Rice glutelin is composed of two major subunits, an acidic subunit with molecular mass of 40kD and a basic subunit with molecular mass of 20kD (Tanaka et al., 1980). Many researchers have reported the diversity of glutelin acidic subunit (Jahan et al., 2003, Kagawa et al., 1988, Satoh et al., 1990) however the diversity of glutelin basic subunit has not been reported. This report deals with the genetic diversity of glutelin basic subunit in Myanmar local rice cultivars.

A total of 367 local rice cultivars collected from seven distinct regions of Myanmar were analyzed by SDS-PAGE and IEF electrophoresis. Glutelin was extracted with 1% lactic acid solution and SDS-PAGE and IEF were carried out according to the method of Uemura et al. (1996) with slightly modified. Kinmaze (japonica) and IR36 (indica) cultivars were used as control.

The basic subunits are further separated into 23kD, 22.5kD and 22kD polypeptides designated as Beta-1, Beta-2 and Beta-3 bands, respectively, by SDS-PAGE (Uemura et al., 1996). The staining intensity of individual bands, Beta-1, Beta-2 and Beta-3 subunits in Kinmaze were identical to those of IR36 (Fig. 1, lane 1 and 2). Variations for glutelin basic subunits were observed and classified into seven types, that is, three types for Beta-1, 2 types for Beta-2 and 2 types for Beta-3. In refer to Beta-1 subunit it is quite interesting that some varieties with lack of Beta-1 band were present. In case of Beta-2 and Beta-3, only varieties with Beta-2 and /or Beta-3 lower intensity were observed. These results indicate that Myanmar local rice cultivars belonged to at least 7 variations for glutelin basic subunit, suggesting that Myanmar local rice cultivars possess a wide range of genetic diversity for glutelin basic subunit by SDS-PAGE.

To investigate more variations for glutelin basic subunit, 367 Myanmar local rice cultivars were analyzed by IEF and significant difference was observed in IEF profile of glutelin basic subunit. The 10 IEF bands of glutelin basic subunit polypeptides were observed in Kinmaze and IR36. pI8.13, pI8.24 bands are Kinmaze specific bands, as compared to IR36, while pI8.37, pI8.45, are IR36 specific bands, compared to Kinmaze. All of the IEF bands for glutelin basic subunit observed in Kinmaze and IR36 were also found in Myanmar local rice cultivars. In comparison to Kinmaze and IR36, new 3 IEF bands with pI8.35, pI8.40, and pI8.47, were detected in Myanmar local rice cultivars examined (Table 1). Based on the IEF profiles, Myanmar local rice cultivars were divided into 16 different types for glutelin basic subunit (Fig. 2). The variations were observed in 9 bands among 13 pI bands for glutelin basic subunit in Myanmar local rice cultivars (Table 1). These results indicate that glutelin basic subunits in

Myanmar local rice cultivars possess a wide variation in pIs as well as molecular mass, which points to the richness of Myanmar rice genetic resources for glutelin basic subunits. This variation in glutelin basic subunit will provide the available information to the breeding for rice grain quality.

This study was partly supported by Bio-oriented Technology Research Advancement Institution (BRAIN), Japan.

References

Kagawa, H., H. Hirano and F. Kikuchi, 1988. Variation of glutelin seed storage protein in rice (Oryza sativa L). Jpn. J. Breed. 38: 327-332.

Jahan, M.S., T. Kumamaru, H. Satoh and A. Hamid, 2003. Diversity of glutelin seed storage protein in Bangladesh rice germplasm. Genetic resources and crop evolution (in press).

Satoh, H., X. R. Rakotonjanahary and T.C. Katayama., 1990. SDS-PAGE analysis of storage proteins of cultivated rice collected in Madagascar, 1988. Kagoshima Univ. Res. Center S. Pac., Occ. Papers, 18: 101- 113.

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

Uemura, Y.J., H. Satoh, M. Ogawa, H. Suehisa, T. C. Katayama and A. Yoshimura, 1996. Chromosomal location of genes encoding glutelin polypeptides in rice. In Rice Genetics III, International Rice Research Institute, Manila, Philippines, pp 471-476.