RT-qPCR analysis of genes associated with chestnut blight in susceptible American and resistant Chinese chestnut trees

American chestnut (Castanea dentata) is highly susceptible to infection caused by the necrotrophic fungus, Cryphonectria parasitica. Closely related Chinese chestnut (C. mollissima) exhibits a natural resistance to blight. Genes commonly induced during plant defense response to infection, including genes for b-1,3-glucanase, cinnamyl alcohol dehydrogenase (CAD) and laccase, were preliminarily identified as differentially expressed between Chinese and American chestnut using suppression subtractive hybridization (SSH). Full-length cDNA sequences of these genes have been identified in both chestnut species using the Fagaceae genomic website (http://www.fagaceae.org/home). Genes from the two species are very similar in DNA sequence, therefore it is likely the expression patterns of specific genes is important to conferring the blight-resistance in Chinese chestnut. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) was used to confirm and quantify differential gene expression between American and Chinese chestnut stem tissues. Results indicate there is significantly higher expression of some defense related genes in stems of Chinese chestnut than in American chestnut. Laccase, for example, had several hundred fold higher expression in Chinese chestnut seedlings. Genes more highly expressed in Chinese chestnut would be good candidates for use in genetic modification of American chestnut to determine if they can enhance resistance to chestnut blight.