Poster: Nutrient Biology

Abs # 409: Up-regulation of the vacuolar H+-pyrophosphatase AVP1 improves grow in limiting K+ and PO43- media

Presenter:	Yang, Haibing , haibingyang@yahoo.com
Authors	Yang, Haibing  (A)   Gaxiola, Roberto A (A)
Affiliations:	(A): University of Connecticut

Arabidopsis plants engineered to express a 35S::AVP1 transgene that encodes the vacuolar H+-pump pyrophosphatase have been shown to exhibit salt- and drought-tolerant phenotypes and to accumulate more K+ in their leaf tissue than control plants (Gaxiola et al, 2001). Furthermore, transport studies with isolated tonoplast vescicles indicate that transgenic plants have higher PPi-dependent Ca2+ uptake than controls (Gaxiola et al, 2001). These studies suggest that a proton-dependent vacuolar ion accumulation through secondary transporters is enhanced by AVP1 overexpression. Rye plants grown under deficient mineral conditions up-regulate the activity of the root vacuolar H+-pyrophosphatase(Kasai et al, 1998). These results are consistent with a role of the vacuolar H+-pyrophosphatase in the uptake of ions into roots. This mechanism could be explained by two hypothesis. Root vacuolar H+-pyrophosphatase could be also expressed in the plasma membrane, increasing the proton-driven ion uptake. Alternatively, increased ion accumulation in the vacuole could indirectly influence ion uptake at the plasma membrane. Here we present data on the effect that the ectopic over-expression of AVP1 has on the uptake of macronutrients K+ and PO43-. We found that AVP1 transgenic plants grow better than controls in media supplemented with limiting levels of K+ and PO43-. These transgenic AVP1 plants acidified the medium stronger than controls when grown at low K+ medium.