RAD gene family analysis in cotton provides some key genes for flowering and stress tolerance in upland cotton G. hirsutum.

BACKGROUND: RADIALIS (RAD), belongs to the MYB gene family and regulates a variety of functions including floral dorsoventral asymmetry in Antirrhinum majus and development of fruit proteins in Solanum lycopersicum. RAD genes contain an SNF2_N superfamily domain. Here, we comprehensively identified 68 RAD genes from six different species including Arabidopsis and five species of cotton. RESULTS: Phylogenetic analysis classified RAD genes into five groups. Gene structure, protein motifs and conserved amino acid residues indicated that GhRAD genes were highly conserved during the evolutionary process. Chromosomal location information showed that GhRAD genes were distributed unevenly on different chromosomes. Collinearity and selection pressure analysis indicated RAD gene family expansion in G. hirsutum and G. barbadense with purifying selection pressure. Further, various growth and stress related promotor cis-acting elements were observed. Tissue specific expression level indicated that most GhRAD genes were highly expressed in roots and flowers (GhRAD2, GhRAD3, GhRAD4 and GhRAD11). Next, GhRAD genes were regulated by phytohormonal stresses (JA, BL and IAA). Moreover, Ghi-miRN1496, Ghi-miR1440, Ghi-miR2111b, Ghi-miR2950a, Ghi-miR390a, Ghi-miR390b and Ghi-miR7495 were the miRNAs targeting most of GhRAD genes. CONCLUSIONS: Our study revealed that RAD genes are evolutionary conserved and might be involved in different developmental processes and hormonal stress response. Data presented in our study could be used as the basis for future studies of RAD genes in cotton.

Identification, evolutionary analysis and functional diversification of RAV gene family in cotton (G. hirsutum L.).

MAIN CONCLUSION: Genome wide analysis, expression pattern analysis, and functional characterization of RAV genes highlight their roles in roots, stem development and hormonal response. RAV (Related to ABI3 and VP1) gene family members have been involved in tissues/organs growth and hormone signaling in various plant species. Here, we identified 247 RAVs from 12 different species with 33 RAV genes from G. hirsutum. Phylogenetic analysis classified RAV genes into four distinct groups. Analysis of gene structure showed that most GhRAVs lack introns. Motif distribution pattern and protein sequence logos indicated that GhRAV genes were highly conserved during the process of evolution. Promotor cis-acting elements revealed that promotor regions of GhRAV genes encode numerous elements related to plant growth, abiotic stresses and phytohormones. Chromosomal location information showed uneven distribution of 33 GhRAV genes on different chromosomes. Collinearity analysis identified 628 and 52 orthologous/ paralogous gene pairs in G. hirsutum and G. barbadense, respectively. Ka/Ks values indicated that GhRAV and GbRAV genes underwent strong purifying selection pressure. Selecton model and codon model selection revealed that GhRAV amino acids were under purifying selection and adaptive evolution exists among GhRAV proteins. Three dimensional structure of GhRAVs indicated the presence of numerous alpha helix and beta-barrels. Expression level revealed that some GhRAV genes exhibited high expression in roots (GhRAV3, GhRAV4, GhRAV11, GhRAV18, GhRAV20 and GhRAV30) and stem (GhRAV3 and GhRAV18), indicating their potential role in roots and stem development. GhRAV genes can be regulated by phytohormonal stresses (BL, JA and IAA). Our study provides a reference for future studies related to the functional analysis of GhRAVs in cotton.

Functional characterization of TBL genes revealed the role of GhTBL7 and GhTBL58 in cotton fiber elongation.

TBL (Trichome Birefringence Like) gene family members are involved in trichome initiation and xylan acetylation in several plant species. In our research, we identified 102 TBLs from G. hirsutum. The phylogenetic tree classified TBL genes into five groups. Collinearity analysis of TBL genes indicated 136 paralogous gene pairs in G. hirsutum. Gene duplication indicated that WGD or segmental duplication contributed to the GhTBL gene family expansion. Promoter cis-elements of GhTBLs were related to growth and development, seed-specific regulation, light, and stress responses. GhTBL genes (GhTBL7, GhTBL15, GhTBL21, GhTBL25, GhTBL45, GhTBL54, GhTBL67, GhTBL72, and GhTBL77) exhibited upregulated response under exposure to cold, heat, NaCl, and PEG. GhTBL genes exhibited high expression during fiber development stages. Two GhTBL genes (GhTBL7 and GhTBL58) showed differential expression at 10 DPA fiber, as 10 DPA is a fast fiber elongation stage and fiber elongation is a very important stage of cotton fiber development. Subcellular localization of GhTBL7 and GhTBL58 revealed that these genes reside inside the cell membrane. Promoter GUS activity of GhTBL7 and GhTBL58 exhibited deep staining in roots. To further validate the role of these genes in cotton fiber elongation, we silenced these genes and observed a significant reduction in the fiber length at 10 DPA. In conclusion, the functional study of cell membrane-associated genes (GhTBL7 and GhTBL58) showed deep staining in root tissues and potential function during cotton fiber elongation at 10 DPA fiber.

Genome-wide identification and expression profile of GhGRF gene family in Gossypium hirsutum L.

Background: Cotton is the primary source of renewable natural fiber in the textile industry and an important biodiesel crop. Growth regulating factors (GRFs) are involved in regulating plant growth and development. Methods: Using genome-wide analysis, we identified 35 GRF genes in Gossypium hirsutum. Results: Chromosomal location information revealed an uneven distribution of GhGRF genes, with maximum genes on chromosomes A02, A05, and A12 from the At sub-genome and their corresponding D05 and D12 from the Dt sub-genome. In the phylogenetic tree, 35 GRF genes were divided into five groups, including G1, G2, G3, G4, and G5. The majority of GhGRF genes have two to three introns and three to four exons, and their deduced proteins contained conserved QLQ and WRC domains in the N-terminal end of GRFs in Arabidopsis and rice. Sequence logos revealed that GRF genes were highly conserved during the long-term evolutionary process. The CDS of the GhGRF gene can complement MiRNA396a. Moreover, most GhGRF genes transcripts developed high levels of ovules and fibers. Analyses of promoter cis-elements and expression patterns indicated that GhGRF genes play an essential role in regulating plant growth and development by coordinating the internal and external environment and multiple hormone signaling pathways. Our analysis indicated that GhGRFs are ideal target genes with significant potential for improving the molecular structure of cotton.