Characterization of bHLH/HLH genes that are involved in brassinosteroid (BR) signaling in fiber development of cotton (Gossypium hirsutum)

Rui Lu,Xue-Bao Li,Ying-Li Wei,Dong Liu,Jiao Zhang,Yao Wang

doi:10.1186/s12870-018-1523-y

Abstract

BackgroundBasic helix-loop-helix/helix-loop-helix (bHLH/HLH) transcription factors play important roles in plant development. Many reports have suggested that bHLH/HLH proteins participate in brassinosteroid (BR) hormone signaling pathways to promote cell elongation. Cotton fibers are single-cells and derived from seed surface. To explore the roles of bHLH/HLH proteins in cotton fiber development progress by modulating BR signaling pathway, we performed a systematic analysis of the bHLH/HLH gene family in upland cotton (Gossypium hirsutum) genome.ResultsIn this study, we identified 437 bHLH/HLH genes in upland cotton (G. hirsutum) genome. Phylogenetic analysis revealed that GhbHLH/HLH proteins were split into twenty six clades in the tree. These GhbHLH/HLH genes are distributed unevenly in different chromosomes of cotton genome. Segmental duplication is the predominant gene duplication event and the major contributor for amplification of GhbHLH/HLH gene family. The GhbHLH/HLHs within the same group have conserved exon/intron pattern and their encoding proteins show conserved motif composition. Based on transcriptome data, we identified 77 GhbHLH/HLH candidates that are expressed at relatively high levels in cotton fibers. As adding exogenous BR (brassinolide, BL) or brassinazole (Brz, a BR biosynthesis inhibitor), expressions of these GhbHLH/HLH genes were up-regulated or down-regulated in cotton fibers. Furthermore, overexpression of GhbHLH282 (one of the BR-response genes) in Arabidopsis not only promoted the plant growth, but also changed plant response to BR signaling.ConclusionCollectively, these data suggested that these GhbHLH/HLH genes may participate in BR signaling transduction during cotton fiber development. Thus, our results may provide a valuable reference data as the basis for further studying the roles of these bHLH/HLH genes in cotton fiber development.

Highlights

Basic helix-loop-helix/helix-loop-helix transcription factors play important roles in plant development
Characterization of cotton bHLH/HLH transcription factors To identify the bHLH/HLH transcription factor genes in upland cotton (G. hirsutum) genome, all published bHLH/ HLH gene sequences of Arabidopsis and rice were employed as queries to perform homologous blast searches against the cotton genome database [32]
Since there was no uniform annotation for the GhbHLH/HLH genes, the bHLH/HLH genes are named as GhbHLH001 to GhbHLH437 according to their chromosome locations

Summary

Introduction

Basic helix-loop-helix/helix-loop-helix (bHLH/HLH) transcription factors play important roles in plant development. Many reports have suggested that bHLH/HLH proteins participate in brassinosteroid (BR) hormone signaling pathways to promote cell elongation. Cotton fibers are single-cells and derived from seed surface. To explore the roles of bHLH/HLH proteins in cotton fiber development progress by modulating BR signaling pathway, we performed a systematic analysis of the bHLH/HLH gene family in upland cotton (Gossypium hirsutum) genome. One of the most important economic crops, supplies the largest number of natural fibers in the textile market around the world. Upland cotton (G. hirsutum) accounts for the largest planting area among the varieties of cotton crops and provides most of the valuable fibers needed by modern textile industry. Fiber development is divided into four overlapping stages, fiber initiation, elongation, secondary cell wall thickening and maturity [2].

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Conclusion