Identifying the basic molecular mechanisms by which plants respond to and mount resistance to environmental stresses is fundamental to understanding stress resistance mechanisms to these “abiotic” in plants and is an important goal for developing future strategies for engineering stress resistance in plants. Several abiotic stress mechanisms that we are characterizing are directly linked to water, including drought stress-induced signal transduction mechanisms, salinity resistance mechanisms and how plants respond to the continuing rise in the atmospheric CO2 concentration.
Our laboratory’s research is directed at the signal transduction mechanisms and pathways that mediate resistance to environmental (“abiotic”) stresses in plants, in particular responses to elevated CO2, drought, salinity stress, and heavy metal stress. These abiotic stresses have substantial negative impacts and reduce global plant growth and biomass production. These environmental stresses are also relevant in reference to climate change and to expanding available arable land to meet the food and energy needs of the growing human population.
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 plant cells respond to elevated CO2, the drought stress hormone abscisic acid 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 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 and early CO2 signal transduction mechanisms, including ion channels in guard cells through which elevated CO2 closes stomatal pores. We have recently 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.
A second effort in the lab focuses on identifying genes that mediate salt (sodium) 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 molecular breeding efforts are indicating major improvements in yield, illustrating how basic Arabidopsis 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 recent research has identified the long sought family of transporters that mediate heavy metal 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 engineering plants for environmental remediation (bioremediation) by removal of heavy metals from soils.
Members in our lab are being trained in interdisciplinary and systems biological techniques while pursuing individual research projects.
Julian Schroeder is Novartis Chair and Distinguished Professor in the Division of Biological Sciences at the University of California San Diego and is Director of the Plant Systems Biology NSF UCSD-Salk IGERT Graduate Training Program. He received his PhD working with Erwin Neher at the Max Planck Institute for Biophysical Chemistry in Göttingen Germany. Julian pioneered characterizations of plant ion channels, which led to models of their unique functions in plant biology. He also pioneered functional characterizations of genes encoding plant ion transport proteins and their roles in stress tolerance. His present research has identified mechanisms and genes that allow plants to withstand drought and salinity stress. His laboratory has discovered CO2-binding proteins and mechanisms that mediate plant responses to the continuing atmospheric CO2 elevation and leaf CO2 concentration changes and has found that these CO2 binding proteins can be used to increase the instantaneous water use efficiency of plants. Julian Schroeder has received awards, including the Presidential Young Investigator Award from NSF, the Charles Albert Shull Award from the American Soc. of Plant Biologists, the DFG Heinz-Maier-Leibnitz Research Prize, the Blasker Award in Environmental Science and Engineering, was named Highly Cited Researcher by the Institute for Scientific Information, received a Feodor-Lynen Fellowship from the Alexander von Humboldt Foundation as a post doctoral scholar and with collaborators shared the Cozzarelli Prize from PNAS (2010) and in a top 10 breakthrough of the year selected by Science (2009). He was Alexander von Humboldt Fellow at the Max Planck Institute in Martinsried Munich, is an elected Fellow of the American Association for the Advancement of Sciences (2006) and is a Chinese Academy of Sciences International Professor (2009).