Poster: Mineral nutrition

Abs # 203: Interaction between sos1 Mutation and AVP1 overexpression in Arabidopsis thaliana: Evidence for an Epistatic effect and a Role in Potassium Nutrition

Presenter:	Undurraga, Soledad F, soledad.f.undurraga@uconn.edu
Authors	Undurraga, Soledad F (A)   Gaxiola, Roberto A (A)
Affiliations:	(A): University of Connecticut

Transgenic plants overexpressing AVP1, a gene that encodes the vacuolar H+-pyrophosphatase, are more salt- and drought-tolerant than their control counterparts. They have a higher Na+ content in their leaves. Transport evidence with isolated tonoplast vescicles indicates that transgenic plants have higher PPi-dependent Ca2+ uptake than controls (Gaxiola et al, 2001, PNAS 98:11444-11449). Presumably, the greater PPi-dependent proton pumping activity in vacuolar membranes provides increased amount of H+ in the vacuolar lumen. This would increase the proton motive force to drive secondary transport of cations into the vacuole (Gaxiola et al, 2002, Plant Physiol 129:967-973). SOS1 is a plasma membrane Na+/H+ antiporter (Shi et al, 2000, PNAS 97:6896-6901). sos1 mutant plants are sensitive to low concentrations of Na+ and grow poorly under low potassium conditions (Wu et al, 1996, Plant Cell 8:617-627). SOS1 overexpression confers salt tolerance (Shi et al, 2003, Nature Biotech 21:81-85). In order to establish if there is an epistatic effect of AVP1 overexpression over the sos1 mutation, we crossed sos1-1 mutants with two AVP1 overexpressing lines. We selected plants that were homozygous for both traits. All the AVP1/AVP1-sos1-1/sos1-1 lines tested were sensitive to 50 mM NaCl under hydroponic conditions. These results are consistent with an epistatic effect of sos1 mutation over AVP1 overexpression in regard to salt-tolerance. Interestingly, all plants homozygous for the sos1-1 allele showed reduction in shoot biomass and inhibition of root hair growth when grown under low potassium concentrations.