Our research topics:
The adaptation of crop plants to environmental stress conditions:
Environmental stress due to drought and salinity are the most serious factors limiting the productivity of agricultural crops, which are predominantly sensitive to low soil moisture and the presence of high concentrations of salts in the soil. The relevance of solutions to these problems is of obvious importance for world’s agriculture in general and the State of California in particular. Crop production in both the Imperial Valley and the San Joaquin Valley is severely affected by limiting water resources and the progressive salinization of the soil. In addition, water resources are becoming increasingly scarce and water quality is decreasing, thus increasing the severity of the problem. Our work demonstrated that transgenic plants expressing IPT (isopentenyltransferase), a gene encoding an enzyme mediating cytokinin (CK) synthesis, under the control of the senescence- and stress-induced SARK promoter were able to survive drought stress with a significant yield advantage over wild-type plants. Moreover, the PSARK::IPT transgenic plants displayed reduced yield penalty and improved grain quality. Our working hypothesis, based on recent findings in our laboratory, is that in addition to the induction of protective mechanisms against the deleterious effects of stress, the partitioning of assimilates and nutrients between source and sink tissues is a key factor in the adaptation of crop plants to adverse environmental conditions in general and water deficit in particular. We have identified a number of genes that regulate hormone homeostasis, alter starch metabolism, and modify the plant source/sink balance during stress. We are characterizing the effect of these genes in ameliorating the effects of stress in the plants and pyramiding genes with complementary function. We use a System Biology approach combining molecular biology, plant transformation, genomics, proteomics and metabolomics to assess phenotype and gene function. We focus our work on cereals, using rice. Millet, wheat and the cereal model plant Brachypodium. Our work has generated a number of patents that have been licensed by the California biotechnology industry to develop salt tolerant and water use efficient cultivars.
The biochemical and molecular basis of fruit ripening:
We are applying a systems biology approach (that combines genomics, metabolomics, proteomics, biochemistry, pre- and post-harvest physiology) to identify ethylene-mediated changes during fruit maturation, ripening and senescence aiming at the identification of key molecular and biochemical determinants that could be manipulated for the development of cultivars with enhanced quality traits. In particular, we are characterizing the metabolite profiles of climacteric and non-climacteric plum fruits and the protein/enzymes associated with ripening processes in climacteric and non-climateric plum fruits. We are analyzing the expression of genes associated with the development of quality traits in climacteric (and non-climacteric fruits) and identifying metabolic/enzymatic pathways associated with pre- and post-harvest quality traits.
Role of ion and pH homeostasis in plant growth and stress responses:
Our general is the characterization and identification of the biochemical and biophysical processes that regulate cell growth and cell expansion. We focus on the regulation of the transport of solutes (K+ and Na+ in particular), the establishment of ion and pH homeostasis in the plant cell and their impact on the regulation of cell volume and the traffic of membrane and their protein cargo between the different cell compartments, and the cell response to environmental changes. Our research builds on the work done by our group towards the characterization of the roles of the intracellular NHX-type of transporters. We have shown the paramount roles of the endosomal NHX5 and NHX6 in plant growth and development, and the vacuolar NHX1-NHX4 in floral development, cell expansion and ionic regulation. We apply a multidisciplinary approach to establish the functional role(s) of each intracellular NHX, combining physiology, biochemistry, genetics, genomics, vesicular membrane transport, the heterologous gene expression in plants, and use of multiple NHX-knockout lines developed in our laboratory.