45. Mutants affecting storage protein in rice seed

1)Plant Breeding Lyboratory, Faculty of Agriculture, Kyushu University, Fukuoka, 812

Rice storage proteins in the starchy endosperm can be fractionated by SDS-PAGE into more than 11 components, and they are grouped into seven categories each with a different molecular mass, i.e., 57, 37-39, 26,22-23, 16, 13 and 10 kDa polypeptides. These storage proteins are mainly accumulated in subcellular proteinaceous particles called protein bodies (PB). Tanaka et al. (1980) isolated two types of protein bodies in the starchy endosperm of rice, PB-I and PB-II, which are characterized from each other by difference in size, density and the polypeptide composition. PB-I is spherical and 1-2um in diameter with a lamellar structure and contains 10,13 and 16 kDa polypeptides which are alcohol soluble proteins (prolamin), while PB-II is 23 um in diameter and stained homogeneously by osmium tetroxide with no lamellar tructure and contains 22-23 and 37-39 kDa polypeptides which are acid soluble proteins (glutelin), and also contains 26 kDa polypeptide (globulin). The 57 kDa polypeptide is a possible percursor of the glutelin (22-23 kDa and 37-39 kDa polypeptide) (Yamagata et al. 1982, 1986), but its accumulation site is unknown.

We analyzed the storage proteins of the mutant lines induced by the fertilize egg-cell treatment with MNU, by using SDS-PAGE, and obtained four types of mutants showing 13 kDa polypeptide less, 10 kDa polypeptide much, 10 kDa polypeptide less and 57 kDa polypeptide much, respectively (Fig. 1). Among them, CM 21 and CM 1834 were characterized by a decrease in the amount of smaller component of 13 kDa polypeptide, and CM 1834 showed an increase in the amount of 10 and 16 kDa polypeptides as compared to Kinmaze. These two mutants had an increased glutelin content. The decrease in the small component of 13 kDa polypeptide of CM 21 was controlled by a single recessive gene. CM 1675 had a decreasd amount of 10 Da, the large component of 13 kDa and 16 kDa polypeptides instead of increased amount of small component of 13 kDa polypeptide. CM 1987 contained a considerably increased amount of 57 kDa polypeptide and a reduced amount of 22-23 and 37-39 kDa polypeptides. This was controlled by a single recessive gene.

Fig. 1. SDS-PAGE analysis of rice storage protein from four types of mutants. KINMAZE (original variety). CM 21 (decreased amount of 13 kDa-beta polypeptide). CM 1675 (decreased amount of 10 kDa, 13 kDa-alpha and 16 kDa polypeptides). CM 1787 (increased amount of 57 kDa polypeptide). CM 1834 (increased amount of 10 kDa and 16 kDa polypeptides and decreased amount of 13 kDa-beta polypeptide).

Tanaka, K., T. Sugimoto, M. Ogawa and Z. Kasai, 1980. Isolation and characterization of two types of protein bodies in the rice endosperm. Agric. Biol. Chem. 44: 1633-1639.

Yamagata, H., T. Sugimoto, K. Tanaka and Z. Kasai, 1982. Biosynthesis of storage protein in developing rice seeds. Plant Physiol. 70: 1094-1100.

Yamagata, H. and K. Tanaka, 1986. The site of synthesis and accumulation of rice storage proteins. Plant Cell Physiol. 27: 135-145.