Poster: Protein Targeting & Vesicular Trafficking

Abs # 1188: Expression of ARF1 and SAR1 GTP-binding proteins at different developmental stages in Pisum sativum

Presenter:	Memon, Abdul R, armemon@rigeb.gov.tr
Authors	Memon, Abdul R (A) (B)  Keskin, Birsen C (A)   Yuca, Esra  (A) (B)
Affiliations:	(A): TUBITAK, Inst Genetic Engineering & Biotech (B): Yildiz Technical University, Dept. of Biology

Small membrane vesicles mediate a large part of protein transport between various organelles. This vectorial transport involves two distinct small GTPases (Sar1/Arf1), coatomers (COPI/COPII) and various other membrane components including cargo receptors and SNAREs. COPI and COPII coated vesicles have been demonstrated in plant cells, and various Arf1 and Sar1 homologous have been identified at both gene and protein levels. However, little is known about the mechanism(s) of COP-coat formation or the nature and recruitment of COP-vesicles cargoes in plants. We have selected pea as a model leguminous plant (Memon et.al. Biochem Biophy Res Com., 193: 809-813, 1993) to elucidate the protein transport mechanisms. We followed the expression pattern of Arf1 and Sar1 proteins at various developmental stages in roots and shoots. Our immunoblot results showed that Arf1 and Sar1 were expressed several times more in shoots compared to roots. Light grown shoots showed around ten times more Sar1 expression than dark grown shoots. The increase in Arf1 expression in light grown shoots was also observed compare to dark grown one but the differences were less dramatic. ARF1 was mostly concentrated in crude Golgi fractions and SAR1 was highly concentrated in crude ER fractions of pea shoots. Both proteins were also detected in supernatant fractions (around 40,000 g). Plants were grown in dark and samples were taken at different developmental stages (Embryo, 6th,12th,and 18th day). ARF1 expression level in the microsomal fractions of embryo was around 5 times more than the endosperm and plumules expressed around two times more Arf1 than radicles. Expression of Sar1 at these developmental stages is in progress.