Functional diversity of isoamylase oligomers: the ISA1 homo-oligomer is essential for amylopectin biosynthesis in rice endosperm.

摘要: Rice (Oryza sativa) endosperm has two isoamylase (ISA) oligomers, ISA1 homo-oligomer and ISA1-ISA2 hetero-oligomer. To examine their contribution to starch synthesis, expression of the or ISA2 gene was differently regulated in various transgenic plants. Although suppression caused have only homo-oligomer, no significant effects were detected on phenotypes. In contrast, overexpression led having hetero-oligomer, synthesis drastically impaired, both quantitatively qualitatively, because devoid typical features, such as thermal x-ray diffraction properties, water-soluble highly branched maltodextrins accumulated. overexpressed line, about 60% 70% hetero-oligomer bound starch, while ISA homo- hetero-oligomers from wild type mostly present soluble form at early milking stage endosperm. Detailed analysis relative amounts lines also us conclusion that is essential, but not oligomer, for production rice The proteins shown determine ratio oligomers stoichiometry ISAs It noted when compared with all leaf potato (Solanum tuberosum) tuber much more stable 40°C. This study provides substantial data structural functional diversity between plant tissues species.