Maarten Chrispeels
Distinguished Professor Emeritus of Biology, UCSD
e-mail: mchrispeels@ucsd.edu
Lab Homepage: Chrispeels Lab
Plants have unique adaptations and responses to cope with their physical and biological environment. In our laboratory we study both basic cellular processes and unique plant-specific problems. A major research focus is on the study of aquaporins (water channel proteins). In plants, these integral membrane proteins are found in the plasma membranes and vacuolar membranes. In Arabidopsiswe found at least 23 different expressed aquaporin genes. Why is it necessary to facilitate the flow of water through membranes? Isn't water movement by diffusion through the bilayer sufficient? (In humans, aquaporins are found in the kidney and that organ's role in water filtration is legendary!) In plants, aquaporins come into play when water moves through the plant as part of the transpiration stream. This flow will be facilitated by the presence of membrane proteins that enhance water permeability by 10 to 20 fold. Secondly, water needs to enter rapidly into cells when they are expanding. Unlike animal cells, plant cells grow enormously in size after they divide and a huge vacuole is created. Thirdly, the vacuole and the cytoplasm must be in constant osmotic equilibrium, requiring rapid water flux through the vacuolar membrane. How is the activity of aquaporins regulated and in response to which signals? Does drought or salt stress affect the expression of some of these genes?
The second area of research is completely different from the first one. We study a family of a-amylase inhibitors found in seeds of the common bean and some of its close relatives. This "defense" protein inhibits the a-amylase in the guts of bruchid larvae and prevents the larvae of certain bruchid species from burrowing into the seeds. However, other species of bruchids seem to have evolved that thrive on beans and their ability to digest starch is impaired by this inhibitor. Why not? Can they digest the inhibitor? Have their amylases evolved so that they are not inhibited? To try to understand this we are cloning the cDNAs of amylases of bruchid larvae, and studying the interaction between insect amylases and bean amylase inhibitors. In addition, we are engineering the inhibitor genes into other legumes to make them resistant to bruchids, a biotechnological approach with great potential to improve crop yields in developing countries.
Pathways of water flow in plant tissues
Martinez, I.M., M.J. Chrispeels, (2003). Genomic analysis of the unfolded protein response in Arabidopsis shows its connection to important cellular processes. Plant Cell, Vol. 15, 1-16.
Apone, F., N. Alyeshmerni, K. Wiens, D. Chalmers, M.J. Chrispeels and G. Colucci. (2003). The G-protein coupled receptor GCR1 and the +/- -subunit of the heterotrimeric G-protein GPA1 regulate cell division through activation of phosphatidylinositol-specific phospholipase C (PI-PLC). Plant Physiol. 133: 571-579.
Bibyut, K., S.A. Moore, W. Tate, L. Molvig, R.L. Morton, D. P. Rees, P. Chialese, M. J. Chrispeels, L. M. Tabe and T.J.V. Higgins (2004). Transgenic chickpea seeds expressing high levels of a bean alpha-amylase inhibitor. Molecular Breeding 14: 73-82.
Aroca, R., G. Amodeo, S. Fernandez-Illescas, E.M. Herman, F. Chaumont and M. J. Chrispeels (2005). The roles of aquaporins and membrane damage in chilling and hydrogen peroxide induced changes in the hydraulic conductance of maize roots. Plant Physiology 137: 341-353.
Chrispeels, M.J. (2005). L'agricoltura del nuovo millenio mette radici nella genomica. Darwin March/April pp. 64-73.
Maarten Chrispeels received his Ph.D. from the University of Illinois and was a postdoctoral fellow at the DOE Plant Research Laboratory at Michigan State University. Professor Chrispeels was awarded a Guggenheim Fellowship and is a member of the National Academy of Sciences. He is the editor in chief of Plant Physiology.