Poster: Plant Pathogen/Symbiont Interactions

Abs # 771: Cloning, characterization, and expression analysis of two class II chitinase genes from the strawberry plant

Presenter:	Anwar, Khan A., akhan1@lsu.edu
Authors	Anwar, Khan A. (A)   Zhang, Yuhua  (A)   Shih, Ding S. (A)
Affiliations:	(A): Louisiana State University

Chitinases are pathogensis-related proteins, which are believed to be involved in plants' defense against pathogen infections. We have cloned, sequenced, partially characterized, and analyzed the expression of two strawberry class II chitinase genes, designed FaChi2-1 and FaChi2-2. Nucleotide sequence data indicated that FaChi2-1 and FaChi2-2 consist of two and three exons, respectively. The locations of the splice junctions in the two genes were confirmed by sequence analysis of cDNA clones of these genes. The translation products of both genes show high degrees of homology to other class II chitinases. Southern blot analysis revealed multiple hybridization bands from each gene, indicating each represents a small multigene family. The transcription start sites of the two genes were determined by primer extension analysis. Results from reverse transcriptase-polymerase chain reaction (RT-PCR) analysis indicated that both genes are constitutively expressed in strawberry leaves. Using real-time PCR, the expression of the two genes in plants inoculated with Colletotrichum fragariae or Colletotrichum acutatum , two most important strawberry pathogens, was examined at different time points post-inoculation. FaChi2-1 showed a rapid response to infection, with induction occurring within 2 h post-inoculation. Induction of FaChi2-2 was slower, occurring at 24-48 h post-inoculation. The total chitinase enzyme activities of the inoculated plants were also examined. Both Colletotrichum species caused an approximate five-fold increase of the enzyme activity at 24 h post-inoculation.