Our research focuses on how plants can withstand stresses caused by climate change, in particular drought, heat and the continuing increase in the greenhouse gas CO2.

Research projects have profound implications for developing more drought and climate change resistant crops.

Stress-Induced Signal Transduction in Plant Guard Cells

Our research is elucidating the molecular and cell biological stress-induced signal transduction cascades in higher plant cells, examining the chain of events by which plants respond to elevated CO₂, the drought stress hormone abscisic acid, heat and salinity stress to mount specific resistance and adaptation responses. We have developed and adapted interdisciplinary and systems biological approaches to guard cells, which control water loss and CO₂ intake in plants and which have become a key model system for understanding dynamic cellular signal transduction and ion channel functions in plants.

Stomatal pores in the epidermis of leaves allow CO₂ influx into leaves from the atmosphere and also mediate transpirational water loss of plants (see figure). Two guard cells surround each pore and control the opening and closing of stomata. In guard cells, cell biological, molecular, patch clamp and time-resolved calcium imaging studies on genetic signaling mutants in Arabidopsis and in cereal grasses are allowing us to identify and characterize stress-induced signal transduction mechanisms and cascades. We are combining these analyses with new genomic, systems, bioinformatic and proteomic approaches towards discovering new signaling mechanisms and principles. We have identified CO₂ binding proteins, CO₂ sensors and early signal transduction mechanisms, including ion channels in guard cells through which elevated CO₂ closes stomatal pores. We have identified new early signal transduction mechanisms and contributed to the characterization and co-identified receptors for the plant stress hormone abscisic acid and have obtained molecular genetic, cell biological, genomic, biophysical whole plant physiological evidence for new genes and mechanisms in guard cells that reduce water loss of Arabidopsis during drought.

Plant Adaptation to Salinity and Heavy Metal Stress

A second effort in the lab focuses on identifying genes that mediate salt (sodium/salinity) stress resistance and heavy metal uptake and detoxification in plants. In this research we identified the plant HKT transporter family and showed its central role in mediating salinity resistance in the reference plant, Arabidopsis thaliana. Research on the staple crops rice and wheat is showing that this same HKT transporter mechanism plays a major role in determining salinity resistance. HKT gene-focused marker-accelerated molecular breeding efforts are indicating major improvements in yield, illustrating how basic discovery research is leading to innovation in agriculture.

Our research into heavy metal stress led to the parallel discovery of the genes encoding the central heavy metal detoxification enzymes in plants, phytochelatin synthases. Furthermore collaborative research identified the long sought family of transporters that mediate heavy metal and arsenic accumulation in plant vacuoles. These basic research advances can provide key tools for avoiding toxic heavy metal and arsenic accumulation in edible plant tissues, a problem facing millions of people today leading to cancer and other diseases. Furthermore, these basic research advances can contribute key tools for cost-efficient engineering plants for environmental remediation (bioremediation) by removal of heavy metals from soils.

Diagram: the role of stomata in how plants manage gas exchange and water balance.