AUTHOR=Haxim Yakupjan , Kahar Gulnaz , Zhang Xuechun , Si Yu , Waheed Abdul , Liu Xiaojie , Wen Xuejing , Li Xiaoshuang , Zhang Daoyuan 

TITLE=Genome-wide characterization of the chitinase gene family in wild apple (Malus sieversii) and domesticated apple (Malus domestica) reveals its role in resistance to Valsa mali

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.1007936

DOI=10.3389/fpls.2022.1007936

ISSN=1664-462X

ABSTRACT=<p>Chitinases are responsible for catalyzing the hydrolysis of chitin and contribute to plant defense against fungal pathogens by degrading fungal chitin. In this study, genome-wide identification of the chitinase gene family of wild apple (<italic>Malus sieversii</italic>) and domesticated apple (<italic>Malus domestica</italic>) was conducted, and the expression profile was analyzed in response to <italic>Valsa mali</italic> infection. A total of 36 and 47 chitinase genes belonging to the glycosyl hydrolase 18 (GH18) and 19 (GH19) families were identified in the genomes of <italic>M. sieversii</italic> and <italic>M. domestica</italic>, respectively. These genes were classified into five classes based on their phylogenetic relationships and conserved catalytic domains. The genes were randomly distributed on the chromosomes and exhibited expansion by tandem and segmental duplication. Eight of the 36 <italic>MsChi</italic> genes and 17 of the 47 <italic>MdChi</italic> genes were differentially expressed in response to <italic>V. mali</italic> inoculation. In particular, <italic>MsChi35</italic> and its ortholog <italic>MdChi41</italic>, a class IV chitinase, were constitutively expressed at high levels in <italic>M. sieversii</italic> and domesticated apple, respectively, and may play a crucial role in the defense response against <italic>V. mali</italic>. These results improve knowledge of the chitinase gene family in apple species and provide a foundation for further studies of fungal disease prevention in apple.</p>