16. Environmental control of gene expression in endosperm mutants of rice

Kazutoshi Okuno

Hokuriku National Agricultural Experiment Station, Joetsu, Niigata, 943-01 Japan

The temperatures during the development of rice endosperm affect the amylose content and distribution of α-1,4 chains of amylopectin in starch granules of glutinous and nonglutinous isogenic lines (Asaoka et al. 1984, 1985). The present study was undertaken to determine the effect of temperature on phenotypic expression of du and ae mutant genes reported by the authors recently (Okuno and Yano 1984).

Starch granules were isolated from polished grains of low (du) and high amylose (ae) mutants and their original cultivar grown under different environmental conditions. The starch was analyzed by gel filtration on Toyopearl HW55SF and HW50SF columns of starch components after debranching with Pseudomonas isoamylase.

The amylose content (Fr.I) of three du mutants grown at Sendai were 7.1, 10.8 and 11.4%, respectively, as compared with 16.0% in the normal (Table 1). The amylose content of these mutants grown at Kurashiki was about 60% of those at Sendai. The du mutants grown at Kurashiki possessed larger amount of Fr.II (Longer chains of amylopectin) than those at Sendai, accounting for the reduced amylose content. The Fr.III/Fr.II ratios differed for du mutants at Sendai and Kurashiki, suggesting changes in the distribution of α-1,4 chains of amylopectin.

Furthermore, the amylose content in ae mutant grown at Joetsu was about 70% of that at Tsukuba. A slight increase in the content of Fr.II was found in ae mutant and the normal lines at Joetsu, as compared with those of Tsukuba. The Fr.III/Fr.II ratios did not differ between the materials grown at Joetsu and Tsukuba, indicating that the distribution of α-1,4 chains of amylopectin remained unchanged in those materials.

The changes in the amylose content and distribution of α-1,4 chains of amylopectin were closely correlated with the daily mean temperature up to 20 days after heading of the mutant and normal lines. These results agree with those obtained in glutinous and ordinary isogenic lines of Taichung 65 (Asoka et al. 1985).

References

Asaoka, M., K. Okuno, Y. Sugimoto, J. Kawakami and H. Fuwa, 1984. The effect of envirnomental temperature during development of rice plants (Oryza sativa L.) on some properties of endosperm starch. Starke 36: 189-193.

Asaoka, M., K. Okuno and H. Fuwa, 1985. Effect of environmental temperature at milky stage on amylose content and fine structure of amylopectin on waxy and nonwaxy endosperm starches of rice (Oryza sativa L.). Agric. Biol. Chem. 49: 373-379.

Okuno, K. and M. Yano, 1984. Mutant genes controlling starch synthesis in rice endosperms. Rice Genetics Newsletter 1: 112-113.