MYB alternative promoter activity is increased in adenoid cystic carcinoma metastases and is associated with a specific gene expression signature.

OBJECTIVE: Adenoid cystic carcinoma (ACC) is a head and neck cancer with a poor long-term prognosis that shows frequent local recurrences and distant metastases. The tumors are characterized by MYB oncogene activation and are notoriously unresponsive to systemic therapies. The biological underpinnings behind therapy resistance of disseminated ACC are largely unknown. Here, we have studied the molecular and clinical significance of MYB alternative promoter (TSS2) usage in ACC metastases. MATERIALS AND METHODS: MYB TSS2 activity was investigated in primary tumors and metastases from 26 ACC patients using RNA-sequencing and quantitative real-time PCR analysis. Differences in global gene expression between MYB TSS2 high and low cases were studied, and pathway analyses were performed. RESULTS: MYB TSS2 activity was significantly higher in ACC metastases than in primary tumors (median activity 15.1 vs 3.0, P = 0.0003). MYB TSS2 high ACC metastases showed a specific gene expression signature, including increased expression of multi-drug resistance genes and canonical MYB target genes, and suppression of the p53 and NOTCH pathways. CONCLUSIONS: Collectively, our findings indicate that elevated MYB TSS2 activity is associated with metastases, potential drug resistance, and augmented MYB-driven gene expression in ACC. Our study advocates the need for new therapies that specifically target MYB and drug resistance mechanisms in disseminated ACC.

Genome-wide identification, phylogeny and expression analysis of the R2R3-MYB gene family in quinoa (Chenopodium quinoa) under abiotic stress.

The MYB transcription factor (TF) are among the largest gene families of plants being responsible for several biological processes. The R2R3-MYB gene family are integral player regulating plant primary and secondary metabolism, growth and development, and responses to hormones and stresses. The phylogenetic analysis combined with gene structure analysis and motif determination resulted in division of R2R3-MYB gene family into 27 subgroups. Evidence generated from synteny analyses indicated that CqR2R3-MYBs gene family is featured by tandem and segmental duplication events. On the basis of RNA-Seq data, the expression patterns of different tissues under salt treatment were investigated resulting CqR2R3-MYB genes high expression both in roots and stem of quinoa (Chenopodium quinoa ) plants. More than half of CqR2R3-MYB genes showed expression under salt stress. Based on this result, CqR2R3-MYB s may regulate quinoa plant growth development and resistance to abiotic stresses. These findings provided comprehensive insights on role of CqR2R3-MYBs gene family members in quinoa and candidate MYB gene family members can be further studies on their role for abiotic stress tolerance in crop plants.

A novel method to assess copy number variations in melanocytic neoplasms: Droplet digital PCR for precise quantitation of MYC and MYB genes.

INTRODUCTION: While most melanocytic neoplasms can be classified as either benign or malignant by histopathology alone, ancillary molecular diagnostic tests can be necessary to establish the correct diagnosis in challenging cases. Currently, the detection of copy number variations (CNVs) by fluorescence in situ hybridization and chromosomal microarray (CMA) are the most popular methods, but remain expensive and inaccessible. We aim to develop a relatively inexpensive, fast, and accessible molecular assay to detect CNVs relevant to melanoma using droplet digital polymerase chain reaction (ddPCR) technology. METHODS: In this proof-of-concept study, we evaluated CNVs in MYC and MYB genes from 73 cases of benign nevi, borderline melanocytic lesions, and primary and metastatic melanoma at our institution from 2015 to 2022. A multiplexed ddPCR assay and CMA were performed on each sample, and the results were compared. RESULTS: Concordance analysis of ddPCR with CMA for quantification of MYC and MYB CNVs revealed a sensitivity and specificity of 89% and 86% for MYC and 83% and 74% for MYB, respectively. CONCLUSION: We demonstrate the first use of a multiplexed ddPCR assay to identify CNVs in melanocytic neoplasms. With further improvement and validation, ddPCR may represent a low-cost and rapid tool to aid in the diagnosis of histopathologically ambiguous melanocytic tumors.

Identification of MYB gene family and functional analysis of GhMYB4 in cotton (Gossypium spp.).

Myeloblastosis (MYB) transcription factors (TFs) form a large gene family involved in a variety of biological processes in plants. Little is known about their roles in the development of cotton pigment glands. In this study, 646 MYB members were identified in Gossypium hirsutum genome and phylogenetic classification was analyzed. Evolution analysis revealed assymetric evolution of GhMYBs during polyploidization and sequence divergence of MYBs in G. hirustum was preferentially happend in D sub-genome. WGCNA (weighted gene co-expression network analysis) showed that four modules had potential relationship with gland development or gossypol biosynthesis in cotton. Eight differentially expressed GhMYB genes were identified by screening transcriptome data of three pairs of glanded and glandless cotton lines. Of these, four were selected as candidate genes for cotton pigment gland formation or gossypol biosynthesis by qRT-PCR assay. Silencing of GH_A11G1361 (GhMYB4) downregulated expression of multiple genes in gossypol biosynthesis pathway, indicating it could be involved in gossypol biosynthesis. The potential protein interaction network suggests that several MYBs may have indirect interaction with GhMYC2-like, a key regulator of pigment gland formation. Our study was the systematic analysis of MYB genes in cotton pigment gland development, providing candidate genes for further study on the roles of cotton MYB genes in pigment gland formation, gossypol biosynthesis and future crop plant improvement.

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.

Genome-Wide Comparative Analysis of the R2R3-MYB Gene Family in Five Solanaceae Species and Identification of Members Regulating Carotenoid Biosynthesis in Wolfberry.

The R2R3-MYB is a large gene family involved in various plant functions, including carotenoid biosynthesis. However, this gene family lacks a comprehensive analysis in wolfberry (Lycium barbarum L.) and other Solanaceae species. The recent sequencing of the wolfberry genome provides an opportunity for investigating the organization and evolutionary characteristics of R2R3-MYB genes in wolfberry and other Solanaceae species. A total of 610 R2R3-MYB genes were identified in five Solanaceae species, including 137 in wolfberry. The LbaR2R3-MYB genes were grouped into 31 subgroups based on phylogenetic analysis, conserved gene structures, and motif composition. Five groups only of Solanaceae R2R3-MYB genes were functionally divergent during evolution. Dispersed and whole duplication events are critical for expanding the R2R3-MYB gene family. There were 287 orthologous gene pairs between wolfberry and the other four selected Solanaceae species. RNA-seq analysis identified the expression level of LbaR2R3-MYB differential gene expression (DEGs) and carotenoid biosynthesis genes (CBGs) in fruit development stages. The highly expressed LbaR2R3-MYB genes are co-expressed with CBGs during fruit development. A quantitative Real-Time (qRT)-PCR verified seven selected candidate genes. Thus, Lba11g0183 and Lba02g01219 are candidate genes regulating carotenoid biosynthesis in wolfberry. This study elucidates the evolution and function of R2R3-MYB genes in wolfberry and the four Solanaceae species.

Genome-Wide Identification, Classification and Expression Analysis of the MYB Transcription Factor Family in Petunia.

A lot of researches have been focused on the evolution and function of MYB transcription factors (TFs). For revealing the formation of petunia flower color diversity, MYB gene family in petunia was identified and analyzed. In this study, a total of 155 MYB genes, including 40 1R-MYBs, 106 R2R3-MYBs, 7 R1R2R3-MYBs and 2 4R-MYBs, have been identified in the Petunia axillaris genome. Most R2R3 genes contain three exons and two introns, whereas the number of PaMYB introns varies from 0 to 12. The R2R3-MYB members could be divided into 28 subgroups. Analysis of gene structure and protein motifs revealed that members within the same subgroup presented similar exon/intron and motif organization, further supporting the results of phylogenetic analysis. Genes in subgroup 10, 11 and 21 were mainly expressed in petal, not in vegetative tissues. Genes in subgroup 9, 19, 25 and 27 expressed in all tissues, but the expression patterns of each gene were different. According to the promoter analysis, five R2R3-MYB and two MYB-related genes contained MBSI cis-element, which was involved in flavonoid biosynthetic regulation. PaMYB100/DPL has been reported to positively regulate to pigmentation. However, although PaMYB82, PaMYB68 and Pa1RMYB36 contained MBSI cis-element, their function in flavonoid biosynthesis has not been revealed. Consistent with existing knowledge, PaMYBs in subgroup 11 had similar function to AtMYBs in subgroup 6, genes in which played an important role in anthocyanin biosynthesis. In addition, PaMYB1 and PaMYB40 belonged to P9 (S7) and were potentially involved in regulation of flavonoid synthesis in petunia vegetative organs. This work provides a comprehensive understanding of the MYB gene family in petunia and lays a significant foundation for future studies on the function and evolution of MYB genes in petunia.

High promoter sequence variation in subgroup 6 members of R2R3-MYB genes is involved in different floral anthocyanin color patterns in Lilium spp.

The spatially and temporally distinct expression of R2R3-MYB positive regulators is among the major mechanisms that create various anthocyanin color patterns in many flowers. However, we do not know how these positive regulators have gained different expression profiles. In the Asiatic hybrid lily 'Lollypop' (derived from the crosses of species belonging to Sinomartagon/Daurolirion section), MYB12 and MYB19S regulate the pigmentation at whole tepals and raised tepal spots, respectively. In the Oriental hybrid lily 'Sorbonne' (derived from the crosses of species belonging to the Archelirion section), MYB12 regulates both whole tepal and raised spot pigmentation. The genes have similar amino acid sequences with similar protein functions but exhibit different expression profiles in lily flowers. As promoters are among the most significant factors affecting gene expression profiles, their promoter sequences were determined in this study. The three genes had very different promoter sequences, and putative cis-regulatory elements were not conserved in numbers or order. To further confirm the promoter functions, tobacco plants were transformed with native promoter-driven MYB12 or MYB19S genes of 'Lollypop.' Expression levels of MYB12 were higher in corolla tubes than in lobes, while those of MYB19S were higher in corolla lobes than in tubes. Thus, the diverse promoter functions were likely to be the leading causes of their different expression profiles and generation of unique color patterns. Finally, the history of R2R3-MYB gene establishment during lily evolution was estimated using sequence data.

Genome-wide analysis and expression profiles of the StR2R3-MYB transcription factor superfamily in potato (Solanum tuberosum L.).

MYB transcription factors comprise one of the largest families in plant kingdom, which play a variety of functions in plant developmental processes and defence responses, the R2R3-MYB members are the predominant form found in higher plants. In the present study, a total of 111 StR2R3-MYB transcription factors were identified and further phylogenetically classified into 31 subfamilies, as supported by highly conserved gene structures and motifs. Collinearity analysis showed that the segmental duplication events played a crucial role in the expansion of StR2R3-MYB gene family. Synteny analysis indicated that 37 and 13 StR2R3-MYB genes were orthologous to Arabidopsis and wheat (Triticum aestivum), respectively, and these gene pairs have evolved under strong purifying selection. RNA-seq data from different tissues and abiotic stresses revealed tissue-preferential and abiotic stress-responsive StR2R3-MYB genes. We further analyzed StR2R3-MYB genes might be involved in anthocyanin biosynthesis and drought stress by using RNA-seq data of pigmented tetraploid potato cultivars and drought-sensitive and -tolerant tetraploid potato cultivars under drought stress, respectively. Moreover, EAR motifs were found in 21 StR2R3-MYB proteins and 446 pairs of proteins were predicted to interact with 21 EAR motif-containing StR2R3-MYB proteins by constructing the interaction network with medium confidence (0.4). Additionally, Gene Ontology (GO) analysis of the 21 EAR motif-containing StR2R3-MYB proteins was performed to further investigate their functions. This work will facilitate future biologically functional studies of potato StR2R3-MYB transcription factors and enrich the knowledge of MYB superfamily genes in plant species.

Single-repeat R3 MYB transcription factors from Platanus acerifolia negatively regulate trichome formation in Arabidopsis.

MAIN CONCLUSION: Four R3 MYB genes were cloned and identified from Platanus acerifolia and analysed according to endogenous gene expression profiles, protein-protein interaction patterns, phenotypic effects and related gene expression profiles in transgenic Arabidopsis, suggesting that London plane R3 MYB genes inhibit trichome formation in Arabidopsis. The CPC-like MYB transcription factors including CAPRICE (CPC), TRIPTYCHON (TRY), ENHANCER OF TRY AND CPC 1, 2 and 3 (ETC1, ETC2 and ETC3), TRICHOMELESS1 (TCL1) and TRICHOMELESS2(TCL2) play important roles in controlling trichome patterning in Arabidopsis. In this study, four sequences homologous with the Arabidopsis CPC family were identified from London plane and named PaTRY, PaCPC-like1, PaCPC-like2 and PaCPC-like3. Over-expression of PaTRY, PaCPC-like1, PaCPC-like2 and PaCPC-like3 in Arabidopsis resulted in glabrous phenotypes. In addition, expression of endogenous GL2, GL1, MYB23, TTG2 and a set of R3 MYB-encoding genes was markedly reduced. Furthermore, the protein products of PaTRY, PaCPC-like1, PaCPC-like2 and PaCPC-like3 were shown to interact with PaGL3 in yeast two-hybrid assays. Together, these results likely suggest that the mechanisms of trichome regulation in London plane have similarities with those in Arabidopsis.

Proto-oncogenes in a eukaryotic unicellular organism play essential roles in plasmodial growth in host cells.

BACKGROUND: The eukaryotic unicellular protist Plasmodiophora brassicae is an endocellular parasite of cruciferous plants. In host cortical cells, this protist develops a unicellular structure that is termed the plasmodium. The plasmodium is actually a multinucleated cell, which subsequently splits and forms resting spores. The mechanism for the growth of this endocellular parasite in host cell is unclear. RESULTS: Here, combining de novo genome sequence and transcriptome analysis of strain ZJ-1, we identified top five significant enriched KEGG pathways of differentially expressed genes (DEGs), namely translation, cell growth and death, cell communication, cell motility and cancers. We detected 171 proto-oncogenes from the genome of P. brassicae that were implicated in cancer-related pathways, of which 46 were differential expression genes. Three predicted proto-oncogenes (Pb-Raf1, Pb-Raf2, and Pb-MYB), which showed homology to the human proto-oncogenes Raf and MYB, were specifically activated during the plasmodial growth in host cortical cells, demonstrating their involvement in the multinucleate development stage of the unicellular protist organism. Gene networks involved in the tumorigenic-related signaling transduction pathways and the activation of 12 core genes were identified. Inhibition of phosphoinositol-3-kinase relieved the clubroot symptom and significantly suppressed the development process of plasmodia. CONCLUSIONS: Proto-oncogene-related regulatory mechanisms play an important role in the plasmodial growth of P. brassicae.

Overexpression of ScMYBAS1 alternative splicing transcripts differentially impacts biomass accumulation and drought tolerance in rice transgenic plants.

Drought is the most significant environmental stress for agricultural production worldwide, and tremendous efforts have been made to improve crop yield under the increasing water scarcity. Transcription factors are major players in the regulation of water stress-related genes in plants. Recently, different MYB transcription factors were characterized for their involvement in drought response. A sugarcane R2R3-MYB gene (ScMYBAS1) and its four alternative forms of transcript (ScMYAS1-2, ScMYBAS1-3, ScMYBAS1-4 and ScMYBAS1-5) were identified in this study. The subcellular localization, in Nicotiniana benthamiana, of the TFs fused in frame with GFP revealed that ScMYBAS1-2-GFP and ScMYBAS1-3-GFP were observed in the nucleus. The overexpression of ScMYBAS1-2 and ScMYBAS1-3 spliced transcripts in rice promoted change in plant growth under both well-watered and drought conditions. The ScMYBAS1-2 and ScMYBAS1-3 transgenic lines revealed a higher relative water content (RWC) compared to the wild type before maximum stress under drought conditions. The ScMYBAS1-2 transgenic lines showed a reduction in biomass (total dry weight). Conversely, ScMYBAS1-3 showed an increased biomass (total dry weight) relative to the wild-type. The overexpression of ScMYBAS1-3 in rice transgenic lines showed involvement with drought tolerance and biomass and, for this reason, was considered a good target for plant transformation, particularly for use in developing genotypes with drought tolerance and biomass accumulation.

Study on the Role of Polymorphisms of the SOX-6 and MYB Genes and Fetal Hemoglobin Levels in Sicilian Patients with ß-Thalassemia and Sickle Cell Disease.

The hemoglobinopathies, as ß-thalassemia (ß-thal) and sickle cell disease, are the most common hereditary hemolytic anemias. The increase of fetal hemoglobin (Hb F) levels can ameliorate the symptoms of hemoglobinopathies. There are several transcription factors such as MYB and SOX-6, which are involved in the regulation of Hb F. There are not enough studies investigating the association between single nucleotide polymorphisms (SNPs) of the SOX-6 and MYB genes and the variation of Hb F levels in patients affected by sickle cell disease and ß-thal. We therefore decided to analyze the role of four missense variants of MYB and SOX-6 genes in the regulation of Hb F levels. In order to do so, we examinated 30 Sicilian patients affected by sickle cell disease and ß-thal, to understand if these variants could also have an influence in our populations. Comparing two groups of patients with low and high levels of Hb F, we found no significant differences in the genetic distribution and allelic frequency of MYB and SOX-6 gene polymorphisms. We also created and compared a 'high producer' and 'low producer' genotype with different genes achieving the same result of no significant difference. Our results may be due either to the fact that the association between these genes and the regulation of Hb F levels are influenced by environmental history and population genetics, or to the small number of samples being analyzed.

Characterization and functional analysis of a MYB gene (GbMYBFL) related to flavonoid accumulation in Ginkgo biloba.

Flavonoids are a group of metabolites in Ginkgo biloba thought to provide health benefits. R2R3-MYB transcription factors (TFs) play key roles in the transcriptional regulation of the flavonoid biosynthesis in plants. In this study, an R2R3-MYB transcription factor gene, GbMYBFL, was isolated from G. biloba and characterized. Results of bioinformatic analysis indicated that GbMYBFL is more closely related to the R2R3-MYB involved in flavonoid biosynthesis and displayed high similarity to MYB from other plants. The genmomic sequence of GbMYBFL had three exons and two introns, with its upstream sequence containing cis-acting regulatory elements Myb binding site, Myc recognition sites, and light, SA, MeJA responsive elements. Subcellular localization analysis indicates that GbMYBFL was located in the nucleus. Quantitative real-time PCR revealed that GbMYBFL was expressed in leaves, stems, roots, young fruits, male flower and female flower, and the level of transcription in male flower and leaves were higher than that in female flower, stems, roots, and young fruits. During G. biloba leaf growth, the transcription of GbMYBFL is positively correlated with the flavonoid content, suggesting that the GbMYBFL is involved in the flavonoid biosynthesis. Overexpression of GbMYBFL under the control of the CaMV35S promoter in Ginkgo callus notably enhanced the accumulation of flavonoids and anthocyanin compared with non-transformed callus. This finding suggested that GbMYBFL positively related to flavonoid biosynthesis, and the overexpression of GbMYBFL was sufficient to induce flavonoids and anthocyanin accumulation.

Recurrent 8q24 rearrangement in blastic plasmacytoid dendritic cell neoplasm: association with immunoblastoid cytomorphology, MYC expression, and drug response.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare skin-tropic hematological malignancy of uncertain pathogenesis and poor prognosis. We examined 118 BPDCN cases for cytomorphology, MYC locus rearrangement, and MYC expression. Sixty-two (53%) and 41 (35%) cases showed the classic and immunoblastoid cytomorphology, respectively. Forty-one (38%) MYC+BPDCN (positive for rearrangement and expression) and 59 (54%) MYC-BPDCN (both negative) cases were identified. Immunoblastoid cytomorphology was significantly associated with MYC+BPDCN. All examined MYC+BPDCNs were negative for MYB/MYBL1 rearrangement (0/36). Clinically, MYC+BPDCN showed older onset, poorer outcome, and localized skin tumors more commonly than MYC-BPDCN. MYC was demonstrated by expression profiling as one of the clearest discriminators between CAL-1 (MYC+BPDCN) and PMDC05 (MYC-BPDCN) cell lines, and its shRNA knockdown suppressed CAL-1 viability. Inhibitors for bromodomain and extra-terminal protein (BETis), and aurora kinases (AKis) inhibited CAL-1 growth more effectively than PMDC05. We further showed that a BCL2 inhibitor was effective in both CAL-1 and PMDC05, indicating that this inhibitor can be used to treat MYC-BPDCN, to which BETis and AKis are probably less effective. Our data will provide a rationale for the development of new treatment strategies for patients with BPDCN, in accordance with precision medicine.

Inducible disruption of the c-myb gene allows allogeneic bone marrow transplantation without irradiation.

Allogeneic bone marrow (BM) transplantation enables the in vivo functional assessment of hematopoietic cells. As pre-conditioning, ionizing radiation is commonly applied to induce BM depletion, however, it exerts adverse effects on the animal and can limit experimental outcome. Here, we provide an alternative method that harnesses conditional gene deletion to ablate c-myb and thereby deplete BM cells, hence allowing BM substitution without other pre-conditioning. The protocol results in a high level of blood chimerism after allogeneic BM transplantation, whereas immune cells in peripheral tissues such as resident macrophages are not replaced. Further, mice featuring a low chimerism after initial transplantation can undergo a second induction cycle for efficient deletion of residual BM cells without the necessity to re-apply donor cells. In summary, we present an effective c-myb-dependent genetic technique to generate BM chimeras in the absence of irradiation or other methods for pre-conditioning.

YB-1 promotes laryngeal squamous cell carcinoma progression by inducing miR-155 expression via c-Myb.

AIM: In this study, we investigated the role of Y-box binding protein-1 (YB-1), c-Myb and miR-155 in human laryngeal squamous cell carcinoma (LSCC) progression. MATERIALS & METHODS: Quantitative real-time PCR, western blot, MTT and Transwell were conducted to determine the expression and function of YB-1/miR-155 pathway. Univariate and multivariate analyses were used to determine the prognostic factors. RESULTS: Expression of YB-1, c-Myb and miR-155 was higher in LSCC tissues. YB-1 promoted proliferation, invasiveness and migration of Hep-2 cells in vitro. Patients with higher YB-1 correlated with advanced T stage, poor differentiation and cervical metastasis. LSCC patients with high YB-1 expression showed poor overall survival. CONCLUSION: YB-1 promotes LSCC progression by increasing miR-155 levels via c-Myb and acts as a prognostic factor.

Three MYB genes co-regulate the phloem-based defence against English grain aphid in wheat.

Plant phloem-based defence (PBD) against phloem-feeding insects is characteristic of the sieve occlusion by phloem lectins and ß-1,3-glucan callose, both of which are produced under regulation by ethylene and MYB transcription factors. Wheat PBD requires ß-1,3-glucan synthase-like proteins GSL2, GSL10, and GSL12, and may also require insect-resistant mannose-binding lectins Hfr-1 and Wci-1, which can accumulate in the phloem upon aphid feeding. This study elucidates whether any of the 73 MYB genes identified previously in the common wheat Triticum aestivum genome plays a role in wheat PBD activation with regard to the GSLs and lectins. Wheat MYB genes TaMYB19, TaMYB29, and TaMYB44 are highly activated in response to infestation of English grain aphid, and their silencing facilitates aphid feeding on wheat phloem and represses wheat PBD responses. Repressed PBD is shown to decrease aphid-induced callose deposition in wheat leaf epidermis and decrease aphid-induced expression of genes GSL2, GSL10, GSL12, Hfr-1, and Wci-1 in wheat leaf tissues. Based on single gene silencing effects, TaMYB19, TaMYB29, and TaMYB44 contribute 55-82% of PBD responses. However, the contributions of TaMYB genes to PBD are eliminated by ethylene signalling inhibitors, while simultaneous silencing of the three TaMYB genes cancels the tested PBD responses. Therefore, TaMYB19, TaMYB29, and TaMYB44 are co-regulators of wheat PBD and execute this function through crosstalk with the ethylene signalling pathway.

GaMYB85, an R2R3 MYB gene, in transgenic Arabidopsis plays an important role in drought tolerance.

BACKGROUND: MYB transcription factors (TFs) are one of the largest families of TFs in higher plants and are involved in diverse biological, functional, and structural processes. Previously, very few functional validation studies on R2R3 MYB have been conducted in cotton in response to abiotic stresses. In the current study, GaMYB85, a cotton R2R3 MYB TF, was ectopically expressed in Arabidopsis thaliana (Col-0) and was functionally characterized by overexpression in transgenic plants. RESULTS: The in-silico analysis of GaMYB85 shows the presence of a SANT domain with a conserved R2R3 MYB imperfect repeat. The GaMYB85 protein has a 257-amino acid sequence, a molecular weight of 24.91 kD, and an isoelectric point of 5.58. Arabidopsis plants overexpressing GaMYB85 exhibited a higher seed germination rate in response to mannitol and salt stress, and higher drought avoidance efficiency than wild-type plants upon water deprivation. These plants had notably higher levels of free proline and chlorophyll with subsequent lower water loss rates and higher relative water content. Germination of GaMYB85 transgenics was more sensitive to abscisic acid (ABA) and extremely liable to ABA-induced inhibition of primary root elongation. Moreover, when subjected to treatment with different concentrations of ABA, transgenic plants with ectopically expressed GaMYB85 showed reduced stomatal density, with greater stomatal size and lower stomatal opening rates than those in wild-type plants. Ectopic expression of GaMYB85 led to enhanced transcript levels of stress-related marker genes such as RD22, ADH1, RD29A, P5CS, and ABI5. CONCLUSIONS: Our results indicate previously unknown roles of GaMYB85, showing that it confers good drought, salt, and freezing tolerance, most probably via an ABA-induced pathway. These findings can potentially be exploited to develop improved abiotic stress tolerance in cotton plants.

Performance Testing of RREB1, MYB, and CCND1 Fluorescence In Situ Hybridization in Spindle-Cell and Desmoplastic Melanoma Argues for a Two-Step Test Algorithm.

BACKGROUND: Diagnostic confirmation of spindle-cell melanoma (SM) or desmoplastic melanoma (DM) as a melanoma can be challenging. In conventional melanoma (CM), a recently established fluorescence in situ hybridization (FISH) assay for RREB1, MYB, CCND1 can be helpful. Here, we determined the presence of RREB1, MYB, and CCND1 abnormalities in an SM/DM/mixed cohort. METHODS: We assembled 49 cases and performed 3 separate hybridizations for RREB1/MYB/CCND1. We assessed clinical utility in diagnostically challenging cases and performed a cost and turnaround time analysis. RESULTS: With regard to the diagnosis of melanoma, the FISH assay is 76% sensitive (n = 31/41 true positives melanomas) and 88% specific (n = 1/8 false positive desmoplastic nevi). The prevalence of abnormalities in DM is lower (12/19 cases, 63%; P = .03) than in SM (15/18 cases, 83%; P = .27), mixed (4 of 4 cases), or the reported sensitivity in CM (345/411 cases, 84%). The implied genetic differences in DM result in a higher false negative rate in DM (37%). Despite these limitations, when restricted to diagnostically challenging cases (n = 23), the FISH assay and, in particular, RREB1 was able to confirm melanoma in 70% (n = 16/23). Individual probe sensitivities ( RREB1 > MYB > CCND1) and a cost and turnaround time analysis argues for a 2-step test algorithm that reduces the economic impact of FISH testing considerably (~55%; n = 69 vs 123 hybridizations). CONCLUSION: We propose a step-by-step genetic testing algorithm to support the diagnosis of melanoma in the setting of SM/DM and show that FISH testing is useful in diagnostically challenging cases.