Genome-Wide Identification and Expression Analyses of the Chitinases under Cold and Osmotic stress in Ammopiptanthus nanus.

Cao Cao,Feng Feng,Zhang Zhang,Zhou Zhou,Wang Wang,Shi Shi,Li Li,Gao Gao

doi:10.3390/genes10060472

Abstract

Chitinase is a kind of hydrolase with chitin as a substrate and is proposed to play an essential role in plant defense system by functioning against fungal pathogens through degrading chitin. Recent studies indicated chitinase is also involved in abiotic stress response in plants, helping plants to survive in stressful environments. A. nanus, a rare evergreen broad-leaved shrub distrusted in deserts in Central Asia, exhibits a high level of tolerance to drought and low temperature stresses. To identify the chitinase gene involved in drought and low temperature responses in A. nanus, we performed genome-wide identification, classification, sequence alignment, and spatio-temporal gene expression analysis of the chitinases in A. nanus under osmotic and low temperature stress. A total of 32 chitinase genes belonging to glycosyl hydrolase 18 (GH18) and GH19 families were identified from A. nanus. Class III chitinases appear to be amplified quantitatively in A. nanus, and their genes carry less introns, indicating their involvement in stress response in A. nanus. The expression level of the majority of chitinases varied in leaves, stems, and roots, and regulated under environmental stress. Some chitinases, such as EVM0022783, EVM0020238, and EVM0003645, are strongly induced by low temperature and osmotic stress, and the MYC/ICE1 (inducer of CBF expression 1) binding sites in promoter regions may mediate the induction of these chitinases under stress. These chitinases might play key roles in the tolerance to these abiotic stress in A. nanus and have potential for biotechnological applications. This study provided important data for understanding the biological functions of chitinases in A. nanus.

Highlights

Chitinase is a type of hydrolase with chitin as a substrate, and chitin is a glycopolymer of β-1,4-linked N-acetyl-D-glucosamine
A total of 32 chitinase genes were identified from the genome sequence of A. nanus, and out of these chitinases, 24 were classified into the glycosyl hydrolase 18 (GH18) subfamily, and 8 into the GH19 subfamily (Table 1 and Figure 1)
The 32 predicted chitinases range in length from 119 to 1027 amino acid residues, with 27 chitinase genes falling in length range from 245 to 441 amino acid residues

Summary

Introduction

Chitinase is a type of hydrolase with chitin as a substrate, and chitin is a glycopolymer of β-1,4-linked N-acetyl-D-glucosamine. Plant chitinase catalyzes the hydrolysis of β-1, 4 glycosidic bonds in chitin in fungal cell walls and releases chitin. As one of the functional families of pathogenesis-related proteins (PRs), chitinases play key roles in the plant defense system by protecting plants from chitin-containing pathogens such as fungi [8], and are considered important target genes for crop improvement [1]. The endogenous substrate of plant chitinase is not determined, several chitinases are suggested to cleave arabinogalactan proteins (AGPs) [9] and N-acetylglucosamine-containing glycoproteins in the plant cell walls [10], and released oligosaccharides that might act as signal molecules triggering a defense response in plants

Methods

Results

Discussion

Conclusion