Genome-Wide Identification and Characterization of Melon bHLH Transcription Factors in Regulation of Fruit Development.

Chao Tan,Xue Wang,Agula Hasi,Selinge Bai,Ming Ma,Huilei Qiao,Yunyun Tian

doi:10.3390/plants10122721

Chao Tan, Xue Wang + Show 5 more

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https://doi.org/10.3390/plants10122721

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Abstract

The basic helix-loop-helix (bHLH) transcription factor family is one of the largest transcription factor families in plants and plays crucial roles in plant development. Melon is an important horticultural plant as well as an attractive model plant for studying fruit ripening. However, the bHLH gene family of melon has not yet been identified, and its functions in fruit growth and ripening are seldom researched. In this study, 118 bHLH genes were identified in the melon genome. These CmbHLH genes were unevenly distributed on chromosomes 1 to 12, and five CmbHLHs were tandem repeat on chromosomes 4 and 8. There were 13 intron distribution patterns among the CmbHLH genes. Phylogenetic analysis illustrated that these CmbHLHs could be classified into 16 subfamilies. Expression patterns of the CmbHLH genes were studied using transcriptome data. Tissue specific expression of the CmbHLH32 gene was analysed by quantitative RT-PCR. The results showed that the CmbHLH32 gene was highly expressed in female flower and early developmental stage fruit. Transgenic melon lines overexpressing CmbHLH32 were generated, and overexpression of CmbHLH32 resulted in early fruit ripening compared to wild type. The CmbHLH transcription factor family was identified and analysed for the first time in melon, and overexpression of CmbHLH32 affected the ripening time of melon fruit. These findings laid a foundation for further study on the role of bHLH family members in the growth and development of melon.

Highlights

Transcription factors (TFs) play important roles in regulating plant growth, development, stress response and signal transduction [1,2,3,4]
After that 214 sequences were reserved and submitted to CDD domain search; 159 sequences were found with a Basic helix-loop-helix (bHLH) conserved domain above the minimum domain hit, and the redundant sequences of the 159 proteins were removed
This study was focused on the identification of the melon bHLH gene family and the function of bHLH genes in fruit growth and ripening

Summary

Introduction

Transcription factors (TFs) play important roles in regulating plant growth, development, stress response and signal transduction [1,2,3,4]. Basic helix-loop-helix (bHLH) TFs is one of the largest TF superfamilies in plant [5]. Studies on the bHLH gene family in various species will increase our understanding of their evolution and functions. Plant bHLH genes are characterized by a basic helix-loop-helix domain which is highly conserved in evolution [11]. The bHLH domain contains 50–60 amino acids and can be separated into two regions: the region at the N-terminal end is a DNA binding domain, comprised of approximately 13–17 amino acids [5]; the C-terminal end is an HLH domain, containing two amphipathic α-helices connected by a loop region with variable length, which helps to form a dimerization domain, and allows the formation of homo or heterodimeric complexes [12]. With regard to the bHLH protein domain, 19 amino acids are conserved and functional for DNA binding or dimerization formation. A highly conserved HER motif (His 5-Glu 9-Arg 13) is considered important for binding to specific

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