Myeloblastosis Research Articles

Genome-wide identification and expression analysis of MYB gene family under nitrogen stress in Panax notoginseng.

The myeloblastosis (MYB) gene family, involved in regulating many important physiological and biochemical processes, is one of the largest transcript factor superfamilies in plants. Since the identification of genome sequencing of Panax notoginseng has been completed, there was little known about the whole genome of its specific MYB gene family and the response to abiotic stresses, in consideration of the excessive application of nitrogen fertilizers in P. notoginseng. In this study, 123 PnMYB genes (MYB genes of P. notoginseng) have been identified and divided into 3 subfamilies by the phylogenetic analysis. These PnMYB genes were unevenly located on 12 chromosomes. Meanwhile, the gene structure and protein conserved domain were established by MEME Suite. The analysis of collinear relationships reflected that there were 121 homologous genes between P. notoginseng and Arabidopsis and 30 between P. notoginseng and rice. Moreover, cis-acting elements of PnMYB gene promoters were predicted which indicated that PnMYBs are involved in biotic, abiotic stress, and hormone induction. The expressions of PnMYB transcription factors in its roots, flowers, and leaves were detected by qRT-PCR and they had tissue-specific expressions and related to the growth of different tissues. Under nitrogen stress, MYB transcription factors had great feedback. Ten R2R3-MYB subfamily genes were significantly induced and indicated the possible function of protecting P. notoginseng from excess nitrogen. With further knowledge on identification of PnMYB gene related to tissue selectivity and abiotic stresses, this study laid the foundation for the functional development of PnMYB gene family and improved the cultivation of P. notoginseng.

A conserved MYB transcription factor is involved in regulating lipid metabolic pathways for oil biosynthesis in green algae.

Green algae can accumulate high levels of triacylglycerol (TAG), yet knowledge remains fragmented on the regulation of lipid metabolic pathways by transcription factors (TFs). Here, via bioinformatics and in vitro and in vivo analyses, we revealed the roles of a myeloblastosis (MYB) TF in regulating TAG accumulation in green algae. CzMYB1, an R2R3-MYB from Chromochloris zofingiensis, was transcriptionally upregulated upon TAG-inducing conditions and correlated well with many genes involved in the de novo fatty acid synthesis, fatty acid activation and desaturation, membrane lipid turnover, and TAG assembly. Most promoters of these genes were transactivated by CzMYB1 in the yeast one-hybrid assay and contained the binding elements CNGTTA that were recognized by CzMYB1 through the electrophoretic mobility shift assay. CrMYB1, a close homologue of CzMYB1 from Chlamydomonas reinhardtii that recognized similar elements for binding, also transcriptionally correlated with many lipid metabolic genes. Insertional disruption of CrMYB1 severely suppressed the transcriptional expression of CrMYB1, as well as of key lipogenic genes, and impaired TAG level considerably under stress conditions. Our results reveal that this MYB, conserved in green algae, is involved in regulating global lipid metabolic pathways for TAG biosynthesis and accumulation.

Kiwifruit MYBS1-like and GBF3 transcription factors influence l-ascorbic acid biosynthesis by activating transcription of GDP-L-galactose phosphorylase 3.

Summary Plant‐derived Vitamin C (l‐ascorbic acid (AsA)) is crucial for human health and wellbeing and thus increasing AsA content is of interest to plant breeders. In plants GDP‐l‐galactose phosphorylase (GGP) is a key biosynthetic control step and here evidence is presented for two new transcriptional activators of GGP.AsA measurement, transcriptomics, transient expression, hormone application, gene editing, yeast 1/2‐hybrid, and electromobility shift assay (EMSA) methods were used to identify two positively regulating transcription factors. AceGGP3 was identified as the most highly expressed GGP in Actinidia eriantha fruit, which has high fruit AsA. A gene encoding a 1R‐subtype myeloblastosis (MYB) protein, AceMYBS1, was found to bind the AceGGP3 promoter and activate its expression. Overexpression and gene‐editing show AceMYBS1 effectively increases AsA accumulation. The bZIP transcription factor AceGBF3 (a G‐box binding factor), also was shown to increase AsA content, and was confirmed to interact with AceMYBS1. Co‐expression experiments showed that AceMYBS1 and AceGBF3 additively promoted AceGGP3 expression. Furthermore, AceMYBS1, but not GBF3, was repressed by abscisic acid, resulting in reduced AceGGP3 expression and accumulation of AsA.This study sheds new light on the roles of MYBS1 homologues and ABA in modulating AsA synthesis, and adds to the understanding of mechanisms underlying AsA accumulation.

Genome-Wide Expression and Physiological Profiling of Pearl Millet Genotype Reveal the Biological Pathways and Various Gene Clusters Underlying Salt Resistance.

Pearl millet (Pennisetum glaucum L.) is a vital staple food and an important cereal crop used as food, feed, and forage. It can withstand heat and drought due to the presence of some unique genes; however, the mechanism of salt stress has been missing in pearl millet until now. Therefore, we conducted a comparative transcriptome profiling to reveal the differentially expressed transcripts (DETs) associated with salt stress in pearl millet at different time points, such as 1, 3, and 7 h, of salt treatment. The physiological results suggested that salt stress significantly increased proline, malondialdehyde (MDA) content, and hydrogen peroxide (H2O2) in pearl millet at 1, 3, and 7 h of salt treatment. In addition, pearl millet plants regulated the activities of superoxide dismutase, catalase, and peroxidase to lessen the impact of salinity. The transcriptomic results depicted that salt stress upregulated and downregulated the expression of various transcripts involved in different metabolic functions. At 1 and 7 h of salt treatment, most of the transcripts were highly upregulated as compared to the 3 h treatment. Moreover, among commonly enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, the mitogen-activated protein kinase (MAPK) signaling pathway and peroxisome pathway were significantly enriched. The DETs related to hormone signaling (auxins, ethylene, gibberellin, and abscisic acid), kinases, protein modifications, and degradation were also identified, depicting the possible role of hormones and kinases to enhance plant tolerance against salt stress. Furthermore, the transcription factors, such as ethylene-responsive element binding factors (ERF), basic helix-loop-helix (bHLH), HMG box-containing protein (HBP), MADS, myeloblastosis (MYB), and WRKY, were predicted to significantly regulate different transcripts involved in salt stress responses at three different time points. Overall, this study will provide new insights to better understand the salt stress regulation mechanisms in pearl millet to improve its resistance against salinity and to identify new transcripts that control these mechanisms in other cereals.

Hydrogen sulphide (H2 S) in the hidden half: Role in root growth, stress signalling and rhizospheric interactions.

Apart from nitric oxide (NO) and carbon monoxide (CO), hydrogen sulphide (H2 S) has emerged as a potential gasotransmitter that has regulatory roles in root differentiation, proliferation and stress signalling. H2 S metabolism in plants exhibits spatio-temporal differences that are intimately associated with sulphide signalling in the cytosol and other subcellular components, e.g. chloroplast and mitochondria. H2 S biosynthesis in plant organs uses both enzymatic and non-enzymatic pathways. H2 S generation in roots and aerial organs is modulated by developmental phase and changes in environmental stimuli. H2 S has an influential role in root development and in the nodulation process. Studies have revealed that H2 S is a part of the auxin and NO signalling pathways in roots, which induce lateral root formation. At the molecular level, exogenous application of H2 S regulates expression of several transcription factors, viz. LBD (Lateral organ Boundaries Domain), MYB (myeloblastosis) and AP2/ERF (Apetala 2/ Ethylene Response Factor), which stimulate upregulation of PpLBD16 (Lateral organ boundaries domain 16), thereby significantly increasing the number of lateral roots. Concomitantly, H2 S acts as a crucial signalling molecule in roots during various abiotic stresses, e.g. drought, salinity heavy metals (HMs), etc., and augments stress tolerance in plants. Interestingly, extensive crosstalk exists between H2 S, NO, ABA, calcium and ethylene during stress, which escalate plant defence and regulate plant growth and productivity. Hence, the present review will elaborate the role of H2 S in root development, stress alleviation, legume-Rhizobium symbiosis and rhizosphere signalling. The review also examines the mechanism of H2 S-mediated abiotic stress mitigation and cross-talk with other signaling molecules.

Comprehensive analysis of 1R- and 2R-MYBs reveals novel genic and protein features, complex organisation, selective expansion and insights into evolutionary tendencies.

Myeloblastosis (MYB) family, the largest plant transcription factor family, has been subcategorised based on the number and type of repeats in the MYB domain. In spite of several reports, evolution of MYB genes and repeats remains enigmatic. Brassicaceae members are endowed with complex genomes, including dysploidy because of its unique history with multiple rounds of polyploidisation, genomic fractionations and rearrangements. The present study is an attempt to gain insights into the complexities of MYB family diversity, understand impacts of genome evolution on gene families and develop an evolutionary framework to understand the origin of various subcategories of MYB gene family. We identified and analysed 1129 MYBs that included 1R-, 2R-, 3R- and atypical-MYBs across sixteen species representing protists, fungi, animals and plants and exclude MYB identified from Brassicaceae except Arabidopsis thaliana; in addition, a total of 1137 2R-MYB genes from six Brassicaceae species were also analysed. Comparative analysis revealed predominance of 1R-MYBs in protists, fungi, animals and lower plants. Phylogenetic reconstruction and analysis of selection pressure suggested ancestral nature of R1-type repeat containing 1R-MYBs that might have undergone intragenic duplication to form multi-repeat MYBs. Distinct differences in gene structure between 1R-MYB and 2R-MYBs were observed regarding intron number, the ratio of gene length to coding DNA sequence (CDS) length and the length of exons encoding the MYB domain. Conserved as well as novel and lineage-specific intron phases were identified. Analyses of physicochemical properties revealed drastic differences indicating functional diversification in MYBs. Phylogenetic reconstruction of 1R- and 2R-MYB genes revealed a shared structure-function relationship in clades which was supported when transcriptome data was analysed in silico. Comparative genomics to study distribution pattern and mapping of 2R-MYBs revealed congruency and greater degree of synteny and collinearity among closely related species. Micro-synteny analysis of genomic segments revealed high conservation of genes that are immediately flanking the surrounding tandemly organised 2R-MYBs along with instances of local duplication, reorganisations and genome fractionation. In summary, polyploidy, dysploidy, reshuffling and genome fractionation were found to cause loss or gain of 2R-MYB genes. The findings need to be supported with functional validation to understand gene structure-function relationship along the evolutionary lineage and adaptive strategies based on comparative functional genomics in plants.

Newly Developed MAGIC Population Allows Identification of Strong Associations and Candidate Genes for Anthocyanin Pigmentation in Eggplant.

Multi-parent advanced generation inter-cross (MAGIC) populations facilitate the genetic dissection of complex quantitative traits in plants and are valuable breeding materials. We report the development of the first eggplant MAGIC population (S3 Magic EGGplant InCanum, S3MEGGIC; 8-way), constituted by the 420 S3 individuals developed from the intercrossing of seven cultivated eggplant (Solanum melongena) and one wild relative (S. incanum) parents. The S3MEGGIC recombinant population was genotyped with the eggplant 5k probes SPET platform and phenotyped for anthocyanin presence in vegetative plant tissues (PA) and fruit epidermis (FA), and for the light-insensitive anthocyanic pigmentation under the calyx (PUC). The 7,724 filtered high-confidence single-nucleotide polymorphisms (SNPs) confirmed a low residual heterozygosity (6.87%), a lack of genetic structure in the S3MEGGIC population, and no differentiation among subpopulations carrying a cultivated or wild cytoplasm. Inference of haplotype blocks of the nuclear genome revealed an unbalanced representation of the founder genomes, suggesting a cryptic selection in favour or against specific parental genomes. Genome-wide association study (GWAS) analysis for PA, FA, and PUC detected strong associations with two myeloblastosis (MYB) genes similar to MYB113 involved in the anthocyanin biosynthesis pathway, and with a COP1 gene which encodes for a photo-regulatory protein and may be responsible for the PUC trait. Evidence was found of a duplication of an ancestral MYB113 gene with a translocation from chromosome 10 to chromosome 1 compared with the tomato genome. Parental genotypes for the three genes were in agreement with the identification of the candidate genes performed in the S3MEGGIC population. Our new eggplant MAGIC population is the largest recombinant population in eggplant and is a powerful tool for eggplant genetics and breeding studies.

Transcriptomic Analysis Revealed Reactive Oxygen Species Scavenging Mechanisms Associated With Ferrous Iron Toxicity in Aromatic Keteki Joha Rice.

Lowland acidic soils with water-logged regions are often affected by ferrous iron (Fe2+) toxicity, a major yield-limiting factor of rice production. Under severe Fe2+ toxicity, reactive oxygen species (ROS) are crucial, although molecular mechanisms and associated ROS homeostasis genes are still unknown. In this study, a comparative RNA-Seq based transcriptome analysis was conducted to understand the Fe2+ toxicity tolerance mechanism in aromatic Keteki Joha. About 69 Fe homeostasis related genes and their homologs were identified, where most of the genes were downregulated. Under severe Fe2+ toxicity, the biosynthesis of amino acids, RNA degradation, and glutathione metabolism were induced, whereas phenylpropanoid biosynthesis, photosynthesis, and fatty acid elongation were inhibited. The mitochondrial iron transporter (OsMIT), vacuolar iron transporter 2 (OsVIT2), ferritin (OsFER), vacuolar mugineic acid transporter (OsVMT), phenolic efflux zero1 (OsPEZ1), root meander curling (OsRMC), and nicotianamine synthase (OsNAS3) were upregulated in different tissues, suggesting the importance of Fe retention and sequestration for detoxification. However, several antioxidants, ROS scavenging genes and abiotic stress-responsive transcription factors indicate ROS homeostasis as one of the most important defense mechanisms under severe Fe2+ toxicity. Catalase (CAT), glutathione (GSH), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) were upregulated. Moreover, abiotic stress-responsive transcription factors, no apical meristem (NAC), myeloblastosis (MYB), auxin response factor (ARF), basic helix-loop-helix (bZIP), WRKY, and C2H2-zinc finger protein (C2H2-ZFP) were also upregulated. Accordingly, ROS homeostasis has been proposed as an essential defense mechanism under such conditions. Thus, the current study may enrich the understanding of Fe-homeostasis in rice.

Transcriptomics Analysis of Wheat Tassel Response to Tilletia laevis Kühn, Which Causes Common Bunt of Wheat.

Tilletia laevis Kühn [synonym T. foetida (Wallr.) Liro] can lead to a wheat common bunt, which is one of the most serious diseases affecting kernels, a serious reduction in grain yield, and losses can reach up to 80% in favorable environments. To understand how wheat tassels respond to T. laevis, based on an RNA-Seq technology, we analyzed a host transcript accumulation on healthy wheat tassels and on tassels infected by the pathogen. Our results showed that 7,767 out of 15,658 genes were upregulated and 7,891 out of 15,658 genes were downregulated in wheat tassels. Subsequent gene ontology (GO) showed that differentially expressed genes (DEGs) are predominantly involved in biological processes, cellular components, and molecular functions. Additionally, Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that 20 pathways were expressed significantly during the infection of wheat with T. laevis, while biosynthesis of amino acids, carbon metabolism, and starch and sucrose metabolism pathways were more highly expressed. Our findings also demonstrated that genes involved in defense mechanisms and myeloblastosis (MYB) transcription factor families were mostly upregulated, and the RNA-seq results were validated by quantitative real-time polymerase chain reaction (qRT-PCR). This is the first report on transcriptomics analysis of wheat tassels in response to T. laevis, which will contribute to understanding the interaction of T. laevis and wheat, and may provide higher efficiency control strategies, including developing new methods to increase the resistance of wheat crops to T. laevis-caused wheat common bunt.

Artemisinin potentiates apoptosis and triggers cell cycle arrest to attenuate malignant growth of salivary gland tumor cells.

One of the rare malignant tumors developing within the glands of the buccal cavity in human beings is salivary gland tumors (SGTs). The hallmark of SGTs is the fusion of nuclear factor IB (NFIB) and myeloblastosis (MYB) genes developed after the translocation of q22-23; p23-24. Although the aetiology of SGTs is not clear, however, the therapeutic modalities are surgical resection followed by the combination of chemotherapy and radiotherapy if a chance of recurrence seems to develop. Owing to have numerous side effects of chemotherapy, the drug development has been shifted to natural products with minimal side effects. One of the key phytochemical artemisinin derived from wormwood Artemisia annua exhibits various pharmacological activities against various in-vivo and in-vitro cellular models. Here, we evaluated the cytotoxic potential of artemisinin against A-253 cells with possible underlying cell death mechanisms. Our results showed that artemisinin reduces the proliferation of cells in a concentration-dependent manner and displays IC50 value in a range of 10.23, 14.21 μM, and 203.18 μM against A-253/HTB-41 and transformed salivary gland SMIE cells, respectively. Flow cytometry analysis demonstrated that artemisinin promotes a significant amount of apoptotic cellular population and triggers G0/G1 arrest of A-253 cells in a concentration-dependent manner. To verify the mechanism of cell death induced by artemisinin in A-253 cells, we found an increased level of Bax, Bim, Bad, Bak and reduced level of antiapoptotic protein Bcl-2, Bcl-XL with concomitant release of mitochondrial resident protein cytochrome c into the cytoplasm. Additionally, we found that artemisinin augments the production of reactive oxygen species which further leads to the activation of proapoptotic proteins PARP1, and caspase-3, in a concentration-dependent manner thereby triggering apoptosis. In conclusion, artemisinin exhibits promising anticancer therapeutic potential against A-253 cells and needs further validation of in-vitro results in preclinical models.

Independent Evolution of the MYB Family in Brown Algae.

Myeloblastosis (MYB) proteins represent one of the largest families of eukaryotic transcription factors and regulate important processes in growth and development. Studies on MYBs have mainly focused on animals and plants; however, comprehensive analysis across other supergroups such as SAR (stramenopiles, alveolates, and rhizarians) is lacking. This study characterized the structure, evolution, and expression of MYBs in four brown algae, which comprise the biggest multicellular lineage of SAR. Subfamily 1R-MYB comprised heterogeneous proteins, with fewer conserved motifs found outside the MYB domain. Unlike the SHAQKY subgroup of plant 1R-MYB, THAQKY comprised the largest subgroup of brown algal 1R-MYBs. Unlike the expansion of 2R-MYBs in plants, brown algae harbored more 3R-MYBs than 2R-MYBs. At least ten 2R-MYBs, fifteen 3R-MYBs, and one 6R-MYB orthologs existed in the common ancestor of brown algae. Phylogenetic analysis showed that brown algal MYBs had ancient origins and a diverged evolution. They showed strong affinity with stramenopile species, while not with red algae, green algae, or animals, suggesting that brown algal MYBs did not come from the secondary endosymbiosis of red and green plastids. Sequence comparison among all repeats of the three types of MYB subfamilies revealed that the repeat of 1R-MYBs showed higher sequence identity with the R3 of 2R-MYBs and 3R-MYBs, which supports the idea that 1R-MYB was derived from loss of the first and second repeats of the ancestor MYB. Compared with other species of SAR, brown algal MYB proteins exhibited a higher proportion of intrinsic disordered regions, which might contribute to multicellular evolution. Expression analysis showed that many MYB genes are responsive to different stress conditions and developmental stages. The evolution and expression analyses provided a comprehensive analysis of the phylogeny and functions of MYBs in brown algae.

Molecular cloning and characterisation of a novel putative MYB-related transcription factor (ClMYB1R1) from Curcuma longa L.

Turmeric (Curcuma longa L.) is gaining immense global importance due to the presence of curcumin that contributes to its immunomodulatory properties. Curcumin, a phenylpropanoid derivative, is the most important secondary metabolite present in turmeric rhizomes and understanding the regulatory mechanism of curcumin biosynthesis is hence important. In plants, activator and repressor type transcription factors (TFs) of the myeloblastosis (MYB) family have been found to regulate the biosynthesis of secondary metabolites. MYB TF genes of the R2R3 class were identified by RNA-Seq based approach from turmeric. The present study involves RNA seq based identification, cloning and characterisation of a novel MYB TF of the 1R class. Gene-specific primers were used to amplify 1R MYB from the rhizome, and it was sequenced to give a full-length gene of 1056 bp. The identified MYB gene was designated as ClMYB1R1 and consisted of a 693 bp open reading frame (ORF) which encodes a 230 amino acid length protein with a molecular mass of 25 kDa and pI 9.51. The protein was predicted to consist of a single helix-turn-helix MYB-like motif and other highly conserved residues. ClMYB1R1 expression varied in different genotypes and tissues. UV-C light was found to upregulate, while NaCl and nutrient stresses down-regulated the expression. The expression showed a positive correlation with a candidate pathway gene ClPKS11 under all of the above experimental conditions, indicating the putative role of ClMYB1R1 in regulating curcumin biosynthesis.

Microbial consortium mediated growth promotion and Arsenic reduction in Rice: An integrated transcriptome and proteome profiling

The adverse effects of arsenic (As) contamination are well known. Rice is a staple food for 50% of the world population but the accumulation of As into rice hampers the food security and safety. Thus the amelioration of As stress and reduction of As levels in rice are needed. In this study, transcriptome (Illumina sequencing) and proteome (2D gel electrophoresis) explored mechanisms of consortium (P. putida+C. vulgaris) mediated growth promotion and As amelioration in rice. The rice seedlings grown hydroponically in the Hewitt nutrient medium and after acclimatization, exposed to 50 µM As alone as well as with microbial consortium to observe the impact at morphological and molecular level. The inoculation of microbial consortium significantly ameliorated the As toxicity, improved growth of root hairs and maintained cellular integrity of the epidermis, exodermis and the stele region during As exposure. Several genes showed differential expression in As and As+P. putida. Down-regulation of As transporters (OsPIP2;2 and OsPIP2;3, OsTIP2;1) and higher expression of WRKY gene (WRKY28) during As+P. putida+C.vulgaris suggested reduction of As uptake in rice. The up-regulation of nutrient elements transporters (OsZIFL9, OsZIFL5, OsZIFL12 and OsZIP2, OsYSL15 and OsCOPT6) in the presence of consortium indicated the improved nutrient status of rice. Higher expression of regulatory elements like auxin/indole 3 acetic acid (AUX/IAA), WRKY and myeloblastosis (MYB) TFs and down-regulation of defense responsive genes such Glutathione-S-transferase, Peroxidase and Glutaredoxinduring As+P. putida+C.vulgaris exposure was also observed. Proteome profiling demonstrated differential abundance of proteins involved in photosynthesis (chlorophyll a/b binding protein, photosystem I Fe-S centre), energy metabolism (ATP synthase subunit beta) transport, signaling (tubulin 1, actin 1), defense (glutathione S-transferase, phenylalanine ammonia lyase) and amino acid metabolism (cysteine synthase, glutamine synthetase), which supported the As ameliorative and growth-promoting potential of microbial consortium during As stress in rice plants. The study gives comprehensive information about gene and protein changes in rice plants in As+consortium exposure.

Characterization of the MYB Genes Reveals Insights Into Their Evolutionary Conservation, Structural Diversity, and Functional Roles in Magnaporthe oryzae.

The myeloblastosis (MYB) transcription factor family is evolutionarily conserved among plants, animals, and fungi, and contributes to their growth and development. We identified and analyzed 10 putative MYB genes in Magnaporthe oryzae (MoMYB) and determined their phylogenetic relationships, revealing high divergence and variability. Although MYB domains are generally defined by three tandem repeats, MoMYBs contain one or two weakly conserved repeats embedded in extensive disordered regions. We characterized the secondary domain organization, disordered segments, and functional contributions of each MoMYB. During infection, MoMYBs are distinctively expressed and can be subdivided into two clades of being either up- or down-regulated. Among these, MoMYB1 and MoMYB8 are up-regulated during infection and vegetative growth, respectively. We found MoMYB1 localized predominantly to the cytosol during the formation of infection structures. ΔMomyb1 exhibited reduced virulence on intact rice leaves corresponding to the diminished ability to form hypha-driven appressorium (HDA). We discovered that MoMYB1 regulates HDA formation on hard, hydrophobic surfaces, whereas host surfaces partially restored HDA formation in ΔMomyb1. Lipid droplet accumulation in hyphal tips and expression of HDA-associated genes were strongly perturbed in ΔMomyb1 indicating genetic interaction of MoMYB1 with downstream components critical to HDA formation. We also found that MoMYB8 is necessary for fungal growth, dark-induced melanization of hyphae, and involved in higher abiotic stress tolerance. Taken together, we revealed a multifaceted picture of the MoMYB family, wherein a low degree of conservation has led to the development of distinct structures and functions, ranging from fungal growth to virulence.

Capsicum chinense MYB Transcription Factor Genes: Identification, Expression Analysis, and Their Conservation and Diversification With Other Solanaceae Genomes.

Myeloblastosis (MYB) genes are important transcriptional regulators of plant growth, development, and secondary metabolic biosynthesis pathways, such as capsaicinoid biosynthesis in Capsicum. Although MYB genes have been identified in Capsicum annuum, no comprehensive study has been conducted on other Capsicum species. We identified a total of 251 and 240 MYB encoding genes in Capsicum chinense MYBs (CcMYBs) and Capsicum baccatum MYBs (CbMYBs). The observation of twenty tandem and 41 segmental duplication events indicated expansion of the MYB gene family in the C. chinense genome. Five CcMYB genes, i.e., CcMYB101, CcMYB46, CcMYB6, CcPHR8, and CcRVE5, and two CaMYBs, i.e., CaMYB3 and CaHHO1, were found within the previously reported capsaicinoid biosynthesis quantitative trait loci. Based on phylogenetic analysis with tomato MYB proteins, the Capsicum MYBs were classified into 24 subgroups supported by conserved amino acid motifs and gene structures. Also, a total of 241 CcMYBs were homologous with 225 C. annuum, 213 C. baccatum, 125 potato, 79 tomato, and 23 Arabidopsis MYBs. Synteny analysis showed that all 251 CcMYBs were collinear with C. annuum, C. baccatum, tomato, potato, and Arabidopsis MYBs spanning over 717 conserved syntenic segments. Using transcriptome data from three fruit developmental stages, a total of 54 CcMYBs and 81 CaMYBs showed significant differential expression patterns. Furthermore, the expression of 24 CcMYBs from the transcriptome data was validated by quantitative real-time (qRT) PCR analysis. Eight out of the 24 CcMYBs validated by the qRT-PCR were highly expressed in fiery hot C. chinense than in the lowly pungent C. annuum. Furthermore, the co-expression analysis revealed several MYB genes clustered with genes from the capsaicinoid, anthocyanin, phenylpropanoid, carotenoid, and flavonoids biosynthesis pathways, and related to determining fruit shape and size. The homology modeling of 126 R2R3 CcMYBs showed high similarity with that of the Arabidopsis R2R3 MYB domain template, suggesting their potential functional similarity at the proteome level. Furthermore, we have identified simple sequence repeat (SSR) motifs in the CcMYB genes, which could be used in Capsicum breeding programs. The functional roles of the identified CcMYBs could be studied further so that they can be manipulated for Capsicum trait improvement.

Integrated metabolome and transcriptome analysis reveals candidate genes involved in metabolism of terpenoids and phthalides in celery seeds

Celery (Apium graveolens L.) seeds have a unique aroma and can be used in the pharmaceutical industry. Terpenoids are the main volatile organic compounds (VOCs) of celery seed essential oil, and phthalides are the source of its aroma. However, thus far, no studies have been conducted on the metabolism of terpenoids and phthalides in celery. In this study, 195 VOCs were detected in celery seeds by using headspace injection combined with gas chromatography–mass spectrometry (GC–MS). The content of 85 VOCs, including 20 terpenoids and 6 phthalides, was found to be significantly different during the five stages of celery seed development. Based on the pattern of changes in the concentrations of terpenoids and phthalides, an integrated transcriptome and metabolome analysis of three developmental celery seed stages was performed. The results showed that 11 differentially expressed structural genes involved in the metabolism of terpenoids have a positive correlation coefficient with 16 terpenoids, while 103 differentially expressed transcription factor genes are correlated with these 11 differentially expressed genes (DEGs). Among these differentially expressed transcription factor genes, two basic helix-loop-helix (bHLH) genes are similar with Arabidopsis thaliana bHLH gene (MYC2), which has already known to be involved in the regulation of terpenoid metabolism. The results of the integrated analysis also revealed that 88 differentially expressed transcription factor genes are related to 6 phthalides, and one myeloblastosis (MYB) gene is similar with petunia MYB gene (ODORANT1), which is involved in the regulation of the metabolism of volatile benzene compounds in petunia (Pharbitis nil) flowers. Therefore, this study has laid a foundation for further research related to the identification of key genes that regulate the metabolism of terpenoids and phthalides in celery. Moreover, these results can contribute significantly to the improvement in the quality of celery seed essential oil.

Genome-Wide Characterization of R2R3-MYB Transcription Factors in Pitaya Reveals a R2R3-MYB Repressor HuMYB1 Involved in Fruit Ripening through Regulation of Betalain Biosynthesis by Repressing Betalain Biosynthesis-Related Genes.

The MYB (myeloblastosis) superfamily constitutes one of the most abundant transcription factors (TFs) regulating various biological processes in plants. However, the molecular characteristics and functions of MYB TFs in pitaya remain unclear. To date, no genome-wide characterization analysis of this gene family has been conducted in the Cactaceae species. In this study, 105 R2R3-MYB members were identified from the genome data of Hylocereus undatus and their conserved motifs, physiological and biochemical characteristics, chromosome locations, synteny relationship, gene structure and phylogeny were further analyzed. Expression analyses suggested that three up-regulated HuMYBs and twenty-two down-regulated HuMYBs were probably involved in fruit ripening of pitaya. Phylogenetic analyses of R2R3-MYB repressors showed that seven HuMYBs (HuMYB1, HuMYB21, HuMYB48, HuMYB49, HuMYB72, HuMYB78 and HuMYB101) were in clades containing R2R3-MYB repressors. HuMYB1 and HuMYB21 were significantly down-regulated with the betalain accumulation during fruit ripening of ‘Guanhuahong’ pitaya (H. monacanthus). However, only HuMYB1 had R2 and R3 repeats with C1, C2, C3 and C4 motifs. HuMYB1 was localized exclusively to the nucleus and exhibited transcriptional inhibition capacities. Dual luciferase reporter assay demonstrated that HuMYB1 inhibited the expression of betalain-related genes: HuADH1, HuCYP76AD1-1 and HuDODA1. These results suggested that HuMYB1 is a potential repressor of betalain biosynthesis during pitaya fruit ripening. Our results provide the first genome-wide analyses of the R2R3-MYB subfamily involved in pitaya betalain biosynthesis and will facilitate functional analysis of this gene family in the future.

Genome-Wide Analysis of Myeloblastosis-Related Genes in Brassica napus L. and Positive Modulation of Osmotic Tolerance by BnMRD107.

Myeloblastosis (MYB)-related transcription factors comprise a large subfamily of the MYB family. They play significant roles in plant development and in stress responses. However, MYB-related proteins have not been comprehensively investigated in rapeseed (Brassica napus L.). In the present study, a genome-wide analysis of MYB-related transcription factors was performed in rapeseed. We identified 251 Brassica napus MYB (BnMYB)-related members, which were divided phylogenetically into five clades. Evolutionary analysis suggested that whole genome duplication and segmental duplication events have played a significant role in the expansion of BnMYB-related gene family. Selective pressure of BnMYB-related genes was estimated using the Ka/Ks ratio, which indicated that BnMYB-related genes underwent strong purifying selection during evolution. In silico analysis showed that various development-associated, phytohormone-responsive, and stress-related cis-acting regulatory elements were enriched in the promoter regions of BnMYB-related genes. Furthermore, MYB-related genes with tissue or organ-specific, stress-responsive expression patterns were identified in B. napus based on temporospatial and abiotic stress expression profiles. Among the stress-responsive MYB-related genes, BnMRD107 was strongly induced by drought stress, and was therefore selected for functional study. Rapeseed seedlings overexpressing BnMRD107 showed improved resistance to osmotic stress. Our findings not only lay a foundation for further functional characterization of BnMYB-related genes, but also provide valuable clues to determine candidate genes for future genetic improvement of B. napus.

Comparative genomic analysis of MYB transcription factors for cuticular wax biosynthesis and drought stress tolerance in Helianthus annuus L.

Sunflower is an important oil-seed crop in Pakistan, it is mainly cultivated in the spring season. It is severely affected by drought stress resulting in lower yield. Cuticular wax acts as the first defense line to protect plants from drought stress condition. It seals the aerial parts of plants and reduce the water loss from leaf surfaces. Various myeloblastosis (MYB) transcription factors (TFs) are involved in biosynthesis of epicuticular waxes under drought-stress. However, less information is available for MYB, TFs in drought stress and wax biosynthesis in sunflower. We used different computational tools to compare the Arabidopsis MYB, TFs involved in cuticular wax biosynthesis and drought stress tolerance with sunflower genome. We identified three putative MYB genes (MYB16, MYB94 and MYB96) in sunflower along with their seven homologs in Arabidopsis. Phylogenetic association of MYB TFs in Arabidopsis and sunflower indicated strong conservation of TFs in plant species. From gene structure analysis, it was observed that intron and exon organization was family-specific. MYB TFs were unevenly distributed on sunflower chromosomes. Evolutionary analysis indicated the segmental duplication of the MYB gene family in sunflower. Quantitative Real-Time PCR revealed the up-regulation of three MYB genes under drought stress. The gene expression of MYB16, MYB94 and MYB96 were found many folds higher in experimental plants than control. The present study provided the first insight into MYB TFs family's characterization in sunflower under drought stress conditions and wax biosynthesis TFs.

Comparative physiological and transcriptomic analyses illuminate common mechanisms by which silicon alleviates cadmium and arsenic toxicity in rice seedlings

The inessential heavy metal/loids cadmium (Cd) and arsenic (As), which often co-occur in polluted paddy soils, are toxic to rice. Silicon (Si) treatment is known to reduce Cd and As toxicity in rice plants. To better understand the shared mechanisms by which Si alleviates Cd and As stress, rice seedlings were hydroponically exposed to Cd or As, then treated with Si. The addition of Si significantly ameliorated the inhibitory effects of Cd and As on rice seedling growth. Si supplementation decreased Cd and As translocation from roots to shoots, and significantly reduced Cd- and As-induced reactive oxygen species generation in rice seedlings. Transcriptomics analyses were conducted to elucidate molecular mechanisms underlying the Si-mediated response to Cd or As stress in rice. The expression patterns of the differentially expressed genes in Cd- or As-stressed rice roots with and without Si application were compared. The transcriptomes of the Cd- and As-stressed rice roots were similarly and profoundly reshaped by Si application, suggesting that Si may play a fundamental, active role in plant defense against heavy metal/loid stresses by modulating whole genome expression. We also identified two novel genes, Os01g0524500 and Os06g0514800, encoding a myeloblastosis (MYB) transcription factor and a thionin, respectively, which may be candidate targets for Si to alleviate Cd and As stress in rice, as well as for the generation of Cd- and/or As-resistant plants. This study provides valuable resources for further clarification of the shared molecular mechanisms underlying the Si-mediated alleviation of Cd and As toxicity in rice.