Isolation and characterization of an isoamylase gene from rye

Genomic DNA and cDNA sequences of an isoamylase gene were isolated and characterized from the rye genome. The full-lengths of the rye isoamylase gene are 7351 bp for genomic DNA and 2364 bp for cDNA. There are 18 exons and 17 introns in the genomic sequence, which shares a similar organization with homologous genes from Aegilops tauschii, maize, rice and Arabidopsis. Exon regions of rye and other plant isoamylase genes are more conserved than the introns. High sequence similarity (> 95%) was observed in mature proteins of isoamylase genes originating from rye, Ae. tauschii, wheat and barley. The transcript profile revealed that rye isoamylase is mainly expressed in the seed endosperm with a maximum level at the middle developmental stage (15 DPA). A phylogenetic tree based on the deduced aa sequences of mature proteins from rye and other plant isoamylases indicated that rye isoamylase is more closely related to Ae. tauschii wDBE1 and wheat iso1. This is the first report on identification and characterization of the isoamylase gene from rye, making it possible to explore the roles of this enzyme for amylopectin development in rye and triticale.