Molecular characterization of a gene encoding a cystatin expressed in the stems of American chestnut (Castanea dentata)

A cDNA clone with similarity to genes encoding cystatin was recently isolated from a cDNA library created using mRNA extracted from stem tissues of Castanea dentata (Marsh.) Borkh. (CASde:Pic1). All of the requisite motifs for inhibitory activity were found upon examination of the deduced amino acid sequence. Reverse transcription-polymerase chain reaction was used to detect the cystatin transcript in healthy stem, leaf and seed tissues, as well as in diseased tissues. Gene fragments encoding this putative cystatin were cloned from American and Chinese (Castanea mollissima Blume) chestnuts and a comparison of these sequences revealed significant differences within the intron, including deletions and alterations in restriction-enzyme sites. The long-term goal of this study is to determine whether the cystatin allele in Chinese chestnut correlates to a resistance gene and, if so, if this allele could be used to enhance resistance in American chestnut.