Characteristic Analysis and Homology Alignment of EST-SNPs and Candidate Genes for Chestnut Blight Resistance of Castanea mollissima

Unigene sequences and EST-SNPs derived from Castanea mollissima were downloaded from the Fagaceae Genomics database (www.fagaceae.org).The EST-SNP frequency in those unigenes was 1 SNP per 251 bp.For substitution types of those EST-SNPs,C-T substitution was the most frequent mutation type,accounting for 31.84% of all EST-SNPs,while C-G substitution occurred most rarely,accounting for only 5.76% of all EST-SNPs.The ratio of transition to transversion was 1.74 :1.Gene ontology for 211 differentially expressed genes in chestnut blight fungus (Cryphonectria parasitica) infected vs healthy stem tissues of Castanea mollissima were investigated.Except for other cellular and metabolic processes,protein meta-bolism,response to stress,and response to abiotic or biotic stimulus were among the most represented biological process categories.Many transmembrane domains,signal peptides,coiled coil regions,and Pkinase related domains were found from analysis of protein sequences of the 211 differentially expressed genes.Using TBLASTX,the 211 differentially expressed genes were compared to all unigene sequences of Castanea mollissima.The EST-SNPs located on the homologous unigene sequences were summarized and resulted in a total of 3023 EST-SNPs.These EST-SNP markers provide insights into the studies of population genomics and association mapping for chestnut blight resistance in Castanea mollissima.