Genome-wide Analysis of Basic Helix-Loop-Helix Family Genes and Expression Analysis in Response to Drought and Salt Stresses in Hibiscus hamabo Sieb. et Zucc.

Longjie Ni,Zhiquan Wang,Zekai Fu,Dina Liu,Yunlong Yin,Chunsun Gu,Huogen Li

doi:10.3390/ijms22168748

Abstract

The basic helix-loop-helix (bHLH) family of transcription factors is one of the most significant and biggest in plants. It is involved in the regulation of both growth and development, as well as stress response. Numerous members of the bHLH family have been found and characterized in woody plants in recent years. However, no systematic study of the bHLH gene family has been published for Hibiscus hamabo Sieb. et Zucc. In this research, we identified 162 bHLH proteins (HhbHLHs) from the genomic and transcriptomic datasets of H. hamabo, which were phylogenetically divided into 19 subfamilies. According to a gene structural study, the number of exon-introns in HhbHLHs varied between zero and seventeen. MEME research revealed that the majority of HhbHLH proteins contained three conserved motifs, 1, 4, and 5. The examination of promoter cis-elements revealed that the majority of HhbHLH genes had several cis-elements involved in plant growth and development and abiotic stress responses. In addition, the overexpression of HhbHLH2 increased salt and drought stress tolerance in Arabidopsis.

Highlights

Transcription factors (TFs) are protein molecules with distinct structural and functional characteristics that influence gene expression
According to the magnitude of the Ks value, we found that the HhbHLH gene family whole-genome duplication (WGD)/segmental events occurred in different periods; some occurred in a distant period (Ks > 1) and others occurred in a relatively recent period (Ks < 0) (Table S4)
The results show that genes responsive to light, low temperature, gibberellin, MeJA, drought stress, wounds, and MYB binding sites involved in drought and other elements related to stress response were abundantly enriched in the promoter region of the HhbHLH gene

Summary

Introduction

Transcription factors (TFs) are protein molecules with distinct structural and functional characteristics that influence gene expression. The basic helix–loop–helix (bHLH) transcription factor family is the second biggest protein family found in plants [2]. It is characterized by a conserved domain consisting of 40–60 amino acids, which consists of two parts: the basic region and the HLH region. The basic region is located at the N-terminus and is composed of 13–17 basic amino acids, which are used as the DNA binding region to identify and bind DNA promoters and target genes. The HLH region is found at the C-terminus of the bHLH domain and consists of two parental helixes bound by relatively distributed (length and primary sequence) loop regions that promote protein interactions [3,4,5]. The maize R gene, which is required for anthocyanin production, was the first member of the bHLH family to be identified [6]

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Discussion

Conclusion