Identification and expression analysis of chitinase genes in Zizania latifolia in response to abiotic stress

Zizania latifolia is the second-most cultivated aquatic vegetable in China, because of its nutritional and health-giving properties, and its cultivation is of considerable economic importance. Plant chitinases, as members of the glycoside hydrolase family, are considered primarily to be proteins involved in plant response to biotic and abiotic stresses, although they are also involved in many other physiological and morphological processes. In order to analyze the expression of chitinase genes under abiotic stress conditions in Z. latifolia and to better understand the functionality of these genes in this plant, we carried out a BLAST search of the Z. latifolia genome database and phylogenetic analysis based on the neighbor-joining method. Eleven chitinase genes were identified (ZlChi1-11) and classified into the chitinase classes I, II and IV. Seedlings were exposed to various abiotic stresses including salt, heat, cold, drought and the stress hormone abscisic acid (ABA) and expression patterns of all 11 chitinase genes in Z. latifolia were determined by quantitative reverse-transcription PCR. The results showed that most ZlChis were differentially expressed under abiotic stress conditions. The expression patterns indicated that most ZlChis responded to abiotic stresses within 6 h, although some ZlChis reached peak expression at 12 h or 18 h of abiotic stress treatment. Expression of ZlChi2 and ZlChi5 was upregulated under each of the stress treatments, while that of ZlChi10 or ZlChi11 was not detected under any conditions. This is the first report of expression analysis of all members of the glycoside hydrolase family 19 genes in Z. latifolia under abiotic stress, which provides basic information and insights into the putative roles of these genes in response to abiotic stress. The results of this study should serve as the basis for further functional characterization of these gene families in Zizania latifolia and related members of the Poaceae.