Identification and expression analysis of chitinase genes related to biotic stress resistance in Brassica

Brassica is a very important vegetable group because of its contribution to human nutrition and consequent economic benefits. However, biotic stress is a major concern for these crops and molecular biology techniques offer the most efficient of approaches to address this concern. Chitinase is an important biotic stress resistance-related gene. We identified three genes designated as Brassica chitinase like protein (BrCLP1), BrCLP2 and BrCLP3 from a full-length cDNA library of Brassica rapa cv. Osome. Sequence analysis of these genes confirmed that BrCLP1 was a class IV chitinase, and BrCLP2 and BrCLP3 were class VII chitinases. Also, these genes showed a high degree of homology with other biotic stress resistance-related plant chitinases. In expression analysis, organ-specific expression of all three genes was high except BrCLP1 in all the organs tested and BrCLP2 showed the highest expression compared to the other genes in flower buds. All these genes also showed expression during all developmental growth stages of Chinese cabbage. In addition, BrCLP1 was up-regulated with certain time of infection by Pectobacterium carotovorum subsp. carotovorum in Chinese cabbage plants during microarray expression analysis. On the other hand, expression of BrCLP2 and BrCLP3 were increased after 6 h post inoculation (hpi) but decreased from 12 hpi. All these data suggest that these three chitinase genes may be involved in plant resistance against biotic stresses.