Expression of α-Amylase Isoforms and the RAmy1A Gene in Rice (Oryza sativa L.) during Seed Germination, and its Relationship with Coleoptile Length in Submerged Soil

Abstract

A significant difference in the seed germinability was observed between the two rice cultivars, 'Nipponbare' and 'Suweon 287', under anoxia (i.e., during germination in submerged soil at 18°C), althouth little difference was seen under aerobic (in air) or hypoxic (in water) conditions. The number of α-amylase isoforms synthesized in germinating seeds was inversely proportional to the O₂ concentrations at the early gemination stage. The formation of isoform B was promoted by oxygen supply, while isoform H was undetectable if the seeds were unable to germinate. The activity of isoform H was highly correlated with the coleoptile length in the submerged soil at 18°C, indicating that isoform H is a critical factor for seed germination under anoxia. The expression of the rice α-amylase RAmy1A gene was repressed when the seeds germinated under hypoxia or anoxia. The interations between oxygen stress, gibberelin, and carbon metabolites on the expression of α-amylase in rice are discussed.