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.
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.
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.