V-myb Avian Myeloblastosis Viral Oncogene Research Articles

Transcriptome analysis reveals the molecular patterns regulating prickle reduction in grafted Zanthoxylum armatum

Grafting has been found to effectively reduce the prickly nature of Zanthoxylum armatum seedlings, but the molecular mechanisms are unclear. A comparative transcriptome analysis was performed on stems (JJ) and leaves (JY) of grafted stems (SJ) and leaves (SY) of non-grafted Zanthoxylum armatum seedlings. The authors obtained 3097, 2124, 5995, and 5043 differentially expressed genes from JJ vs. SJ, JY vs. SY, JY vs. JJ, and SY vs. SJ with 17 co-expressed genes. The RNA-seq results were confirmed by qRT-PCR analysis. Function annotations showed that many DEGs enriched plant hormone signal transduction, phenylpropanoid biosynthesis, and plant-pathogen interaction. Secondary metabolites associated with stress-related hormones and defense were noticeably up-regulated in grafted plants. However, key enzymes regulating lignin synthesis were slightly down-regulated in grafted plants. Additionally, grafted plants had several noticeable up-regulated stress-response TFs (transcription factors), including NAC (NAM, ATAF1/2, CUC1/2), ERF (ethylene response factor), MYB (v-myb avian myeloblastosis viral oncogene homolog), bHLH (basic helix-loop-helix), and WRKY. This study generated abundant sequences for elucidating the genetic differences between grafted and non-grafted Z. armatum.

Key factors for differential drought tolerance in two contrasting wild materials of Artemisia wellbyi identified using comparative transcriptomics

BackgroundDrought is a significant condition that restricts vegetation growth on the Tibetan Plateau. Artemisia wellbyi is a unique semi-shrub-like herb in the family Compositae, which distributed in northern and northwest of Tibetan Plateau. It is a dominant species in the community that can well adapt to virous environment stress, such as drought and low temperature. Therefore, A. wellbyi. has a potential ecological value for soil and water conservation of drought areas. Understanding the molecular mechanisms of A. wellbyi. that defense drought stress can acquire the key genes for drought resistance breeding of A. wellbyi. and provide a theoretical basis for vegetation restoration of desertification area. However, they remain unclear. Thus, our study compared the transcriptomic characteristics of drought-tolerant “11” and drought-sensitive “6” material of A. wellbyi under drought stress.ResultsA total of 4875 upregulated and 4381 downregulated differentially expressed genes (DEGs) were induced by drought in the tolerant material; however, only 1931 upregulated and 4174 downregulated DEGs were induced by drought in the sensitive material. The photosynthesis and transcriptional regulation differed significantly with respect to the DEGs number and expression level. We found that CDPKs (calmodulin-like domain protein kinases), SOS3 (salt overly sensitive3), MAPKs (mitogen-activated protein kinase cascades), RLKs (receptor like kinase), and LRR-RLKs (repeat leucine-rich receptor kinase) were firstly involved in response to drought stress in drought tolerant A. wellbyi. Positive regulation of genes associated with the metabolism of ABA (abscisic acid), ET (ethylene), and IAA (indole acetic acid) could play a crucial role in the interaction with other transcriptional regulatory factors, such as MYBs (v-myb avian myeloblastosis viral oncogene homolog), AP2/EREBPs (APETALA2/ethylene-responsive element binding protein family), WRKYs, and bHLHs (basic helix-loop-helix family members) and receptor kinases, and regulate downstream genes for defense against drought stress. In addition, HSP70 (heat shock protein70) and MYB73 were considered as the hub genes because of their strong association with other DEGs.ConclusionsPositive transcriptional regulation and negative regulation of photosynthesis could be associated with better growth performance under drought stress in the drought-tolerant material. In addition, the degradation of sucrose and starch in the tolerant A. wellbyi to alleviate osmotic stress and balance excess ROS. These results highlight the candidate genes that are involved in enhancing the performance of drought-tolerant A. wellbyi and provide a theoretical basis for improving the performance of drought-resistant A. wellbyi.

The physiological and transcriptomic study of secondary growth in Neolamarckia cadamba stimulated by the ethylene precursor ACC

Though many biological roles of ethylene have been investigated intensively, the molecular mechanism of ethylene's action in woody plants remains unclear. In this study, we investigated the effects of exogenous 1-aminocyclopropane-1-carboxylic acid (ACC), the precursor of ethylene, on the growth of Neolamarckia cadamba seedlings, a fast-growing tropical tree. After 14 days of ACC treatment, the plants showed a reduced physiological morphology while stem diameter increased; however, this did not occur after the addition of 1-MCP. Meanwhile, the lignin content of N. cadamba also increased. Transcriptome analysis revealed that the expression of the ethylene biosynthesis and signaling genes ACC oxidase (ACO) and ethylene insensitive 3 (EIN3) were up-regulated mainly at the 6th hour and the 3rd day of the ACC treatment, respectively. The transcription levels of transcription factors, mainly in the basic helix-loop-helix (bHLH), ethylene response factor (ERF), WRKY and v-myb avian myeloblastosis viral oncogene homolog (MYB) families, involved in the ethylene signaling and secondary growth also increased significantly. Furthermore, in accordance to the increased lignification of the stem, the transcriptional level of key enzymes in the phenylalanine pathway were elevated after the ACC treatment. Our results revealed the physiological and molecular mechanisms underlying the secondary growth stimulated by exogenous ACC treatment on N. cadamba seedlings.

IbMYB308, a Sweet Potato R2R3-MYB Gene, Improves Salt Stress Tolerance in Transgenic Tobacco

The MYB (v-myb avian myeloblastosis viral oncogene homolog) transcription factor family plays an important role in plant growth, development, and response to biotic and abiotic stresses. However, the gene functions of MYB transcription factors in sweet potato (Ipomoea batatas (L.) Lam) have not been elucidated. In this study, an MYB transcription factor gene, IbMYB308, was identified and isolated from sweet potato. Multiple sequence alignment showed that IbMYB308 is a typical R2R3-MYB transcription factor. Further, quantitative real-time PCR (qRT-PCR) analysis revealed that IbMYB308 was expressed in root, stem, and, especially, leaf tissues. Moreover, it showed that IbMYB308 had a tissue-specific profile. The experiment also showed that the expression of IbMYB308 was induced by different abiotic stresses (20% PEG-6000, 200 mM NaCl, and 20% H2O2). After a 200 mM NaCl treatment, the expression of several stress-related genes (SOD, POD, APX, and P5CS) was upregulation in transgenic plants, and the CAT activity, POD activity, proline content, and protein content in transgenic tobacco had increased, while MDA content had decreased. In conclusion, this study demonstrated that IbMYB308 could improve salt stress tolerance in transgenic tobacco. These findings lay a foundation for future studies on the R2R3-MYB gene family of sweet potato and suggest that IbMYB308 could potentially be used as an important positive factor in transgenic plant breeding to improve salt stress tolerance in sweet potato plants.

Transcriptome Level Analysis of Genes of Exogenous Ethylene Applied under Phosphorus Stress in Chinese Fir.

Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) is a widely grown gymnosperm in China. Phosphorus (P) is an indispensable nutrient for the growth of Chinese fir. Inorganic phosphate (Pi) deficiency exists in soils of many Chinese fir planting area regions, and the trees themselves have limited efficiency in utilizing P from the soil. Ethylene is important in regulation responses to nutrient deficiencies. However, little is known about how ethylene signals participate in Pi stress in Chinese fir. A total of six different treatments were performed to reveal the transcript levels of Chinese fir under Pi, ethephon (an ethylene-releasing compound), and CoCl2 (cobalt chloride, an ethylene biosynthesis inhibitor) treatments. We assembled a full-length reference transcriptome containing 22,243 unigenes as a reference for UMI RNA-seq (Digital RNA-seq). There were 586 Differentially Expressed Genes (DEGs) in the Pi starvation (NP) group, while DEGs from additional ethephon or CoCl2 in NP were 708 and 292, respectively. Among the DEGs in each treatment, there were 83 TFs in these treatment groups. MYB (v-myb avian myeloblastosis viral oncogene homolog) family was the most abundant transcription factors (TFs). Three ERF (Ethylene response factor) family genes were identified when only ethylene content was imposed as a variable. Enrichment analysis indicated that the ascorbate and aldarate metabolism pathway plays a key role in resistance to Pi deficiency. This study provides insights for further elucidating the regulatory mechanism of Pi deficiency in Chinese fir.

Population diversity analyses provide insights into key horticultural traits of Chinese native thymes.

Chinese native thymes (CNTs) in the genus Thymus (family Lamiaceae) are rich in bioactive terpenes, which exert antiviral, anti-inflammatory, antioxidation, immunological, and antimicrobial effects. Plants exhibit morphological variation, including erect-type and creeping-type growth forms; however, the molecular mechanisms underlying important horticultural traits have not been determined. Here, we collected 39 CNTs providing strategic plant resources for studies of lignin, terpenoids, and glandular trichomes of thymes. Using resequencing data as well as phenotypic, metabonomic, phylogenetic, population genetic, and transcriptomic analyses, we identified and characterized key genes involved in lignin biosynthesis, terpenoid biosynthesis, and glandular trichome formation. We found many regulatory genes or transcription factors related to these three important horticultural traits, including genes encoding caffeic acid O-methyltransferase (COMT), terpene synthase (TPS), v-myb avian myeloblastosis viral oncogene homolog (MYB), and homeodomain-leucine zipper (HD-ZIP). Population diversity analyses provided insights into growth form, terpenoid, and glandular trichome evolution in CNTs. Furthermore, our results revealed that T. mongolicus accessions might be wild ancestors, and T. quinquecostatus, T. quinquecostatus var. asiaticus, and T. quinquecostatus var. przewalskii might be transitional accessions that derived from T. mongolicus accessions. Finally, T. nervulosus, T. inaequalis, T. mandschuricus, T. curtus, T. amurensis, T. proximus, T. altaicus, T. roseus, and T. marschallianus showed high divergence. We found evidence for introgression between erect-type European cultivated thymes and CNTs. These findings improve our understanding of the determinants of variation in horticultural traits and provide candidate loci for research and breeding.

VvMYB1 potentially affects VvTOR gene expression by regulating VvTOR promoter and participates in glucose accumulation

MYB (v-myb avian myeloblastosis viral oncogene homolog) transcription factors make up one of the largest protein families in plants. The TOR (target of rapamycin) signaling network plays a pivotal role in sugar metabolism and plant growth. In this article, we utilized grape (Vitis vinifera) calli to explore the relationship between VvMYB1 and VvTOR. By using yeast one-hybrid and dual-luciferase reporter system, we speculated that there may be other proteins that help VvMYB1 and VvTOR promoter bond in grape calli, and the interaction action sites were located between the VvTOR 400-bp promoter fragment and the 1200-bp promoter fragment. The subcellular localization results suggest that VvMYB1 is found in the nucleus. Moreover, the expression level of VvTOR increased in the transgenic calli with overexpression of VvMYB1. These findings provide further evidence that VvMYB1 regulates VvTOR expression. We also found that overexpression of VvMYB1 increased glucose accumulation and affected expression of sugar-related genes. Our results suggest that there is a crosstalk between VvMYB1, VvTOR, and glucose accumulation.

Overexpression of a Malus baccata MYB Transcription Factor Gene MbMYB4 Increases Cold and Drought Tolerance in Arabidopsis thaliana.

In the natural environment, plants often face unfavorable factors such as drought, cold, and freezing, which affect their growth and yield. The MYB (v-myb avian myeloblastosis viral oncogene homolog) transcription factor family is widely involved in plant responses to biotic and abiotic stresses. In this study, Malus baccata (L.) Borkh was used as the research material, and a gene MbMYB4 of the MYB family was cloned from it. The open reading frame (ORF) of MbMYB4 was found to be 762 bp, encoding 253 amino acids; sequence alignment results and predictions of the protein structure indicated that the MbMYB4 protein contained the conserved MYB domain. Subcellular localization showed that MbMYB4 was localized in the nucleus. In addition, the use of quantitative real-time PCR (qPCR) technology found that the expression of MbMYB4 was enriched in the young leaf and root, and it was highly affected by cold and drought treatments in M. baccata seedlings. When MbMYB4 was introduced into Arabidopsis thaliana, it greatly increased the cold and drought tolerance in the transgenic plant. Under cold and drought stresses, the proline and chlorophyll content, and peroxidase (POD) and catalase (CAT) activities of transgenic A. thaliana increased significantly, and the content of malondialdehyde (MDA) and the relative conductivity decreased significantly, indicating that the plasma membrane damage of transgenic A. thaliana was lesser. Therefore, the overexpression of the MbMYB4 gene in A. thaliana can enhance the tolerance of transgenic plants to cold and drought stresses.

The R2R3-MYB transcription factor MYB44 modulates carotenoid biosynthesis in Ulva prolifera

Carotenoids compose a large group of natural terpenoid pigments and are widely distributed in algae. Carotenoids play key roles in many biological processes in Ulva prolifera, and the carotenoid biosynthetic pathway has been thoroughly elucidated; however, the mechanisms through which carotenoid biosynthesis is regulated by transcription factors are not fully understood, especially in algae. In this study, we reported that the R2R3-MYB transcription factor UpMYB44 is a positive regulator of carotenoid biosynthesis in U. prolifera. The full-length coding DNA sequence of UpMYB44 is 1437 bp and encodes a putative 478-amino acid protein. The UpMYB44 protein is located in the nucleus in U. prolifera and has transcriptional activity. UpMYB44 can regulate carotenoid accumulation by directly interacting with the key carotenoid synthesis gene UpPDS and can enhance activity under some environmental stresses, including temperature, light and salinity stresses, resulting in an increase in total carotenoids, β-carotene and lutein. Using yeast one-hybrid assays and electrophoretic mobility shift assays, we demonstrated that UpMYB44 directly binds to the cis-elements of the promoter of UpPDS. The results indicated that the expression level of the key gene involved in carotenoid biosynthesis affected the biosynthesis of carotenoids in U. prolifera at the molecular level and was regulated by UpMYB44. Overall, we characterized the U. prolifera transcription factor UpMYB44, which was found to activate expression of the key gene that plays an important role in the carotenoid biosynthetic pathway in U. prolifera. The data presented in this study suggest a role of UpMYB44 in carotenoid metabolism exerted by transcriptional activation of carotenoid biosynthetic pathway genes. These results further support recent progress in elucidating the roles of v-myb avian myeloblastosis viral oncogene homolog transcription factors in carotenoid regulation in algae.

Meta-Analysis of the Effect of Overexpression of MYB Transcription Factors on the Regulatory Mechanisms of Anthocyanin Biosynthesis.

MYBs (v-myb avian myeloblastosis viral oncogene homologs) are important transcriptional regulators that play critical roles in the regulation of anthocyanin biosynthesis. The overexpression of MYB genes has been reported in different plant species. However, the inconsistent strategies to assess transgenic plants have made it difficult to explain the complex mechanisms of regulation of anthocyanin biosynthesis by MYBs. We report here a meta-analysis of 608 studies from 206 publications assessing the effects of MYB overexpression on anthocyanins and evaluate the experimental variables that have an influence on transgenic plant performance. We found that MYB expression enhanced the magnitude of 20 out of 26 examined plant parameters by at least of 21% and reduced the magnitude of 1 indicator by at least 37%. We explored the variety of moderating variables causing these variations. A deeper color induced by MYBs caused higher plant attributes as compared to normal color changes. MYB genes from dicots stimulated the accumulation of anthocyanins, flavonols and impacted the expressions of PAL, CHS, CHI, FLS, F3′5′H, ANS, UFGT, and ANR as compared to monocots. Heterologous expression and homologous expression showed a great difference in anthocyanin biosynthesis. Transient gene transformation had a significant effect on the expression of flavonoid biosynthetic genes, and stable transformation had a significant effect on flavonoid accumulation. Stress could result in a significantly increased accumulation of flavonoids, especially anthocyanin, flavonol, and proanthocyanidin. Our study, thus, provides new insights into the function of MYBs in the regulatory mechanisms of flavonoid biosynthesis and the use of genetic engineering for improving anthocyanins contents.

Integrated transcriptomics and metabolomics uncover the molecular basis of flavonoid accumulation in the rhizomes of two Cymbidium tortisepalum var. longibracteatum cultivars

The rhizome is crucial for asexual propagation in plants. Green rhizome (termed as GR) and yellow rhizome (termed as YR) are the rhizomes of two Cymbidium tortisepalum var. longibracteatum cultivars with colour differences. In this study, we carried out integrated transcriptomic and metabolomic profiling to explore the pathways and key genes between them. The transcriptome assembled 134,527 unigenes and 508 unigenes (244 upregulated and 264 downregulated) with differential expression patterns. Metabolomic analysis identified 420 metabolites, and 115 were differentially accumulated metabolites, including 37 upregulated and 78 downregulated metabolites. Integration of transcriptome profiling and metabolite analysis revealed "phenylpropanoid biosynthesis" and "flavonoid biosynthesis" were significantly enriched. One R2R3 type v-myb avian myeloblastosis viral oncogene homologue (R2R3-MYB) transcription factor (c1121_g1), two basic helix-loop-helix (bHLH) transcription factors (c59082_g2 and c103838_g1), and five flavonoid biosynthesis related unigenes (c34902_g1, c82361_g1, c22242_g1, c39937_g1, c47509_g1) were highly expressed in YR, which is consistent with the flavonoid content. These findings shed light on the regulation of flavonoid biosynthesis and will contribute to the breeding of new cultivars in orchids.

AtMYB12-Expressing Transgenic Tobacco Increases Resistance to Several Phytopathogens and Aphids

Phytopathogens and pests are two major factors that limit the growth of plants. The expression of a flavonoid regulator gene, AtMYB12(AT2G47460), has been reported to increase the endogenous flavonoid content of tobacco and tomato. Previous research has only focused on the regulation mechanism of v-myb avian myeloblastosis viral oncogene homolog (MYB) transcription factors under single stress conditions. Here, research showed that AtMYB12 was involved in regulating the resistance of tobacco to multiple biological stresses such as phytopathogens and aphid. We reported that transgenic tobacco carrying AtMYB12 was more resistant to Ralstonia solanacearum when the up-regulated expression of several defense-related markers, such as NbPR1a, NbNOA1, and NbrbohB, was activated, suggesting that the priming defense of a plant may contribute to bacterial disease resistance. The improvement of the resistance of AtMYB12-expressing transgenic tobacco is achieved by promoting the production of ROS, H2O2, and NO. AtMYB12-expressing transgenic tobacco also has resistance to fungal pathogens, such as Colletotrichum nicotianae Averna and Alternaria alternate. The enrichment of flavonols components, such as rutin, which directly inhibit the growth of C. nicotianae and A. alternate, may also contribute to the defense mediated by AtMYB12 over-expression. At the same time, the results also confirm that AtMYB12-expressing transgenic tobacco enhanced plant resistance to aphid-infested (Aphidoidea) pests. These results suggest that the AtMYB12 gene is a good candidate for pest and disease control, with limited resistance costs and enrichment in flavonols, and that AtMYB12 has a potential in the breeding of disease-resistant tobacco crops.

MYBL2 in synergy with CDC20 promotes the proliferation and inhibits apoptosis of gastric cancer cells.

Gastric cancer (GC) is a common malignant tumor with a high morbidity and mortality worldwide. It has been reported that V-Myb avian myeloblastosis viral oncogene homolog-like 2 (MYBL2) could be a promising prognostic biomarker for GC. However, the specific role of MYBL2 in GC progression remains unclear. To examine the role of MYBL2 in GC progression and investigate the underlying mechanisms. The mRNA levels of target genes were detected using quantitative real-time polymerase chain reaction (RT-qPCR) and protein expression was measured with western blot analysis. Cell Counting Kit-8 (CCK-8) and colony formation assays were employed to inspect HGC-27 cell proliferation, and cellular apoptosis was determined with TUNEL staining. Finally, the interaction of MYBL2 and cell division cycle 20 (CDC20) was verified with immunoprecipitation. MYBL2 was confirmed to be overexpressed in GC cells. MYBL2 knockdown inhibited HGC-27 cell proliferation and promoted cellular apoptosis, and these effects were reversed by CDC20 overexpression. Interestingly, MYBL2 interacted with CDC20 and regulated its expression. MYBL2 knockdown also inhibited activation of the Wnt/β-catenin signaling pathway, while CDC20 overexpression showed the opposite effect. In summary, the synergy between MYBL2 and CDC20 induced the proliferation of GC cells and inhibited cell apoptosis; these effects may have involved the Wnt/β-catenin signaling pathway. Thus, MYBL2 may be a promising target for GC treatment.

Identification of microRNAs and their target genes related to needle discoloration of evergreen tree Chinese cedar (Cryptomeria fortunei) in cold winters.

Comparative analysis of miRNAs and their gene targets between the evergreen and yellowish-brown Cryptomeria fortunei phenotypes in cold winters suggests a possible role of miRNA-regulated pathways in needle color. Cryptomeria fortunei (Chinese cedar) is a conifer tree of considerable economic, ornamental and ecological importance. Despite the evergreen nature of C. fortunei, most needles turn yellowish- or reddish-brown in winter. The roles of microRNAs (miRNAs) in regulating pigment biosynthesis in color-leafed plants have been widely investigated. However, whether or not an miRNA-mediated staged discoloration mechanism exists in evergreen C. fortunei is currently unknown. In this study, we deciphered the microRNAs landscape in overwintering C. fortunei needles using high-throughput sequencing. A total of 517 known and 212 novel miRNA mature/star sequences, including 233 differentially expressed miRNAs, were identified. Based on integrated transcriptome and miRNA analysis, 2702 target unigenes of the miRNAs were predicted and these targets were significantly enriched in pigment-related biosynthesis pathways. A miRNA-target pigment biosynthesis regulatory network was then constructed, and its module miRNA (ath-miR858b, aly-miR858-3p, cme-miR828 and novel33_mature)-MYBs (v-myb avian myeloblastosis viral oncogene homolog) appeared to be a key factor regulating needle discoloration in C. fortunei. These miRNA-MYBs were further confirmed by degradome sequencing. Overall, these findings provide new insight into the posttranscriptional regulatory mechanism of leaf/needle discoloration in gymnosperms and may contribute to the miRNA-mediated genetic improvement of evergreen C. fortunei needles.

Sulfoquinovosyl diacylglycerol synthase 1 impairs glycolipid accumulation and photosynthesis in phosphate-deprived rice

Phosphate (Pi)-starved crops utilize phospholipids as a source for internal Pi supply by replacing non-phosphorus glycolipids. In rice, sulfoquinovosyl diacylglycerol synthase 1 (OsSQD1) functions as a key enzyme in the first step to catalyze sulfoquinovosyldiacylglycerol (SQDG) formation. Here we study differential expression of OsSQD1 in response to Pi, nitrogen, potassium, and iron-deficiencies in rice. Electrophoretic mobility shift assay suggested that OsSQD1 is regulated by OsPHR2 (Phosphate Starvation Response2), a MYB (v-myb avian myeloblastosis viral oncogene homolog) domain-containing transcription factor. The concentrations of different lipid species in ossqd1 knockout mutant demonstrated that OsSQD1 silencing increased the phospholipid content and altered fatty acid composition under Pi-deficiency. Moreover, OsSQD1 silencing reduces glycolipid accumulation under Pi-deficiency, and triggered the saturation of fatty acids in phospholipids and glycolipids treated with different Pi regimes. Relative amounts of transcripts related to phospholipid degradation and glycolipid synthesis were assessed to explore the mechanism by which OsSQD1 exerts an effect on lipid homeostasis under P-deficiency. Furthermore, OsSQD1 silencing inhibited photosynthesis, especially under Pi-deficient conditions, by down-regulating glycolipids in rice shoots. Taken together, our study reveals that OsSQD1 plays a key role in lipid homeostasis, especially glycolipid accumulation under Pi-deficiency, which results in the inhibition of photosynthesis.

Systematic analysis of MYB gene family in Acer rubrum and functional characterization of ArMYB89 in regulating anthocyanin biosynthesis.

The v-myb avian myeloblastosis viral oncogene homolog (MYB) family of transcription factors is extensively distributed across the plant kingdom. However, the functional significance of red maple (Acer rubrum) MYB transcription factors remains unclear. Our research identified 393 MYB transcription factors in the Acer rubrum genome, and these ArMYB members were unevenly distributed across 34 chromosomes. Among them, R2R3 was the primary MYB sub-class, which was further divided into 21 sub-groups with their Arabidopsis homologs. The evolution of the ArMYB family was also investigated, with the results revealing several R2R3-MYB sub-groups with expanded membership in woody species. Here, we report on the isolation and characterization of ArMYB89 in red maple. Quantitative real-time PCR analysis revealed that ArMYB89 expression was significantly up-regulated in red leaves in contrast to green leaves. Sub-cellular localization experiments indicated that ArMYB89 was localized in the nucleus. Further experiments revealed that ArMYB89 could interact with ArSGT1 in vitro and in vivo. Overexpression of ArMYB89 in tobacco enhances the anthocyanin content of transgenic plants. In conclusion, our results contribute to the elucidation of a theoretical basis for the ArMYB gene family, and provide a foundation for further characterization of the biological roles of MYB genes in the regulation of Acer rubrum leaf color.

MYB Transcription Factors and Its Regulation in Secondary Cell Wall Formation and Lignin Biosynthesis during Xylem Development.

The secondary wall is the main part of wood and is composed of cellulose, xylan, lignin, and small amounts of structural proteins and enzymes. Lignin molecules can interact directly or indirectly with cellulose, xylan and other polysaccharide molecules in the cell wall, increasing the mechanical strength and hydrophobicity of plant cells and tissues and facilitating the long-distance transportation of water in plants. MYBs (v-myb avian myeloblastosis viral oncogene homolog) belong to one of the largest superfamilies of transcription factors, the members of which regulate secondary cell-wall formation by promoting/inhibiting the biosynthesis of lignin, cellulose, and xylan. Among them, MYB46 and MYB83, which comprise the second layer of the main switch of secondary cell-wall biosynthesis, coordinate upstream and downstream secondary wall synthesis-related transcription factors. In addition, MYB transcription factors other than MYB46/83, as well as noncoding RNAs, hormones, and other factors, interact with one another to regulate the biosynthesis of the secondary wall. Here, we discuss the biosynthesis of secondary wall, classification and functions of MYB transcription factors and their regulation of lignin polymerization and secondary cell-wall formation during wood formation.

MYB-Mediated Regulation of Anthocyanin Biosynthesis.

Anthocyanins are natural water-soluble pigments that are important in plants because they endow a variety of colors to vegetative tissues and reproductive plant organs, mainly ranging from red to purple and blue. The colors regulated by anthocyanins give plants different visual effects through different biosynthetic pathways that provide pigmentation for flowers, fruits and seeds to attract pollinators and seed dispersers. The biosynthesis of anthocyanins is genetically determined by structural and regulatory genes. MYB (v-myb avian myeloblastosis viral oncogene homolog) proteins are important transcriptional regulators that play important roles in the regulation of plant secondary metabolism. MYB transcription factors (TFs) occupy a dominant position in the regulatory network of anthocyanin biosynthesis. The TF conserved binding motifs can be combined with other TFs to regulate the enrichment and sedimentation of anthocyanins. In this study, the regulation of anthocyanin biosynthetic mechanisms of MYB-TFs are discussed. The role of the environment in the control of the anthocyanin biosynthesis network is summarized, the complex formation of anthocyanins and the mechanism of environment-induced anthocyanin synthesis are analyzed. Some prospects for MYB-TF to modulate the comprehensive regulation of anthocyanins are put forward, to provide a more relevant basis for further research in this field, and to guide the directed genetic modification of anthocyanins for the improvement of crops for food quality, nutrition and human health.

The BpMYB4 Transcription Factor From Betula platyphylla Contributes Toward Abiotic Stress Resistance and Secondary Cell Wall Biosynthesis.

The MYB (v-myb avian myeloblastosis viral oncogene homolog) family is one of the largest transcription factor families in plants, and is widely involved in the regulation of plant metabolism. In this study, we show that a MYB4 transcription factor, BpMYB4, identified from birch (Betula platyphylla Suk.) and homologous to EgMYB1 from Eucalyptus robusta Smith and ZmMYB31 from Zea mays L. is involved in secondary cell wall synthesis. The expression level of BpMYB4 was higher in flowers relative to other tissues, and was induced by artificial bending and gravitational stimuli in developing xylem tissues. The expression of this gene was not enriched in the developing xylem during the active season, and showed higher transcript levels in xylem tissues around sprouting and near the dormant period. BpMYB4 also was induced express by abiotic stress. Functional analysis indicated that expression of BpMYB4 in transgenic Arabidopsis (Arabidopsis thaliana) plants could promote the growth of stems, and result in increased number of inflorescence stems and shoots. Anatomical observation of stem sections showed lower lignin deposition, and a chemical contents test also demonstrated increased cellulose and decreased lignin content in the transgenic plants. In addition, treatment with 100 mM NaCl and 200 mM mannitol resulted in the germination rate of the over-expressed lines being higher than that of the wild-type seeds. The proline content in transgenic plants was higher than that in WT, but MDA content was lower than that in WT. Further investigation in birch using transient transformation techniques indicated that overexpression of BpMYB4 could scavenge hydrogen peroxide and O2.– and reduce cell damage, compared with the wild-type plants. Therefore, we believe that BpMYB4 promotes stem development and cellulose biosynthesis as an inhibitor of lignin biosynthesis, and has a function in abiotic stress resistance.

The MYB transcription factor Baymax1 plays a critical role in rice male fertility.

Key message Rice male fertility gene Baymax1, isolated through map-based cloning, encodes a MYB transcription factor and is essential for rice tapetum and microspore development.Abstract The mining and characterization of male fertility gene will provide theoretical and material basis for future rice production. In Arabidopsis, the development of male organ (namely anther), usually involves the coordination between MYB (v-myb avian myeloblastosis viral oncogene homolog) and bHLH (basic helix-loop-helix) members. However, the role of MYB proteins in rice anther development remains poorly understood. In this study, we isolated and characterized a male sterile mutant (with normal vegetative growth) of Baymax1 (BM1), which encodes a MYB protein. The bm1 mutant exhibited slightly lagging meiosis, aborted transition of the tapetum to a secretory type, premature tapetal degeneration, and abnormal pollen exine formation, leading to ultimately lacks of visible pollens in the mature white anthers. Map-based cloning, complementation and targeted mutagenesis using CRISPR/Cas9 technology demonstrated that the mutated LOC_Os04g39470 is the causal gene in bm1. BM1 is preferentially expressed in rice anthers from stage 5 to stage 10. Phylogenetic analysis indicated that rice BM1 and its homologs in millet, maize, rape, cabbage, and pigeonpea are evolutionarily conserved. BM1 can physically interacts with bHLH protein TIP2, EAT1, and PHD (plant homeodomain)-finger member TIP3, respectively. Moreover, BM1 affects the expression of several known genes related to tapetum and microspore development. Collectively, our results suggest that BM1 is one of key regulators for rice male fertility and may serve as a potential target for rice male-sterile line breeding and hybrid seed production.