VcMYB4a, an R2R3-MYB transcription factor from Vaccinium corymbosum, negatively regulates salt, drought, and temperature stress

Characterization and functions of Myeloblastosis (MYB) transcription factors in cucurbit crops

Myeloblastosis (MYB) is one of the largest family of transcription factors (TFs) in plants. It plays a key role in plant life activities, such as metabolic regulation, stress resistant, as well as helpful for plant growth and development. In China, cucurbit is an important and nutrients rich vegetable crop, which have high medicinal and socio-economic values. In this review, we discussed the structure and characterization of MYB TFs and how do regulate flower development, fruit maturity, fruit quality, and flavonoid biosynthesis. Furthermore, we highlight the effect and contribution of MYB TFs in the regulation of biotic and abiotic stress resistance. This comprehensive review will provide a new reference for the more effective application of MYB TF in quality control, stress resistance research and molecular breeding of cucurbit crops.

Genome-wide identification of the WRKY gene family in blueberry (Vaccinium spp.) and expression analysis under abiotic stress

Introduction

The WRKY transcription factor (TF) family is one of the largest TF families in plants and is widely involved in responses to both biotic and abiotic stresses.

Methods

To clarify the function of the WRKY family in blueberries, this study identified the WRKY genes within the blueberry genome and systematically analyzed gene characteristics, phylogenetic evolution, promoter cis-elements, expression patterns, and subcellular localization of the encoded products.

Results

In this study, 57 VcWRKY genes were identified, and all encoding products had a complete WRKY heptapeptide structure and zinc-finger motif. The VcWRKY genes were divided into three subgroups (I-III) by phylogenetic analysis. Group II was divided into five subgroups: IIa, IIb, IIc, IId, and IIe. 57 VcWRKY genes were distributed unevenly across 32 chromosomes. The amino acids ranged from 172 to 841, and molecular weights varied from 19.75 to 92.28 kD. Intra-group syntenic analysis identified 12 pairs of duplicate segments. Furthermore, 34 cis-element recognition sites were identified in the promoter regions of VcWRKY genes, primarily comprising phytohormone-responsive and light-responsive elements. Comparative syntenic maps were generated to investigate the evolutionary relationships of VcWRKY genes, revealing the closest homology to dicotyledonous WRKY gene families. VcWRKY genes were predominantly expressed in the fruit flesh and roots of blueberries. Gene expression analysis showed that the responses of VcWRKY genes to stress treatments were more strongly in leaves than in roots. Notably, VcWRKY13 and VcWRKY25 exhibited significant upregulation under salt stress, alkali stress, and saline-alkali stress, and VcWRKY1 and VcWRKY13 showed notable induction under drought stress. Subcellular localization analysis confirmed that VcWRKY13 and VcWRKY25 function within the nucleus.

Conclusion

These findings establish a foundation for further investigation into the functions and regulatory mechanisms of VcWRKY genes and provide guidance for selecting stress-tolerant genes in the development of blueberry cultivars.

Transcription factor CmHSFA4-CmMYBS3 complex enhances salt tolerance in chrysanthemum by repressing CmMYB121 expression

Excessive soil salinity not only hampers plant growth and development but can also lead to plant death. Previously, we found that heat-shock factor A4 (CmHSFA4) enhances the tolerance of chrysanthemum (Chrysanthemum morifolium) to salt. However, the underlying molecular mechanism remains unclear. In this study, we identified a candidate MYB transcription factor, CmMYB121, which responded to salt stress. We observed that the CmMYB121 transcription is suppressed by CmHSFA4. Moreover, overexpression of CmMYB121 exacerbated chrysanthemum sensitivity to salt stress. CmHSFA4 directly bound to the promoter of CmMYB121 at the heat-shock element. Protein-protein interaction assays identified an interaction between CmHSFA4 and CmMYBS3, a transcriptional repressor, and recruited the corepressor TOPLESS (CmTPL) to inhibit CmMYB121 transcription by impairing the H3 and H4 histone acetylation levels of CmMYB121. Our study demonstrated that a CmHSFA4-CmMYBS3-CmTPL complex modulates CmMYB121 expression, consequently regulating the tolerance of chrysanthemum to salt. The findings shed light on the responses of plants to salt stress.

SlGAD2 is the target of SlTHM27, positively regulates cold tolerance by mediating anthocyanin biosynthesis in tomato

Cold stress significantly limits the yield and quality of tomato. Deciphering the key genes related to cold tolerance is important for selecting and breeding superior cold-tolerant varieties. γ-aminobutyric acid (GABA) responds to various types of stress by rapidly accumulating in plant. In this study, glutamic acid decarboxylase (GAD2) was a positive regulator to enhance cold stress tolerance of tomato. Overexpression of SlGAD2 decreased the extent of cytoplasmic membrane damage and increased the endogenous GABA content, antioxidant enzyme activities, and reactive oxygen species (ROS) scavenging capacity in response to cold stress, whereas Slgad2 mutant plants showed the opposite trend. In addition, SlGAD2 induced anthocyanin biosynthesis in response to cold stress by increasing the content of endogenous GABA. Further study revealed that SlGAD2 expression was negatively regulated by the transcription factor SlTHM27. However, the transcript levels of SlTHM27 were repressed under cold stress. Antioxidant enzyme activities, SlGAD2 transcript levels, GABA and anthocyanin contents were significantly increased in Slthm27 mutant plants. Further, our study demonstrated that SlTHM27 decreases SlGAD2-promoted cold resistance in tomato by repressing SlGAD2 transcription. Overall, our results showed that the SlTHM27-SlGAD2 model regulates the cold tolerance in tomato by regulating GABA and anthocyanin.

Review on blueberry drought tolerance from the perspective of cultivar improvement

Blueberry (Vaccinium spp.) is an increasingly popular fruit around the world for their attractive taste, appearance, and most importantly their many health benefits. Global blueberry production was valued at $2.31 billion with the United States alone producing $1.02 billion of cultivated blueberries in 2021. The sustainability of blueberry production is increasingly threatened by more frequent and extreme drought events caused by climate change. Blueberry is especially prone to adverse effects from drought events due to their superficial root system and lack of root hairs, which limit blueberry's ability to intake water and nutrients from the soil especially under drought stress conditions. The goal of this paper is to review previous studies on blueberry drought tolerance focusing on physiological, biochemical, and molecular drought tolerance mechanisms, as well as genetic variability present in cultivated blueberries. We also discuss limitations of previous studies and potential directions for future efforts to develop drought-tolerant blueberry cultivars. Our review showed that the following areas are lacking in blueberry drought tolerance research: studies of root and fruit traits related to drought tolerance, large-scale cultivar screening, efforts to understand the genetic architecture of drought tolerance, tools for molecular-assisted drought tolerance improvement, and high-throughput phenotyping capability for efficient cultivar screening. Future research should be devoted to following areas: (1) drought tolerance evaluation to include a broader range of traits, such as root architecture and fruit-related performance under drought stress, to establish stronger association between physiological and molecular signals with drought tolerance mechanisms; (2) large-scale drought tolerance screening across diverse blueberry germplasm to uncover various drought tolerance mechanisms and valuable genetic resources; (3) high-throughput phenotyping tools for drought-related traits to enhance the efficiency and affordability of drought phenotyping; (4) identification of genetic architecture of drought tolerance using various mapping technologies and transcriptome analysis; (5) tools for molecular-assisted breeding for drought tolerance, such as marker-assisted selection and genomic selection, and (6) investigation of the interactions between drought and other stresses such as heat to develop stress resilient genotypes.

Integrated Transcriptomic and Metabolomics Analyses Reveal Molecular Responses to Cold Stress in Coconut (Cocos nucifera L.) Seedlings

Coconut is an important tropical and subtropical fruit and oil crop severely affected by cold temperature, limiting its distribution and application. Thus, studying its low-temperature reaction mechanism is required to expand its cultivation range. We used growth morphology and physiological analyses to characterize the response of coconuts to 10, 20, and 30 d of low temperatures, combined with transcriptome and metabolome analysis. Low-temperature treatment significantly reduced the plant height and dry weight of coconut seedlings. The contents of soil and plant analyzer development (SPAD), soluble sugar (SS), soluble protein (SP), proline (Pro), and malondialdehyde (MDA) in leaves were significantly increased, along with the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and the endogenous hormones abscisic acid (ABA), auxin (IAA), zeatin (ZR), and gibberellin (GA) contents. A large number of differentially expressed genes (DEGs) (9968) were detected under low-temperature conditions. Most DEGs were involved in mitogen-activated protein kinase (MAPK) signaling pathway-plant, plant hormone signal transduction, plant-pathogen interaction, biosynthesis of amino acids, amino sugar and nucleotide sugar metabolism, carbon metabolism, starch and sucrose metabolism, purine metabolism, and phenylpropanoid biosynthesis pathways. Transcription factors (TFs), including WRKY, AP2/ERF, HSF, bZIP, MYB, and bHLH families, were induced to significantly differentially express under cold stress. In addition, most genes associated with major cold-tolerance pathways, such as the ICE-CBF-COR, MAPK signaling, and endogenous hormones and their signaling pathways, were significantly up-regulated. Under low temperatures, a total of 205 differentially accumulated metabolites (DAMs) were enriched; 206 DAMs were in positive-ion mode and 97 in negative-ion mode, mainly including phenylpropanoids and polyketides, lipids and lipid-like molecules, benzenoids, organoheterocyclic compounds, organic oxygen compounds, organic acids and derivatives, nucleosides, nucleotides, and analogues. Comprehensive metabolome and transcriptome analysis revealed that the related genes and metabolites were mainly enriched in amino acid, flavonoid, carbohydrate, lipid, and nucleotide metabolism pathways under cold stress. Together, the results of this study provide important insights into the response of coconuts to cold stress, which will reveal the underlying molecular mechanisms and help in coconut screening and breeding.

Function of Transcription Factors PoMYB12, PoMYB15, and PoMYB20 in Heat Stress and Growth of Pleurotus ostreatus

MYB transcription factors (TFs) have been extensively studied in plant abiotic stress responses and growth and development. However, the role of MYB TFs in the heat stress response and growth and development of Pleurotus ostreatus remains unclear. To investigate the function of PoMYB12, PoMYB15, and PoMYB20 TFs in P. ostreatus, mutant strains of PoMYB12, PoMYB15, and PoMYB20 were generated using RNA interference (RNAi) and overexpression (OE) techniques. The results indicated that the mycelia of OE-PoMYB12, OE-PoMYB20, and RNAi-PoMYB15 mutant strains exhibited positive effects under heat stress at 32 °C, 36 °C, and 40 °C. Compared to wild-type strains, the OE-PoMYB12, OE-PoMYB20, and RNAi-PoMYB15 mutant strains promoted the growth and development of P. ostreatus. These mutant strains also facilitated the recovery of growth and development of P. ostreatus after 24 h of 36 °C heat stress. In conclusion, the expression of PoMYB12 and PoMYB20 supports the mycelium's response to heat stress and enhances the growth and development of P. ostreatus, whereas PoMYB15 produces the opposite effect.

An Efficient Transformation System for Fast Production of VcCHS Transgenic Blueberry Callus and Its Expressional Analysis

The Agrobacterium tumefaciens-mediated transformation for blueberries remains less efficient than is desirable. A new leaf callus regeneration and genetic transformation system was investigated in blueberries in this study. The leaf explants of cv. 'Legacy' and 'Northland' were used to establish the stable callus induction system when placed on the woody plant medium (WPM) supplemented with 1.0 mg·L-1 2, 4-D, 0.4 mg·L-1 6-BA for 30 d; then, the callus was sub-cultured in the proliferation medium supplemented with 1.5 mg·L-1 2, 4-D, 0.4 mg·L-1 6-BA in the darkness at 25 °C every 30 days. The co-cultivation of callus with A. tumefaciens was operated on WPM plus 100 μM acetosyringone for 4 days; then, the transferred callus was grown in WPM supplemented with 1.5 mg·L-1 2,4-D, 0.4 mg·L-1 6-BA, 50 mg·L-1 hygromycin, and 200 mg·L-1 cefotaxime. The VcCHS transgenic blueberry callus with both GFP signal and Hyg resistance was obtained from the transformed callus of cv. 'Northland'. The rate of GFP signal detected in the transformed callus was as high as 49.02%, which was consistent with the PCR assay. Collectively, this study provides a highly efficient genetic transformation system in blueberry callus and a powerful approach for the molecular breeding of blueberries.

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.

CgMYB1, an R2R3-MYB transcription factor, can alleviate abiotic stress in an annual halophyte Chenopodium glaucum

MYB transcription factors (TFs) are important regulators of the stress response in plants. In the present study, we characterized the CgMYB1 gene in Chenopodium glaucum, a member of the R2R3-MYB TF family. CgMYB1 was located in the nucleus with an activating domain at the C terminus. The CgMYB1 gene could be induced by salt and cold stress in C. glaucum. Overexpressing CgMYB1 in Arabidopsis significantly enhanced salt and cold tolerance, probably by improving physiological performance and stress-related gene expression. Further analysis suggests that the positive response of CgMYB1 to abiotic stress may partially be attributed to the interaction between CgMYB1 and the CgbHLH001 promoter followed by activation of downstream stress-responsive genes, which mediates stress tolerance. Our findings should contribute to further understanding of the function of R2R3 MYB TF in response to abiotic stress.

Transcriptomic and metabolomic insights on the molecular mechanisms of flower buds in responses to cold stress in two Camellia oleifera cultivars

INTRODUCTION

The Camellia oleifera (C. oleifera) cultivars 'Huashuo' (HS) and 'Huaxin' (HX) are new high-yielding and economically valuable cultivars that frequently encounter prolonged cold weather during the flowering period, resulting in decreased yields and quality. The flower buds of HS sometimes fail to open or open incompletely under cold stress, whereas the flower buds of HX exhibit delayed opening but the flowers and fruits rarely drop.

METHODS

In this study, flower buds at the same development stage of two C. oleifera cultivars were used as test materials for a combination of physiological, transcriptomic and metabolomic analyses, to unravel the different cold regulatory mechanisms between two cultivars of C. oleifera.

RESULTS AND DISCUSSION

Key differentially expressed genes (DEGs) and differentially expressed metabolites (DEMs) involved in sugar metabolism, phenylpropanoid biosynthesis, and hormone signal transduction were significantly higher in HX than in HS, which is consistent with phenotypic observations from a previous study. The results indicate that the flower buds of HX are less affected by long-term cold stress than those of HS, and that cold resistance in C. oleifera cultivars varies among tissues or organs.This study will provide a basis for molecular markers and molecular breeding of C. oleifera.

MYB pathways that regulate UV-B-induced anthocyanin biosynthesis in blueberry (Vaccinium corymbosum)

Ultraviolet-B (UV-B) promotes anthocyanin accumulation and improves fruit quality in plants. To explore the underlying network of MYB transcription factors that regulates UV-B-induced anthocyanin biosynthesis in blueberry (Vaccinium corymbosum), we analyzed the response of MYB transcription factor genes to UV-B treatment. Transcriptome sequencing analysis revealed that VcMYBA2 and VcMYB114 expression were upregulated and were positively correlated with the expression of anthocyanin structural genes under UV-B radiation according to weighted gene co-expression network analysis (WGCNA) data. The VcUVR8-VcCOP1-VcHY5 pathway perceives UV-B signals and promotes the expression of anthocyanin structural genes by upregulating VcMYBA2 and VcMYB114 or by regulating the VcBBXs-VcMYB pathway, ultimately promoting anthocyanin accumulation. By contrast, VcMYB4a and VcUSP1 were downregulated under UV-B treatment, and VcMYB4a expression was negatively correlated with that of anthocyanin biosynthesis genes in response to UV-B. Analysis of VcMYB4a-overexpressing and wild-type blueberry calli exposed to UV-B radiation revealed that VcMYB4a represses UV-B-induced anthocyanin accumulation. Yeast one-hybrid and dual luciferase assays showed that the universal stress protein VcUSP1 directly bound to the promoter of VcMYB4a. These results suggest that the VcUSP1-VcMYB4a pathway negatively regulates UV-B-induced anthocyanin biosynthesis and provide insight into UV-B-induced anthocyanin biosynthesis.

VaMYB44 transcription factor from Chinese wild Vitis amurensis negatively regulates cold tolerance in transgenic Arabidopsis thaliana and V. vinifera

Heterologous expression of VaMYB44 gene in Arabidopsis and V. vinifera cv. 'Thompson Seedless' increases cold sensitivity, which is mediated by the interaction of VaMYC2 and VaTIFY5A with VaMYB44 MYB transcription factors play critical roles in plant stress response. However, the function of MYB44 under low temperature stress is largely unknown in grapes. Here, we isolated a VaMYB44 gene from Chinese wild Vitis amurensis acc. 'Shuangyou' (cold-resistant). The VaMYB44 is expressed in various organs and has lower expression levels in stems and young leaves. Exposure of the cold-sensitive V. vinifera cv. 'Thompson Seedless' and cold-resistant 'Shuangyou' grapevines to cold stress (-1 °C) resulted in differential expression of MYB44 in leaves with the former reaching 14 folds of the latter after 3 h of cold stress. Moreover, the expression of VaMYB44 was induced by exogenous ethylene, abscisic acid, and methyl jasmonate in the leaves of 'Shuangyou'. Notably, the subcellular localization assay identified VaMYB44 in the nucleus. Interestingly, heterologous expression of VaMYB44 in Arabidopsis and 'Thompson Seedless' grape increased freezing-induced damage compared to their wild-type counterparts. Accordingly, the transgenic lines had higher malondialdehyde content and electrolyte permeability, and lower activities of superoxide dismutase, peroxidase, and catalase. Moreover, the expression levels of some cold resistance-related genes decreased in transgenic lines. Protein interaction assays identified VaMYC2 and VaTIFY5A as VaMYB44 interacting proteins, and VaMYC2 could bind to the VaMYB44 promoter and promote its transcription. In conclusion, the study reveals VaMYB44 as the negative regulator of cold tolerance in transgenic Arabidopsis and transgenic grapes, and VaMYC2 and VaTIFY5A are involved in the cold sensitivity of plants by interacting with VaMYB44.

Structural and interactions analysis of a transcription factor PnMYB2 in Panax notoginseng

The main active ingredients of the traditional Chinese medicinal plant, Panax notoginseng, are the Panax notoginseng saponins (PNS). They can be synthesized via the mevalonate pathway; PnSS and PnSE1 are the key rate-limiting enzymes in this pathway. In this study, an interaction between PnMYB2 and the key enzymes was identified and characterized from the P. notoginseng cDNA library using the Y1H technique. Subsequently, X-α-gal color reaction confirmed the interaction between PnMYB2 and the upstream sequences of PnSS and PnSE1 promoters. Full-length cDNA sequence of PnMYB2 was isolated and characterized. PnMYB2 has an open reading frame of 864 bp, encoding 287 amino acids. 3D structural analysis of PnMYB2 indicated that its structure was similar to that of the template. Phylogenetic analysis revealed that PnMYB2 and PgMYB2 are highly homologous and belong to the R2R3 MYB transcription factor (TF). Subcellular localization analysis showed that PnMYB2 was localized in the nucleus. The recombinant protein PnMYB2 was successfully obtained through prokaryotic expression and was confirmed to be an inclusion body protein. Furthermore, electrophoretic mobility shift assay (EMSA) experiments demonstrated that PnMYB2 specifically binds to MYB core and AC-rich elements. This study provides a theoretical basis for transcriptional regulation of saponin biosynthesis in P. notoginseng.

Identification and Expression Analysis of R2R3-MYB Family Genes Associated with Salt Tolerance in Cyclocarya paliurus

R2R3-MYB transcription factors are most abundant in the MYB superfamily, while the R2R3-MYB genes play an important role in plant growth and development, especially in response to environmental stress. Cyclocarya paliurus is a multifunction tree species, and the existing resources cannot meet the requirement for its leaf production and medical use. Therefore, lands with some environmental stresses would be potential sites for developing C. paliurus plantations. However, the function of R2R3-MYB genes in C.paliurus in response to environmental stress remains unknown. In this study, to identify the roles of R2R3-MYB genes associated with salt stress response, 153 CpaMYB genes and their corresponding protein sequences were identified from the full-length transcriptome. Based on the comparison with MYB protein sequences of Arabidopsis thaliana, 69 R2R3-MYB proteins in C. paliurus were extracted for further screening combined with conserved functional domains. Furthermore, the MYB family members were analyzed from the aspects of protein sequences alignment, evolution, motif prediction, promoter cis-acting element analysis, and gene differential expression under different salt treatments using both a pot experiment and hydroponic experiment. The results showed that the R2R3-MYB genes of C.paliurus conserved functional domains, whereas four R2R3-MYB genes that might respond to salt stress via regulating plant hormone signals were identified in this study. This work provides a basis for further functional characterization of R2R3-MYB TFs in C. paliurus.

R2R3-MYB Transcription Factor PlMYB108 Confers Drought Tolerance in Herbaceous Peony (Paeonia lactiflora Pall.)

The MYB transcription factor (TF) is crucial for plant growth, development, and response to abiotic stress, but it is rarely reported in the herbaceous peony (Paeonia lactiflora Pall.). Here, an MYB TF gene was isolated, and based on our prior mRNA data from P. lactiflora samples, it was treated with drought stress (DS). Its complete cDNA structure was 1314 bp, which encoded 291 amino acids (aa). Furthermore, using sequence alignment analysis, we demonstrated that PlMYB108 was an R2R3-MYB TF. We also revealed that PlMYB108 was primarily localized in the nucleus. Its levels rose during DS, and it was positively correlated with drought tolerance (DT) in P. lactiflora. In addition, when PlMYB108 was overexpressed in tobacco plants, the flavonoid content, antioxidant enzyme activities, and photosynthesis were markedly elevated. Hence, the transgenic plants had stronger DT with a higher leaf water content and lower H2O2 accumulation compared to the wild-type (WT) plants. Based on these results, PlMYB108 is a vital gene that serves to increase flavonoid accumulation, reactive oxygen species (ROS), scavenging capacity, and photosynthesis to confer DT. The results would provide a genetic resource for molecular breeding to enhance plant DT.

AP2/ERF, an important cold stress-related transcription factor family in plants: A review

Increasing the vulnerability of plants especially crops to a wide range of cold stress reduces plant growth, development, yield production, and plant distribution. Cold stress induces physiological, morphological, biochemical, phenotypic, and molecular changes in plants. Transcription factor (TF) is one of the most important regulators that mediate gene expression. TF is activated by the signal transduction pathway, together with cis-acting element modulate the transcription of cold-responsive genes which contribute to increasing cold tolerance in plants. Here, AP2/ERF TF family is one of the most important cold stress-related TF families that along with other TF families, such as WRKY, bHLH, bZIP, MYB, NAC, and C2H2 interrelate to enhance cold stress tolerance. Over the past decade, significant progress has been found to solve the role of transcription factors (TFs) in improving cold tolerance in plants, such as omics analysis. Furthermore, numerous studies have identified and characterized the complexity of cold stress mechanisms among TFs or between TFs and other factors (endogenous and exogenous) including phytohormones, eugenol, and light. The role, function, and relationship among these TFs or between TFs and other factors to enhance cold tolerance still need to be clarified. Here, the current study analysed the role of AP2/ERF TF and the linkages among AP2/ERF with MYB, WRKY, bZIP, bHLH, C2H2, or NAC against cold stress tolerance.

Genome-wide analysis of MYB transcription factors and their responses to salt stress in Casuarina equisetifolia

BACKGROUND

MYB transcription factors are a kind of DNA binding protein that can specifically interact with the promoter region. Members of MYB TFs are widely involved in plant growth and development, secondary metabolism, stress response, and hormone signal transduction. However, there is no report of comprehensive bioinformatics analysis on the MYB family of Casuarina equisetifolia.

RESULTS

In this study, bioinformatics methods were used to screen out 182 MYB transcription factors from the Casuarina equisetifolia genome database, including 69 1R-MYB, 107 R2R3-MYB, 4 R1R2R3-MYB, and 2 4R-MYB. The C. equisetifolia R2R3-MYB genes were divided into 29 groups based on the phylogenetic topology and the classification of the MYB superfamily in Arabidopsis thaliana, while the remaining MYB genes (1R-MYB, R1R2R3-MYB, and 4R-MYB) was divided into 19 groups. Moreover, the conserved motif and gene structure analysis shown that the members of the CeqMYBs were divided into the same subgroups with mostly similar gene structures. In addition, many conserved amino acids in the R2 and R3 domains of CeqMYBs by WebLogo analysis, especially tryptophan residues (W), with 3 conserved W in R2 repeat and 2 conserved W in R3 repeat. Combining promoter and GO annotation analysis, speculated on the various biological functions of CeqMYBs, thus 32 MYB genes were selected to further explore its response to salt stress by using qPCR analysis technique. Most CeqMYB genes were differentially regulated following multiple salt treatments.

CONCLUSIONS

Seven genes (CeqMYB164, CeqMYB4, CeqMYB53, CeqMYB32, CeqMYB114, CeqMYB71 and CeqMYB177) were assigned to the "response to salt stress" by GO annotation. Among them, the expression level of CeqMYB4 was up-regulated under various salt treatments, indicating CeqMYB4 might participated in the response to salt stress. Our results provide important information for the biological function of C. equisetifolia, as well as offer candidate genes for further study of salt stress mechanism.

Systematic analysis of differentially expressed ZmMYB genes related to drought stress in maize

MYB transcription factors play pivotal roles in hormone conduction signaling and abiotic stress response. In this study, 54 differentially expressed ZmMYB genes were identified and comprehensive analyses were conducted including gene's structure, chromosomal localization, phylogenetic tree, motif prediction, cis-elements and expression patterns. The results showed that 54 genes were unevenly distributed on 10 chromosomes and classified into eleven main subgroups by phylogenetic analysis, supported by motif and exon/intron analyses. The mainly stress-related cis-elements were ABRE, ARE, MBS and DRE-core. In addition, 8 core ZmMYB genes were identified by co-expression network. qRT-PCR results showed that the 8 ZmMYB genes exhibited different expression levels under different abiotic stresses, indicating that they were responsive to various abiotic stress. These results will provide insight for further functional investigation of ZmMYB genes.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12298-021-01013-2.

Integrating transcriptome and metabolome analyses of the response to cold stress in pumpkin (Cucurbita maxima)

Cucurbita maxima belong to the genus Cucurbita and are of nutritional and economic importance. Physiological activity, transcriptome, and metabolome analyses of leaf samples from the C. maxima inbreding line IL7 treated at 5 °C and 25 °C were performed. Cold stress resulted in a significant increase in the malondialdehyde content, relative electrical conductivity, soluble protein, sugar content, and catalase activity. A total of 5,553 differentially expressed genes were identified, of which 2,871 were up-regulated and 2,682 down-regulated. In addition, the transcription of differentially expressed genes in the plant hormone signal transduction pathway and transcription factor families of AP2/ERF, bHLH, WRKY, MYB, and HSF was activated. Moreover, 114 differentially expressed metabolites were identified by gas chromatography time-of-flight mass spectrometry, particularly through the analysis of carboxylic acids and derivatives, and organooxygen compounds. The demonstration of a series of potential metabolites and corresponding genes highlighted a comprehensive regulatory mechanism. These findings will provide novel insights into the molecular mechanisms associated with the response to cold stress in C. maxima.