Molecular cloning, characterization, and expression analysis of two class II chitinase genes from the strawberry plant

Abstract

Plant chitinases are pathogenesis-related proteins, which are believed to be involved in plant defense responses to pathogen infection. We have cloned, sequenced, partially characterized, and analyzed the expression patterns of two strawberry class II chitinase genes, designated FaChi2-1 and FaChi2-2. Nucleotide sequence data indicated that FaChi2-1 and FaChi2-2 contain two and three exons, respectively. The splice junctions in these genes were confirmed by sequence analyses of corresponding cDNA clones. The translation products of both genes showed high degrees of homology to other class II chitinases. Genomic Southern blot analysis indicated that each chitinase gene represents a multigene family. The transcription start sites of the two genes were determined by primer extension analysis. Reverse transcriptase-polymerase chain reaction analysis indicated that both genes are constitutively expressed in strawberry leaves. Expression of these genes in strawberry plants inoculated with Colletotrichum fragariae or Colletotrichum acutatum, two important strawberry fungal pathogens, was examined at different time points using real-time PCR. FaChi2-1 showed a rapid induction, which occurred within 2–6 h post-inoculation. Induction of FaChi2-2 occurred slower, at 24–48 h post-inoculation.