Abstract
This research aims to reveal the function of isoamylase (ISA) and pullulanase (PUL) in rice endosperm. We have already established that ISA1-ISA2 hetero- and ISA1 homo-complexes co-exist in rice endosperm while there is only ISA1-ISA2 hetero-complex in potato tuber. To suppress the OsISA1 and OsISA2 by the RNAi technology, the calli of Kinmaze and rice PUL mutant were transformed.. The ISA1 suppressed lines lost the ISA activity in the endosperm and displayed the phytoglycogen-storage phenotype. The ISA2 suppressed lines had only the ISA1 homo-complex activity but no substantial phenotypic changes were observed, suggesting a considerable overlap in functions between ISA1 homo-complex and ISA1-ISA2 hetero-complex and PUL. These results sharply contrast with the previous studies showing that the reduction of ISA2 expression results in sugary phenotype in Arabidopsis leaves and potato tuber. This suggests that the function of a considerable overlap in functions between ISA1-homo and ISA1-ISA2 hetero-complexes and PUL.
