Brassica napus L.) is an important crop for edible oil, vegetables, and biofuel. Rapeseed growth and development require a minimum temperature of ~1-3 °C. Notably, frost damage occurs during overwintering, posing a serious threat to the productivity and yield of rapeseed. MYB proteins are important transcription factors (TFs) in plants, and have been proven to be involved in the regulation of stress responses. However, the roles of the MYB TFs in rapeseed under cold stress conditions are yet to be fully elucidated. To better understand the molecular mechanisms of one MYB-like 17 gene, BnaMYBL17, in response to low temperature, the present study found that the transcript level of BnaMYBL17 is induced by cold stress. To characterize the gene's function, the 591 bp coding sequence (CDS) from rapeseed was isolated and stably transformed into rapeseed. The further functional analysis revealed significant sensitivity in BnaMYBL17 overexpression lines (BnaMYBL17-OE) after freezing stress, suggesting its involvement in freezing response. A total of 14,298 differentially expressed genes relative to freezing response were found based on transcriptomic analysis of BnaMYBL17-OE. Overall, 1321 candidate target genes were identified based on differential expression, including Phospholipases C1 (PLC1), FCS-like zinc finger 8 (FLZ8), and Kinase on the inside (KOIN). The qPCR results confirmed that the expression levels of certain genes showed fold changes ranging from two to six when compared between BnaMYBL17-OE and WT lines after exposure to freezing stress. Furthermore, verification indicated that BnaMYBL17 affects the promoter of BnaPLC1, BnaFLZ8, and BnaKOIN genes. In summary, the results suggest that BnaMYBL17 acts as a transcriptional repressor in regulating certain genes related to growth and development during freezing stress. These findings provide valuable genetic and theoretical targets for molecular breeding to enhance freezing tolerance in rapeseed.

Evaluating the Differential Response of Transcription Factors in Diploid versus Autotetraploid Rice Leaves Subjected to Diverse Saline-Alkali Stresses

Saline-alkali stress is a significant abiotic stress factor that impacts plant growth, development, and crop yield. Consistent with the notion that genome-wide replication events can enhance plant stress resistance, autotetraploid rice exhibited a higher level of tolerance to saline-alkali stress than its donor counterparts, which is reflected by differential gene expression between autotetraploid and diploid rice in response to salt, alkali, and saline-alkali stress. In this study, we investigated the expression of the transcription factors (TFs) in the leaf tissues of autotetraploid and diploid rice under different types of saline-alkali stress. Transcriptome analysis identified a total of 1040 genes from 55 TF families that were altered in response to these stresses, with a significantly higher number in autotetraploid rice compared to diploid rice. Contrarily, under these stresses, the number of expressed TF genes in autotetraploid rice was greater than that in diploid rice for all three types of stress. In addition to the different numbers, the differentially expressed TF genes were found to be from significantly distinct TF families between autotetraploid and diploid rice genotypes. The GO enrichment analysis unraveled that all the DEGs were distributed with differentially biological functions in rice, in particular those that were enriched in the pathways of phytohormones and salt resistance, signal transduction, and physiological and biochemical metabolism in autotetraploid rice compared to its diploid counterpart. This may provide useful guidance for studying the biological roles of polyploidization in plant resilience in response to saline-alkali stress.

Genome-Wide Identification and Analysis of R2R3-MYB Genes Response to Saline-Alkali Stress in Quinoa

Soil saline-alkalization inhibits plant growth and development and seriously affects crop yields. Over their long-term evolution, plants have formed complex stress response systems to maintain species continuity. R2R3-MYB transcription factors are one of the largest transcription factor families in plants, widely involved in plant growth and development, metabolism, and stress response. Quinoa (Chenopodium quinoa Willd.), as a crop with high nutritional value, is tolerant to various biotic and abiotic stress. In this study, we identified 65 R2R3-MYB genes in quinoa, which are divided into 26 subfamilies. In addition, we analyzed the evolutionary relationships, protein physicochemical properties, conserved domains and motifs, gene structure, and cis-regulatory elements of CqR2R3-MYB family members. To investigate the roles of CqR2R3-MYB transcription factors in abiotic stress response, we performed transcriptome analysis to figure out the expression file of CqR2R3-MYB genes under saline-alkali stress. The results indicate that the expression of the six CqMYB2R genes was altered significantly in quinoa leaves that had undergone saline-alkali stress. Subcellular localization and transcriptional activation activity analysis revealed that CqMYB2R09, CqMYB2R16, CqMYB2R25, and CqMYB2R62, whose Arabidopsis homologues are involved in salt stress response, are localized in the nucleus and exhibit transcriptional activation activity. Our study provides basic information and effective clues for further functional investigation of CqR2R3-MYB transcription factors in quinoa.

Genome-Wide Analysis of MYB Transcription Factors in the Wheat Genome and Their Roles in Salt Stress Response

Large and rapidly increasing areas of salt-affected soils are posing major challenges for the agricultural sector. Most fields used for the important food crop Triticum aestivum (wheat) are expected to be salt-affected within 50 years. To counter the associated problems, it is essential to understand the molecular mechanisms involved in salt stress responses and tolerance, thereby enabling their exploitation in the development of salt-tolerant varieties. The myeloblastosis (MYB) family of transcription factors are key regulators of responses to both biotic and abiotic stress, including salt stress. Thus, we used the Chinese spring wheat genome assembled by the International Wheat Genome Sequencing Consortium to identify putative MYB proteins (719 in total). Protein families (PFAM) analysis of the MYB sequences identified 28 combinations of 16 domains in the encoded proteins. The most common consisted of MYB_DNA-binding and MYB-DNA-bind_6 domains, and five highly conserved tryptophans were located in the aligned MYB protein sequence. Interestingly, we found and characterized a novel 5R-MYB group in the wheat genome. In silico studies showed that MYB transcription factors MYB3, MYB4, MYB13 and MYB59 are involved in salt stress responses. qPCR analysis confirmed upregulation of the expression of all these MYBs in both roots and shoots of the wheat variety BARI Gom-25 (except MYB4, which was downregulated in roots) under salt stress. Moreover, we identified nine target genes involved in salt stress that are regulated by the four MYB proteins, most of which have cellular locations and are involved in catalytic and binding activities associated with various cellular and metabolic processes.

Dissecting the features of TGA gene family in Saccharum and the functions of ScTGA1 under biotic stresses

Sugarcane is an important sugar and energy crop and smut disease caused by Sporisorium scitamineum is a major fungal disease which can seriously reduce the yield and quality of sugarcane. In plants, TGACG motif binding (TGA) transcription factors are involved in the regulation of salicylic acid (SA) and methyl jasmonate (MeJA) signaling pathways, as well as in response to various biotic and abiotic stresses. However, no TGA-related transcription factor has been reported in Saccharum. In the present study, 44 SsTGA genes were identified from Saccharum spontaneum, and were assorted into three clades (I, II, III). Cis-regulatory elements (CREs) analysis revealed that SsTGA genes may be involved in hormone and stress response. RNA-seq data and RT-qPCR analysis indicated that SsTGAs were constitutively expressed in different tissues and induced by S. scitamineum stress. In addition, a ScTGA1 gene (GenBank accession number ON416997) was cloned from the sugarcane cultivar ROC22, which was homologous to SsTGA1e in S. spontaneum and encoded a nucleus protein. It was constitutively expressed in sugarcane tissues and up-regulated by SA, MeJA and S. scitamineum stresses. Furthermore, transient overexpression of ScTGA1 in Nicotiana benthamiana could enhance its resistance to the infection of Ralstonia solanacearum and Fusarium solani var. coeruleum, by regulating the expression of immune genes related to hypersensitive response (HR), ethylene (ET), SA and jasmonic acid (JA) pathways. This study should contribute to our understanding on the evolution and function of the SsTGA gene family in Saccharum, and provide a basis for the functional identification of ScTGA1 under biotic stresses.

Genome-wide association analysis reveals the optimal genomic regions for pod size in bean

The snap bean is the most commonly grown vegetable legume worldwide, and its pod size is both an important yield and appearance quality trait. However, the improvement of pod size in snap beans grown in China has been largely hindered by a lack of information on the specific genes that determine pod size. In this study, we identified 88 snap bean accessions and evaluated their pod size traits. Through a genome-wide association study (GWAS), 57 single nucleotide polymorphisms (SNPs) significantly associated with pod size were detected. Candidate gene analysis showed that cytochrome P450 family genes, WRKY, and MYB transcription factors were the predominant candidate genes for pod development, and eight of these 26 candidate genes showed relatively higher expression patterns in flowers and young pods. A significant pod length (PL) SNP and a single pod weight (SPW) SNP were successfully converted into kompetitive allele-specific polymerase chain reaction (KASP) markers and validated in the panel. These results enhance our understanding of the genetic basis of pod size, and also provide genetic resources for the molecular breeding of pod size in snap beans.

Metabolite Profiling and Transcriptome Analysis Explain the Difference in Accumulation of Bioactive Constituents in Taxilli Herba from Two Hosts

Taxilli Herba (TH) is a semi-parasitic herb and the host is a key factor affecting its quality. Flavonoids are the main bioactive constituents in TH. However, studies on the difference in accumulation of flavonoids in TH from different hosts are vacant. In this study, integrated transcriptomic and metabolomic analyses were performed on TH from Morus alba L. (SS) and Liquidambar formosana Hance (FXS) to investigate the relationship between the regulation of gene expression and the accumulation of bioactive constituents. The results showed that a total of 3319 differentially expressed genes (DEGs) were screened in transcriptomic analysis, including 1726 up-regulated genes and 1547 down-regulated genes. In addition, 81 compounds were identified using ultra-fast performance liquid chromatography coupled with triple quadrupole-time of flight ion trap tandem mass spectrometry (UFLC-Triple TOF-MS/MS) analysis, and the relative contents of flavonol aglycones and glycosides were higher in TH from SS group than those from the FXS group. A putative biosynthesis network of flavonoids was created, combined with structural genes, and the expression patterns of genes were mostly consistent with the variation of bioactive constituents. It was noteworthy that the UDP-glycosyltransferase genes might participate in downstream flavonoid glycosides synthesis. The findings of this work will provide a new way to understand the quality formation of TH from the aspects of metabolite changes and molecular mechanism.

GhMYB44 enhances stomatal closure to confer drought stress tolerance in cotton and Arabidopsis

MYB genes play crucial roles in plant response to abiotic stress. However, the function of MYB genes in cotton during abiotic stress is less well elucidated. Here, we found an R2R3-type MYB gene, GhMYB44, was induced by simulated drought (PEG6000) and ABA in three cotton varieties. After drought stress, the GhMYB44-silenced plants showed substantial changes at the physiological level, including significantly increased malondialdehyde content and decreased SOD activity. Silencing the GhMYB44 gene increased stomatal aperture and water loss rate, reduced plant drought tolerance. Transgenic Arabidopsis thaliana over-expressed GhMYB44 (GhMYB44-OE) enhanced resistance to mannitol-simulated osmotic stress. The stomatal aperture of the GhMYB44-OE Arabidopsis was significantly smaller than those of the wild type (WT), and the GhMYB44-OE Arabidopsis increased tolerance to drought stress. Transgenic Arabidopsis had higher germination rate under ABA treatment compared to WT, and the transcript levels of AtABI1, AtPP2CA and AtHAB1 were suppressed in GhMYB44-OE plants, indicating a potential role of GhMYB44 in the ABA signal pathway. These results showed that GhMYB44 acts as a positive regulator in plant response to drought stress, potentially useful for engineering drought-tolerant cotton.

Proteasomal degradation of MaMYB60 mediated by the E3 ligase MaBAH1 causes high temperature-induced repression of chlorophyll catabolism and green ripening in banana

Banana (Musa acuminata) fruits ripening at 30 °C or above fail to develop yellow peels; this phenomenon, called green ripening, greatly reduces their marketability. The regulatory mechanism underpinning high temperature-induced green ripening remains unknown. Here we decoded a transcriptional and post-translational regulatory module that causes green ripening in banana. Banana fruits ripening at 30 °C showed greatly reduced expression of 5 chlorophyll catabolic genes (CCGs), MaNYC1 (NONYELLOW COLORING 1), MaPPH (PHEOPHYTINASE), MaTIC55 (TRANSLOCON AT THE INNER ENVELOPE MEMBRANE OF CHLOROPLASTS 55), MaSGR1 (STAY-GREEN 1), and MaSGR2 (STAY-GREEN 2), compared to those ripening at 20 °C. We identified a MYB transcription factor, MaMYB60, that activated the expression of all 5 CCGs by directly binding to their promoters during banana ripening at 20 °C, while showing a weaker activation at 30 °C. At high temperatures, MaMYB60 was degraded. We discovered a RING-type E3 ligase MaBAH1 (benzoic acid hypersensitive 1) that ubiquitinated MaMYB60 during green ripening and targeted it for proteasomal degradation. MaBAH1 thus facilitated MaMYB60 degradation and attenuated MaMYB60-induced transactivation of CCGs and chlorophyll degradation. By contrast, MaMYB60 upregulation increased CCG expression, accelerated chlorophyll degradation, and mitigated green ripening. Collectively, our findings unravel a dynamic, temperature-responsive MaBAH1-MaMYB60-CCG module that regulates chlorophyll catabolism, and the molecular mechanism underpinning green ripening in banana. This study also advances our understanding of plant responses to high-temperature stress.

Genome-wide characterization and expression analysis of α-amylase and β-amylase genes underlying drought tolerance in cassava

BACKGROUND

Starch hydrolysates are energy sources for plant growth and development, regulate osmotic pressure and transmit signals in response to both biological and abiotic stresses. The α-amylase (AMY) and the β-amylase (BAM) are important enzymes that catalyze the hydrolysis of plant starch. Cassava (Manihot esculenta Crantz) is treated as one of the most drought-tolerant crops. However, the mechanisms of how AMY and BAM respond to drought in cassava are still unknown.

RESULTS

Six MeAMY genes and ten MeBAM genes were identified and characterized in the cassava genome. Both MeAMY and MeBAM gene families contain four genes with alternative splicing. Tandem and fragment replications play important roles in the amplification of MeAMY and MeBAM genes. Both MeBAM5 and MeBAM10 have a BZR1/BES1 domain at the N-terminus, which may have transcription factor functions. The promoter regions of MeAMY and MeBAM genes contain a large number of cis-acting elements related to abiotic stress. MeAMY1, MeAMY2, MeAMY5, and MeBAM3 are proven as critical genes in response to drought stress according to their expression patterns under drought. The starch content, soluble sugar content, and amylase activity were significantly altered in cassava under different levels of drought stress.

CONCLUSIONS

These results provide fundamental knowledge for not only further exploring the starch metabolism functions of cassava under drought stress but also offering new perspectives for understanding the mechanism of how cassava survives and develops under drought.

Genome-Wide Identification and Analysis of MYB Transcription Factor Family in Hibiscus hamabo

MYB transcription factors constitute one of the largest gene families in plants and play essential roles in the regulation of plant growth, responses to stress, and a wide variety of physiological and biochemical processes. In this study, 204 MYB proteins (HhMYBs) were identified in the Hibiscus hamabo Sieb. et Zucc (H. hamabo) genome and systematically analyzed based on their genomic sequence and transcriptomic data. The candidate HhMYB proteins and MYBs of Arabidopsis thaliana were divided into 28 subfamilies based on the analysis of their phylogenetic relationships and their motif patterns. Expression analysis using RNA-seq and quantitative real-time PCR (qRT-PCR) indicated that most HhMYBs are differentially regulated under drought and salt stresses. qRT-PCR analysis of seven selected HhMYBs suggested that the HhMYB family may have regulatory roles in the responses to stress and hormones. This study provides a framework for a more comprehensive analysis of the role of MYBs in the response to abiotic stress in H. hamabo.

Large-scale analysis of putative Euphorbiaceae R2R3-MYB transcription factors identifies a MYB involved in seed oil biosynthesis

BACKGROUND

MYB transcription factors are widely distributed in the plant kingdom and play key roles in regulatory networks governing plant metabolism and biochemical and physiological processes.

RESULTS

Here, we first determined the R2R3-MYB genes in five Euphorbiaceae genomes. The three Trp (W) residues from the first MYB domain (R2) were absolutely conserved, whereas the first W residue from the second MYB domain (R3) was preferentially mutated. The R2R3-MYBs were clustered into 48 functional subfamilies, of which 34 had both R2R3-MYBs of Euphorbiaceae species and AtMYBs, and four contained only Euphorbiaceae R2R3-MYBs. The whole-genome duplication (WGD) and/or segmental duplication (SD) played key roles in the expansion of the R2R3-MYB family. Unlike paralogous R2R3-MYB family members, orthologous R2R3-MYB members contained a higher selective pressure and were subject to a constrained evolutionary rate. VfMYB36 was specifically expressed in fruit, and its trend was consistent with the change in oil content, indicating that it might be involved in oil biosynthesis. Overexpression experiments showed that VfMYB36 could significantly provide linolenic acid (C18:3) content, which eventually led to a significant increase in oil content.

CONCLUSION

Our study first provides insight into understanding the evolution and expression of R2R3-MYBs in Euphorbiaceae species, and also provides a target for the production of biomass diesel and a convenient way for breeding germplasm resources with high linolenic acid content in the future.

Phylogenetic Analysis of R2R3-MYB Family Genes in Tetrastigma hemsleyanum Diels et Gilg and Roles of ThMYB4 and ThMYB7 in Flavonoid Biosynthesis

Tetrastigma hemsleyanum Diels et Gilg (T. hemsleyanum) is an extensively used Chinese folk herb with multiple bioactivities. Among these bioactivities, flavonoids are recognized as the representative active ingredients. We previously found an elevated accumulation of flavonoids in T. hemsleyanum under water stress; however, the mechanism remains unclear. R2R3-MYB transcription factors play vital roles in the plant response to environmental stress and the regulation of secondary metabolites. Herein, a systematic transcriptome identification of R2R3-MYB family genes under water stress in T. hemsleyanum was performed to explore their potential function in the biosynthesis of flavonoids. A total of 26 R2R3-MYB genes were identified, most of which were clustered into functional branches of abiotic stress. ThMYB4 and ThMYB7 were then screened out to be associated with the biosynthesis of flavonoids through a protein-protein interaction prediction. An expression correlation analysis based on RNA-seq further confirmed that ThMYB4 and ThMYB7 were positively related to the flavonoid biosynthetic pathway genes of T. hemsleyanum. In ThMYB4- and ThMYB7-overexpression hairy roots, it was found that the expression of ThCHS and ThCHI was significantly increased, suggesting that ThMYB4 and ThMYB7 may act as regulators in flavonoid biosynthesis. This will shed new light on the promotion of flavonoid production and the medicinal value of T. hemsleyanum by manipulating transcription factors.

Genome-wide characterization and expression analysis of MYB transcription factors in Chrysanthemum nankingense

BACKGROUND

Chrysanthemum is a popular ornamental plant worldwide. MYB (v-myb avian myeloblastosis viral oncogene homolog) transcription factors play an important role in everything from stress resistance to plant growth and development. However, the MYB family of chrysanthemums has not been the subject of a detailed bioinformatics and expression investigation.

RESULTS

In this study, we examined 324 CnMYB transcription factors from Chrysanthemum nankingense genome data, which contained 122 Cn1R-MYB, 183 CnR2R3-MYB, 12 Cn3R-MYB, 2 Cn4R-MYB, and 5 atypical CnMYB. The protein motifs and classification of CnMYB transcription factors were analyzed. Among them, motifs 1, 2, 3, and 4 were found to encode the MYB DNA-binding domain in R2R3-MYB proteins, while in other-MYB proteins, the motifs 1, 2, 3, 4, 5, 6, 7, and 8 encode the MYB DNA-binding domain. Among all CnMYBs, 44 genes were selected due to the presence of CpG islands, while methylation is detected in three genes, including CnMYB9, CnMYB152, and CnMYB219. We analyzed the expression levels of each CnMYB gene in ray floret, disc floret, flower bud, leaf, stem, and root tissues. Based on phylogenetic analysis and gene expression analysis, three genes appeared likely to control cellulose and lignin synthesis in stem tissue, and 16 genes appeared likely to regulate flowering time, anther, pollen development, and flower color. Fifty-one candidate genes that may be involved in stress response were identified through phylogenetic, stress-responseve motif of promoter, and qRT-PCR analyses. According to genes expression levels under stress conditions, six CnMYB genes (CnMYB9, CnMYB172, CnMYB186, CnMYB199, CnMYB219, and CnMYB152) were identified as key stress-responsive genes.

CONCLUSIONS

This research provides useful information for further functional analysis of the CnMYB gene family in chrysanthemums, as well as offers candidate genes for further study of cellulose and lignin synthesis, flowering traits, salt and drought stress mechanism.

Genome-wide identification and expression analysis of the HVA22 gene family in cotton and functional analysis of GhHVA22E1D in drought and salt tolerance

The HVA22 family of genes, induced by abscisic acid and stress, encodes a class of stress response proteins with a conserved TB2/DP1/HVA22 domain that are unique among eukaryotes. Previous studies have shown that HVA22s play an important role in plant responses to abiotic stresses. In the present study, 34, 32, 16, and 17 HVA22s were identified in G. barbadense, G. hirsutum, G. arboreum, and G. raimondii, respectively. These HVA22 genes were classified into nine subgroups, randomly distributed on the chromosomes. Synteny analysis showed that the amplification of the HVA22s were mainly due to segmental duplication or whole genome replication (WGD). Most HVA22s promoter sequences contain a large number of drought response elements (MYB), defense and stress response elements (TC-rich repeats), and hormone response elements (ABRE, ERE, SARE, etc.), suggesting that HVA22s may respond to adversity stresses. Expression profiling demonstrated that most GhHVA22s showed a constitutive expression pattern in G. hirsutum and could respond to abiotic stresses such as salt, drought, and low temperature. Overexpression of GhHVA22E1D (GH_D07G0564) in Arabidopsis thaliana enhances salt and drought tolerance in Arabidopsis. Virus-induced gene silencing of GhHVA22E1D reduced salt and drought tolerance in cotton. This indicates that GhHVA22E1D plays an active role in the plant response to salt stress and drought stress. GhHVA22E1D may act in plant response to adversity by altering the antioxidant capacity of plants. This study provides valuable information for the functional genomic study of the HVA22 gene family in cotton. It also provides a reference for further elucidation of the functional studies of HVA22 in plant resistance to abiotic stress response.

Abiotic stress tolerance in plants: a fascinating action of defense mechanisms

Climate fluctuation mediated abiotic stress consequences loss in crop yields. These stresses have a negative impact on plant growth and development by causing physiological and molecular changes. In this review, we have attempted to outline recent studies (5 years) associated with abiotic stress resistance in plants. We investigated the various factors that contribute to coping with abiotic challenges, such as transcription factors (TFs), microRNAs (miRNAs), epigenetic changes, chemical priming, transgenic breeding, autophagy, and non-coding RNAs. Stress responsive genes are regulated mostly by TFs, and these can be used to enhance stress resistance in plants. Plants express some miRNA during stress imposition that act on stress-related target genes to help them survive. Epigenetic alterations govern gene expression and facilitate stress tolerance. Chemical priming enhances growth in plants by modulating physiological parameters. Transgenic breeding enables identification of genes involved in precise plant responses during stressful situations. In addition to protein coding genes, non-coding RNAs also influence the growth of the plant by causing alterations at gene expression levels. For achieving sustainable agriculture for a rising world population, it is crucial to develop abiotic-resistant crops with anticipated agronomical traits. To achieve this objective, understanding the diverse mechanisms by which plants protect themselves against abiotic stresses is imperative. This review emphasizes on recent progress and future prospects for abiotic stress tolerance and productivity in plants.

A MYB-related transcription factor from peanut, AhMYB30, improves freezing and salt stress tolerance in transgenic Arabidopsis through both DREB/CBF and ABA-signaling pathways

Abiotic stresses such as salinity and low temperature have serious impact on peanut growth and yield. The present work investigated the function of a MYB-related transcription factor gene AhMYB30 obtained from peanut under salt and low temperature stresses by transgenic methods. The results indicated that the overexpression of AhMYB30 in Arabidopsis could enhance the resistance of transgenic plants to freezing and salt stresses. The expression of stress-response genes RD29A (Response-to-Dehydration 29A), COR15A (Cold-Regulated 15A), KIN1 (Kinesin 1) and ABI2 (Abscisic acid Insensitive 2) increased in transgenic plants compared with in wild-type. Subcellular localization and transcriptional autoactivation validation demonstrated that AhMYB30 has essential features of transcription factors. Therefore, AhMYB30 may increase salt and freezing stress tolerance as the transcription factor (TF) in Arabidopsis through both DREB/CBF and ABA-signaling pathways. Our results lay the theoretical foundation for exploring stress resistance mechanisms of peanut and offering novel genetic resources for molecular breeding.

Genome-Wide Analysis of MYB Transcription Factors and Screening of MYBs Involved in the Red Color Formation in Rhododendron delavayi

Flower color is one of the crucial traits of ornamental plants. Rhododendron delavayi Franch. is a famous ornamental plant species distributed in the mountain areas of Southwest China. This plant has red inflorescence and young branchlets. However, the molecular basis of the color formation of R. delavayi is unclear. In this study, 184 MYB genes were identified based on the released genome of R. delavayi. These genes included 78 1R-MYB, 101 R2R3-MYB, 4 3R-MYB, and 1 4R-MYB. The MYBs were divided into 35 subgroups using phylogenetic analysis of the MYBs of Arabidopsis thaliana. The members of the same subgroup in R. delavayi had similar conserved domains and motifs, gene structures, and promoter cis-acting elements, which indicate their relatively conserved function. In addition, transcriptome based on unique molecular identifier strategy and color difference of the spotted petals, unspotted petals, spotted throat, unspotted throat, and branchlet cortex were detected. Results showed significant differences in the expression levels of R2R3-MYB genes. Weighted co-expression network analysis between transcriptome and chromatic aberration values of five types of red samples showed that the MYBs were the most important TFs involved in the color formation, of which seven were R2R3-MYB, and three were 1R-MYB. Two R2R3-MYB (DUH019226.1 and DUH019400.1) had the highest connectivity in the whole regulation network, and they were identified as hub genes for red color formation. These two MYB hub genes provide references for the study of transcriptional regulation of the red color formation of R. delavayi.

Defensive Resistance of Cowpea Vigna unguiculata Control Megalurothrips usitatus Mediated by Jasmonic Acid or Insect Damage

Vigna unguiculata is a vital vegetable crop in Southeast Asia, and Megalurothrips usitatus can cause huge damage to this crop. Enhancing the resistance of V. unguiculata against M. usitatus is a promising way to protect this crop; however, there is limited information regarding the mechanism underlying the resistance of V. unguiculata against M. usitatus. Here, a behavior assay was performed to explore the resistance of V. unguiculata against M. usitatus after insect damage or treatment by jasmonic acid (JA). Furthermore, transcriptome and metabonomics analysis was used to detect the putative mechanism underlying the resistance of V. unguiculata against M. usitatus. The pre-treatment of Vigna unguiculata with JA or infestation with Megalurothrips usitatus alleviated the damage resulting from the pest insect. We further identified differentially expressed genes and different metabolites involved in flavonoid biosynthesis and alpha-linolenic acid metabolism. Genes of chalcone reductase and shikimate O-hydroxycinnamoyltransferase involved in flavonoid biosynthesis, as well as lipoxygenase and acyl-CoA oxidase involved in alpha-linolenic acid metabolism, were upregulated in plants after herbivory or JA supplementation. The upregulation of these genes contributed to the high accumulation of metabolites involved in flavonoid biosynthesis and the alpha-linolenic acid metabolism pathway. These transcriptional and metabolite changes are potentially responsible for plant defense and a putative regulatory model is thus proposed to illustrate the cowpea defense mechanism against insect attack. Our study provides candidate targets for the breeding of varieties with resistance to insect herbivory by molecular technology.

Drought stress tolerance mechanisms and their potential common indicators to salinity, insights from the wild watermelon (Citrullus lanatus): A review

Climate change has escalated the effect of drought on crop production as it has negatively altered the environmental condition. Wild watermelon grows abundantly in the Kgalagadi desert even though the environment is characterized by minimal rainfall, high temperatures and intense sunshine during growing season. This area is also characterized by sandy soils with low water holding capacity, thus bringing about drought stress. Drought stress affects crop productivity through its effects on development and physiological functions as dictated by molecular responses. Not only one or two physiological process or genes are responsible for drought tolerance, but a combination of various factors do work together to aid crop tolerance mechanism. Various studies have shown that wild watermelon possess superior qualities that aid its survival in unfavorable conditions. These mechanisms include resilient root growth, timely stomatal closure, chlorophyll fluorescence quenching under water deficit as key physiological responses. At biochemical and molecular level, the crop responds through citrulline accumulation and expression of genes associated with drought tolerance in this species and other plants. Previous salinity stress studies involving other plants have identified citrulline accumulation and expression of some of these genes (chloroplast APX, Type-2 metallothionein), to be associated with tolerance. Emerging evidence indicates that the upstream of functional genes are the transcription factor that regulates drought and salinity stress responses as well as adaptation. In this review we discuss the drought tolerance mechanisms in watermelons and some of its common indicators to salinity at physiological, biochemical and molecular level.

NAC domain transcription factor gene GhNAC3 confers drought tolerance in plants

Abiotic stress seriously affects the growth, yield, and fiber quality of cotton. It is of great importance to cultivate drought-resistant and salt-tolerant cotton. NAC (NAM, ATAF1/2, and CUC2) is a plant-specific transcription factor, which is widely involved in the response to abiotic stress. Here, we discovered the GhNAC3 gene isolated from the expression profile of drought stress in cotton and verified its functions in cotton. First, GhNAC3 was strongly induced expression by drought and salt stresses. Gene structure analysis revealed that GhNAC3 had a conserved NAC domain and was homologous to several stress-related NAC transcription factors gene of Arabidopsis. Subcellular localization and transcriptional activation assays revealed that GhNAC3 was a nuclear protein with a C-terminal transcriptional activation domain. Overexpression of GhNAC3 enhanced Arabidopsis tolerance to drought stress with reduced sensitivity to ABA, characterized by increased germination and cotyledon rates under drought stress, and promoted root elongation. VIGS silencing of GhNAC3 reduced cotton tolerance to drought stress as indicated by the low water content of the leaves under drought treatment, significantly faster water loss and lower ABA content in detached leaves, along with the accumulation of more hydrogen peroxide (H₂O₂) and malondialdehyde (MDA). In conclusion, GhNAC3 plays an important role in the abiotic stress of cotton, which might have great application potential in molecular breeding of cotton varieties with drought resistance.

A MYB Transcription Factor Atlas Provides Insights into the Evolution of Environmental Adaptations in Plants

The MYB transcription factor superfamily includes key regulators of plant development and responses to environmental changes. The diversity of lifestyles and morphological characteristics exhibited by plants are potentially associated with the genomic dynamics of the MYB superfamily. With the release of the plant genomes, a comprehensive phylogenomic analysis of the MYB superfamily across Viridiplantae is allowed. The present study performed phylogenetic, phylogenomic, syntenic, horizontal gene transfer, and neo/sub-functionalization analysis of the MYB superfamily to explore the evolutionary contributions of MYB members to species diversification, trait formation, and environmental adaptation in 437 different plant species. We identified major changes in copy number variation and genomic context within subclades across lineages. Multiple MYB subclades showed highly conserved copy number patterns and synteny across flowering plants, whereas others were more dynamic and showed lineage-specific patterns. As examples of lineage-specific morphological divergence, we hypothesize that the gain of a MYB orthogroup associated with flower development and environmental responses and an orthogroup associated with auxin and wax biosynthesis in angiosperms were correlated with the emergence of flowering plants, unbiased neo-/sub-functionalization of gene duplicates contributed to environmental adaptation, and species-specific neo-/sub-functionalization contributed to phenotype divergence between species. Transposable element insertion in promoter regions may have facilitated the sub-/neo-functionalization of MYB genes and likely played a tissue-specific role contributing to sub-/neo-functionalization in plant root tissues. This study provides new insights into the evolutionary divergence of the MYB superfamily across major flowering and non-flowering lineages and emphasizes the need for lineage-/tissue-specific characterization to further understand trait variability and environmental adaptation.

Genome-wide analysis and identification of microRNAs in Medicago truncatula under aluminum stress

Numerous studies have shown that plant microRNAs (miRNAs) play key roles in plant growth and development, as well as in response to biotic and abiotic stresses; however, the role of miRNA in legumes under aluminum (Al) stress have rarely been reported. Therefore, here, we aimed to investigate the role of miRNAs in and their mechanism of Al tolerance in legumes. To this end, we sequenced a 12-strand-specific library of Medicago truncatula under Al stress. A total of 195.80 M clean reads were obtained, and 876 miRNAs were identified, of which, 673 were known miRNAs and 203 were unknown. A total of 55 miRNAs and their corresponding 2,502 target genes were differentially expressed at various time points during Al stress. Further analysis revealed that mtr-miR156g-3p was the only miRNA that was significantly upregulated at all time points under Al stress and could directly regulate the expression of genes associated with root cell growth. Three miRNAs, novel_miR_135, novel_miR_182, and novel_miR_36, simultaneously regulated the expression of four Al-tolerant transcription factors, GRAS, MYB, WRKY, and bHLH, at an early stage of Al stress, indicating a response to Al stress. In addition, legume-specific miR2119 and miR5213 were involved in the tolerance mechanism to Al stress by regulating F-box proteins that have protective effects against stress. Our results contribute to an improved understanding of the role of miRNAs in Al stress in legumes and provide a basis for studying the molecular mechanisms of Al stress regulation.

Integration of meta-analysis, machine learning and systems biology approach for investigating the transcriptomic response to drought stress in Populus species

In Populus, drought is a major problem affecting plant growth and development which can be closely reflected by corresponding transcriptomic changes. Nevertheless, how these changes in Populus are not fully understood. Here, we first used meta-analysis and machine learning methods to identify water stress-responsive genes and then performed a systematic approach to discover important gene networks. Our analysis revealed that large transcriptional variations occur during drought stress. These changes were more associated with the response to stress, cellular catabolic process, metabolic pathways, and hormone-related genes. The differential gene coexpression analysis highlighted two acetyltransferase NATA1-like and putative cytochrome P450 genes that have a special contribution in response to drought stress. In particular, the findings showed that MYBs and MAPKs have a prominent role in the drought stress response that could be considered to improve the drought tolerance of Populus. We also suggest ARF2-like and PYL4-like genes as potential markers for use in breeding programs. This study provides a better understanding of how Populus responses to drought that could be useful for improving tolerance to stress in Populus.

MYB Transcription Factor Family in Pearl Millet: Genome-Wide Identification, Evolutionary Progression and Expression Analysis under Abiotic Stress and Phytohormone Treatments

Transcription factors (TFs) are the regulatory proteins that act as molecular switches in controlling stress-responsive gene expression. Among them, the MYB transcription factor family is one of the largest TF family in plants, playing a significant role in plant growth, development, phytohormone signaling and stress-responsive processes. Pearl millet (Pennisetum glaucum L.) is one of the most important C4 crop plants of the arid and semi-arid regions of Africa and Southeast Asia for sustaining food and fodder production. To explore the evolutionary mechanism and functional diversity of the MYB family in pearl millet, we conducted a comprehensive genome-wide survey and identified 279 MYB TFs (PgMYB) in pearl millet, distributed unevenly across seven chromosomes of pearl millet. A phylogenetic analysis of the identified PgMYBs classified them into 18 subgroups, and members of the same group showed a similar gene structure and conserved motif/s pattern. Further, duplication events were identified in pearl millet that indicated towards evolutionary progression and expansion of the MYB family. Transcriptome data and relative expression analysis by qRT-PCR identified differentially expressed candidate PgMYBs (PgMYB2, PgMYB9, PgMYB88 and PgMYB151) under dehydration, salinity, heat stress and phytohormone (ABA, SA and MeJA) treatment. Taken together, this study provides valuable information for a prospective functional characterization of the MYB family members of pearl millet and their application in the genetic improvement of crop plants.