Genome-wide analysis of the CaHsp20 gene family in pepper: comprehensive sequence and expression profile analysis under heat stress

Meng Guo,Shu-Bin Wang,Hu Wang,Jin-Ping Lu,Ming-Hui Lu,Yu-Fei Zhai,Jin-Hong Liu,Zhen-Hui Gong

doi:10.3389/fpls.2015.00806

Abstract

The Hsp20 genes are present in all plant species and play important roles in alleviating heat stress and enhancing plant thermotolerance by preventing the irreversible aggregation of denaturing proteins. However, very little is known about the CaHsp20 gene family in pepper (Capsicum annuum L.), an important vegetable crop with character of temperate but thermosensitive. In this study, a total of 35 putative pepper Hsp20 genes (CaHsp20s) were identified and renamed on the basis of their molecular weight, and then their gene structure, genome location, gene duplication, phylogenetic relationship, and interaction network were also analyzed. The expression patterns of CaHsp20 genes in four different tissues (root, stem, leaf, and flower) from the thermotolerant line R9 under heat stress condition were measured using semi-quantitative RT-PCR. The transcripts of most CaHsp20 genes maintained a low level in all of the four tissues under normal temperature condition, but were highly induced by heat stress, while the expression of CaHsp16.6b, 16.7, and 23.8 were only detected in specific tissues and were not so sensitive to heat stress like other CaHsp20 genes. In addition, compared to those in thermotolerant line R9, the expression peak of most CaHsp20 genes in thermosensitive line B6 under heat stress was hysteretic, and several CaHsp20 genes (CaHsp16.4, 18.2a, 18.7, 21.2, 22.0, 25.8, and 25.9) showed higher expression levels in both line B6 and R9. These data suggest that the CaHsp20 genes may be involved in heat stress and defense responses in pepper, which provides the basis for further functional analyses of CaHsp20s in the formation of pepper acquired thermotoleance.

Highlights

As the sessile organisms, plants cannot escape the extreme environment conditions, including biotic and abiotic stresses, such as pests and pathogens, drought, salinity, cold, heat, and heavy metal stresses (Wang et al, 2003; Mittler, 2006; Mittler et al, 2012)
Identification and Analysis of CaHsp20 Gene Family Members in Pepper A total of 41 sequences of Hsp20 gene were gotten from PGD by Hidden Markov Model (HMM) analysis, out of which 35 were annotated as being pepper Hsp20 genes based on the confirmation of Pfam and SMART scans, and sequences without a complete domain (CA09g15370, CA12g15460, and CA03g18690) and sequences whose molecular weight out of the range of Hsp20s (CA08g09970, CA04g23450, and CA00g46140) were removed
The 35 CaHsp20 genes were named according to their molecular weight (Table 1)

Summary

Introduction

Plants cannot escape the extreme environment conditions, including biotic and abiotic stresses, such as pests and pathogens, drought, salinity, cold, heat, and heavy metal stresses (Wang et al, 2003; Mittler, 2006; Mittler et al, 2012). Among all the five conserved families, Hsp20s, a group of small heat shock proteins (sHsps) with molecular size ranging from 15 to 42 kDa, are the most prevalent and abundant family induced by HS in many higher plants. They can function as molecular chaperone without ATP to maintain the stability of proteins, which suggest that Hsp20s may play a vital role during the formation of plant acquired thermotolerance (Vierling, 1991; Sun et al, 2002; Wang et al, 2004; Waters, 2013; Haslbeck and Vierling, 2015)

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Discussion

Conclusion