Roberto Gaxiola
Finding ways to improve productivity in marginal agricultural lands has been the driving force of my research program. Enhanced root mass is expected to increase crop biomass and seed yields, making the root system an extremely attractive candidate for engineering crops to step up productivity.
Through the overexpression of a plant H+-PPase we have engineered plants (Arabidopsis, tomato, rice) that can grow in the presence of toxic levels of salts, develop very robust root systems and therefore resist extended drought and thrive in marginal soils. We have been able to demonstrate that the H+-PPase in not only involved in vacuolar pH homeostasis but that in addition controls auxin transport and consequently auxin-dependent development (i.e., root systems).
Our current work focuses on three research themes to further understand and capitalize upon the dramatic effects of H+-PPases on plant development and its utility in enhancing food and bio-fuel production:
First, we are characterizing the effects of type I H+-PPases on root system development and define their mode of action at the molecular and cellular level using Arabidopsis and rice as models.
- We are testing if the localization (i.e., tonoplast, endosomes, plasma membrane) of plant H+-PPases is tissue dependent and if it varies with developmental and/or environmental cues.
- We are looking for H+-PPases interacting proteins (i.e., kinases, phosphatases, 14-3-3) that would regulate their activity and/or intracellular localization.
Second, we are characterizing the effects of H+-PPase over-expression on candidate crops for enhanced food and fuel production, i.e., rice, corn, sweet sorghum, medicago, alfalfa, and cotton.
Third, we are using genetic engineering for gene pyramiding in order to introduce several quality characters that could result in a further improved genotype (i.e., co-expression of H+-PPases and vacuolar Cation/H+ exchangers, and/or H+-PPases and plasma membrane Cation/H+ exchangers).
Selected Publications
Yang, H., Knapp, J., Koirala, P., Rajagopal, D., Peer, W.A., Silbart, L., Murphy, A., and Gaxiola, R. (2007). Enhanced phosphorus nutrition in monocots and dicots over-expressing a phosphorus-responsive type I H+-pyrophosphatase. Plant Biotechnology Journal 5, 735-745.
Gaxiola RA, Palmgren MG, Schumacher K (2007). Plant proton pumps. FEBS Letters 581: 2204-2214
Park, S., Li, J., Pittman, J.K., Berkowitz, G.A., Yang, H., Undurraga, S., Morris, J., Hirschi, K.D., and Gaxiola, R.A. (2005). Up-regulation of a H+-pyrophosphatase (H+-PPase) as a strategy to engineer drought-resistant crop plants. Proc Natl Acad Sci USA 102, 18830-18835.
Li, J., Yang, H., Peer, W.A., Richter, G., Blakeslee, J.J., Bandyopadhyay, A., Titapiwantakun, B., Undurraga, S., Khodakovskaya, M., Richards, E.L., et al. (2005). Arabidopsis H+-PPase AVP1 Regulates Auxin Mediated Organ Development. Science 310, 121 - 125.
Gaxiola, R.A., Fink, G.R., and Hirschi, K.D. (2002). Genetic Manipulation of Vacuolar Proton Pumps and Transporters. Plant Physiology 129, 967-973.
Gaxiola, R.A., Li J., Undurraga S., Dang L.M., Allen G.J., Alper S.L., and Fink G.R. (2001). Drought- and salt-tolerant plants result from overexpression of the AVP1 H+-pump. Proc Natl Acad Sci USA 98, 11444 - 11449.
Gaxiola, R.A., Rao, R., Sherman, A., Grisafi, P., Alper, S.L., and Fink, G.R. (1999). The Arabidopsis thaliana proton tranporters, AtNhx1 and Avp1, can function in cation detoxification in yeast. Proc Natl Acad Sci USA 96, 1480-1485.
Gaxiola, R.A., Rao, R., Sherman, A., Grisafi, P., Alper, S.L., and Fink, G.R. (1999). The Arabidopsis thaliana proton tranporters, AtNhx1 and Avp1, can function in cation detoxification in yeast. Proc Natl Acad Sci USA 96, 1480-1485.
Gaxiola, R.A., Yuan, D.S., Klausner, R.D., and Fink, G.R. (1998). The yeast CLC chloride channel functions in cation homeostasis. Proc Natl Acad Sci U S A 95, 4046-4050.
Gaxiola, R.A., Yuan, D.S., Klausner, R.D., and Fink, G.R. (1998). The yeast CLC chloride channel functions in cation homeostasis. Proc Natl Acad Sci U S A 95, 4046-4050.