Minisymposium 1: Nutrient Biology

Abs # 11004: Genetic manipulation of a pyrophosphate-driven vacuolar H+-pump (AVP1): Impact on nutrition, growth and development, and plant response to abiotic stress

Presenter:	Gaxiola, Roberto A, roberto.gaxiola@uconn.edu
Authors	Gaxiola, Roberto A (A)   Li, Jisheng  (A)   Undurraga, Soledad F (A)   Yang, Haibing  (A)
Affiliations:	(A): University of Connecticut

Arabidopsis plants engineered to overexpress the vacuolar H+-pyrophosphatase AVP1(AVP1-OX) have enhanced tolerance to salinity and drought stress. The enhanced tolerance is most easily explained by an enhanced uptake of ions into vacuoles. Presumably, greater AVP1 activity in vacuolar membranes provides increased H+ to drive the secondary active uptake of cations into the vacuole. A compensatory transport of anions is expected in order to maintain electroneutrality. The resulting elevated vacuolar solute content would allow for greater osmotic adjustment capacity, permitting plants to survive under conditions of low soil water potential. Transport studies consistent with the above hypothesis show that tonoplast vesicles from roots of AVP1-OX Arabidopsis and tomato plants have higher PPi-dependent Ca2+ uptake than controls. Further more ,these AVP1-OX tomato plants are also drought tolerant (Abs. Gaxiola et al). Arabidopsis AVP1-OX plants are capable of growing in the presence of toxic levels of Mn2+ and Cd2+ (Abs. Undurraga et al). Interestingly, the ectopic overexpression of AVP1 in Arabidopsis also improves growth in limiting K+ and PO43- media. Preliminary data show that roots of AVP1-OX plants acidify the medium more than controls when grown on limiting K+. This enhanced capability to acidify the medium could be the result of an extended root hair area present in the AVP1-OX roots (Abs. Yang et al). Turgor-dependent cell expansion relies on water uptake that follows solute accumulation in the vacuole. Interestingly the ectopic over-expression of AVP1 results in enlarged shoot organ size due to enhanced cell proliferation. Furthermore, incubation in shoot induction medium of cotyledons, true leaves, inflorescence stems, hypocotyls and root explants from the AVP1-OX lines results in a dramatic enhancement of their de novo organogenesis capacity. The differential expression patterns of key molecular marker genes in control and transgenic explants are consistent with a central role of AVP1 in the early events leading to de novo organogenesis (Abs. Li et al ). The pleiotropic effects that the overexpression of this vacuolar H+-pump triggers are consistent with the key role that H+-gradients play as the driving force for a plethora of physiological and developmental processes in plants.