Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Proceedings
Publication Acceptance Date: 3/20/2002
Publication Date: 6/25/2002
Citation: Van, K.N., Ehler, L.L., Livingston, D.P., Herman, E.M. 2002. Identification of a protein that interacts with a freezing-induced aquaporin in wheat crowns.. American Society of Plant Biologists Annual Meeting.
Interpretive Summary: When plants freeze, ice forms in an intercellular space known as the apoplast. As long as ice remains in the apoplast, the plant will survive. However, ice will attract water from inside the cell and over time the plant may actually be killed by drought stress. Therefore, the mechanism of water movement into and out of plant cells is a critical consideration when looking at freezing tolerance. This research describes 2 plasma membrane intrinsic protein (PIP) molecules that are called aquaporins because they regulate water movement in plant tissue. The activity of one is regulated by cool temperatures which result in hardening of the plants. It is located only in crown tissue which is the only part of the plant to survive freezing temperatures under certain conditions. Crown tissues give rise to new roots and shoots in the spring. In addition to PIP another protein which interacts with PIP was discovered. Research is underway to determine the function of the new protein.
Technical Abstract: Various abiotic stresses reduce crop yields and about 80% of wheat was lost by these abiotic stresses such as temperature, drought, flooding and salinity. Wheat survives subfreezing temperatures after a period of cold acclimation by regulating gene expression, stabilization of membranes and accumulation of sugars, other solutes and antifreeze proteins. Ice formation in the intercellular spaces subfreezing temperatures results in a decrease of water potential outside the cell, indicating by movement of liquid water from intracellular to extracellular space. The active control of water flow may be critical for adaptation to subfreezing temperatures. but the details of the mechanisms are not known. Water movement across the plasma and tonoplast membranes is mediated by aquaporins with various members of this gene family specific for development, stress and cellular distribution. We have isolated two different wheat aquaporin PIP (plasma membrane intrinsic protein) cDNA clones from cold-acclimated and subzero temperature-treated wheat crown cDNA library. One PIP, a PIP1 is a widely expressed vegetative aquaporins while the other a PIP2 is up-regulated by cold acclimation and exposure to freezing temperatures in crowns but not leaves and roots. The expression of the PIP2 correlates with water efflux from the crown in response of subfreezing temperature. Using yeast two hybrid system, a protein interacting with PIP2 was identified from cold treated wheat crown library. The protein interacts with the PIP2 but not the PIP1. Functional analysis of the PIP2 interactive protein is in progress.