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Biosynthesis of Storage Protiens in Developing Endosperm of Rice (oryza Sativa L. Tribe Indica Cv. Nazirshail).

SUBOOH C. SARKER
Department of crop Botany, BAU, Mymensingh

Abstract/ Executive Summary:

An indegenous variety of rice, Nazirshail was grown hydroponically during the transplant aman season of 1989. Single stem (uniculm) was maintained. Total protein contents of the endosperms were analysed from 2 days after flowering (DAF) upto maturity of the grain. Synthesis of storage protein was found to be started from 4 DAF in the developing endosperms. Sodium-dody- cil-sulfate-polyacrylamide-gel-electrophoresis (SDS-PAGE) revealed that glutalin and prolamin started to be synthesized at around 4 DAF and 9 DAF, respectively. Glutelin was initially synthesized as a large molecular weight precursor polypetide which subsequently cleaved into two subunit structures of mature glutelin. Maximum content of this precursor protein was found to be at around 10 DAF. Cleavage into glutelin subunits continued, maintaining the steady state concentration of the precursor upto maturity of the grain. The molecular weights of the precursor and the two subunits of glutelin ware determined to be 57 kDa, 37-39 kDa and 21-22 kDa, respectively. Molecular weight of rice prolamin was 13 kDa. The mature endosperm of rice contained 11% of total protein of which about 60% was glutelin, 30% prolamin and the rest was albumin and globulin.

Keywords: Glutelin, Prolamin, Protein body, Storage protein, Rice.

Location: Department of Crop Botany, Bangladesh Agricultural University

Start Date:

End Date:

Program Area: Quality and Nutrition

Commodity: Rice

Objectives:

To characterize the stage specificity of glutelin and prolamin biosynthesis by analyzing the proteins of developing endosperms, electrophoretically.

Methodology:

Rice plants (Oryza sativa L. cv. Nazlrshail) were grown hydroponicallv in the plastic shed of the department of Crop Botany, Bangladesh Agricultural University according to Yoshida et al. (1976). About 100gm healthy seeds were surface sterilized with 0.1 % HgCl₂. for one minute. The seeds were then thoroughly washed with tap water and kept over night under running tapwater. After 24 hours of soaking, the seeds were set for germination. Two weeks after germination, seedlings were transplanted into 4 L plastic pots containing nutrient solutions. pH of the nutrient solution was maintained around 5.0 using mixed indicator and 1 N NaOH The culture solution was renewed once a week during early growth stages and twice a week during peak vegetative growth stage upto flowering. pH of the culture solution was maintained every day. At various stages of developing grains and at maturity. spikelets were collected. dehusked and the embryo were removed. Albumin. glubulin, prolamin and glutelins were extracted of the endosperm (10g) sequentially with 100 ml buffer each of 50mM Tris HCI, pH 7.5, containing 0.1 mM EDTA (buffer A); buffer A containing 1.0 M NaCI; 55% n propanol and 1% (v/v) lactic acid, respectively. Albumin and globulins were precipitated with same volume of acetone. prolamin with 0.5% NaCI and glutelin was precipitated with (NH₄)₂SO₄. After centrifugation pillets were dissolved in respective extraction buffer (1ml) for protein quantificantion. For SDS-PAGE 0.5 ml of each concentrated protein solution was added to 0.5 ml of 8M urea, containing 50 mM 2-mercaptoethanol, 4% SDS and 125 mM Tris-HCI, pH 6.8.

Source of Information: Proc. BAU Res. Prog. 5: 156-162, 1991

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The mature endosperm of rice contained 11% of total protein of which about 60% was glutelin, 30% prolamin and the rest was albumin and globulin.

Knowledge Management: Report/Proceedings