水稻和拟南芥中几丁质酶的分析.pdf

Journal of Genetics and Genomics (Formerly Acta Genetica Sinica) February 2007, 34(2): 138-150 Research Article Chitinases in Oryza sativa ssp. japonica and Arabidopsis thaliana Fenghua Xu, Chengming Fan, Yueqiu He① Key Laboratory of Plant Pathology of the Ministry of Education, Yunnan Agricultural University, Kunming 650201, China Abstract: Chitinases (EC4), found in a wide range of organisms, catalyze the hydrolysis of chitin and play a major role in defense mechanisms against fungal pathogens. The alignment and typical domains were analyzed using basic local alignment search tool (BLAST) and simple modular architecture research tool (SMART), respectively. On the basis of the annotations of rice (Oryza sativa L.) and Arabidopsis genomic sequences and using the bio-software SignalP3.0, TMHMM2.0, TargetP1.1, and big-Pi Predic- tor, 25 out of 37 and 16 out of 24 open reading frames (ORFs) with chitinase activity from rice and Arabidopsis , respectively, were predicted to have signal peptides (SPs), which have an average of 24.8 amino acids at the N-terminal region. Some of the chitinases were secreted extracellularly, whereas some were located in the vacuole. The phylogenic relationship was analyzed with 61 ORFs and 25 known chitinases and they were classified into 6 clusters using Clustal X and MEGA3.1. This classification is not com- pletely consistent when compared with the traditional system that classifies the chitinases into 7 classes. The frequency of distribu- tion of amino acid residues was distinct in different clusters. The contents of alanine, glycine, serine, and leucine were very high in each cluster, whereas the contents of methionine, histidine, tryptophan, and cysteine were lower than 20%. Each cluster had distinct amino acid characteristics. Alanine