Poster: Seed Biology

Abs # 542: Expression patterns and activation of rice glutamate decarboxylases

Presenter:	Oh, Suk-Heung , shoh@core.woosuk.ac.kr
Authors	Oh, Suk-Heung  (A)   Lee, In-Tae  (A)   Choi, Won-Gyu  (A)   Yun, Song Joong  (B)
Affiliations:	(A): Dept. of Biotechnology, Woosuk University (B): Faculty of Biol. Resources Sci., Chonbuk Nat'l University

We have isolated an Oryza sativa GAD (OsGAD) clone from rice root cDNA libraries and the OsGAD1 and OsGAD2 clones from dehulled rice seeds' RNA. The OsGAD genes were cloned into a high copy number plasmid pVUCH. The expression of 56~58 kDa OsGAD proteins were identified by Western-blot analysis using an anti-GAD monoclonal antibody. To help elucidate the specific function of OsGADs in Oryza sativa their expression patterns were evaluated. Dehulled seeds of rice were sterilized and germinated for 3 days. The results of RT-PCR analysis show that OsGAD and OsGAD1 are specifically expressed in ungerminated rice seeds. In contrast, OsGAD2 was found to be specifically expressed in germinated rice seeds. OsGAD has a highly conserved tryptophan residue but lacks the lysine cluster at the C-proximal position and other stretches of positively charged residues. OsGAD1 has the highly conserved tryptophan residue and C-proximal lysine cluster but OsGAD2 has not (Akama et al., 2001. Biochimica et Biophysica Acta 1522, 143-150). The differences between the C-terminal regions of OsGAD, OsGAD1 and OsGAD2 suggest the possibility of the difference in calmodulin-binding ability. We are currently examining the OsGAD enzymes to determine whether they are activated by calmodulin and whether they are Ca²⁺-dependent. (This work was supported by Korea Research Foundation Grant, KRF-2002-042-F00005).