Location: Children's Nutrition Research CenterTitle: Arabidopsis sodium dependent and independent phenotypes triggered by H+-PPase up-regulation are SOS1 dependent) Author
Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2011
Publication Date: 2/15/2012
Citation: Undurraga, S.F., Santos, M.P., Paez-Valencia, J., Yang, H., Hepler, P.K., Facanha, A.R., Hirschi, K.D., Gaxiola, R.A. 2012. Arabidopsis sodium dependent and independent phenotypes triggered by H+-PPase up-regulation are SOS1 dependent. Plant Science. 183:96-105. Interpretive Summary: Improved yield requires that crop plants grow in a variety of soil conditions and maintain robust growth. The movement of noxious metals and salts within plant cells are tightly regulated. Our findings here demonstrate that one particular transporter that was previously thought to only move sodium is also required for a large subset of growth and development events. These insights provide new elements to understanding the mechanisms that regulate salt tolerance, root growth, mineral nutrition and transport activities. Future work should broadly examine the substrate specificity and this transporter and also may lead to means of engineering plants that have both improved salt tolerance and more biomass.
Technical Abstract: The goal of the study and research was to coordinate regulation of transporters at both the plasma membrane and vacuole contribute to plant cell’s ability to adapt to a changing environment and play a key role in the maintenance of the chemiosmotic circuits required for cellular growth. In this study, the plasma membrane (PM) Na+/H+ antiporter (SOS1) is involved in salt tolerance, presumably in sodium extrusion; the vacuolar type I H+-PPase AVP1 is involved in vacuolar sodium sequestration, but its overexpression has also been shown to alter the abundance and activity of the PM H+-ATPase. We studied and investigated the relationship between these transporters utilizing loss-offunction mutants of SOS1 (sos1) and increased expression of AVP1 (AVP1OX). We observed that heightened expression of AVP1 enhances pyrophosphate-dependent proton pump activity, salt tolerance, ion vacuolar sequestration, K+ uptake capacity, root hair development, osmotic responses, and PM ATPase hydrolytic and proton pumping activities. The results showed that in sos1 lines overexpressing AVP1, these phenotypes are negatively affected demonstrating that sos1 is epistatic to AVP1. The conclusion is that enhanced AVP1 protein levels require SOS1 and this regulation appears to be post-translational.