ASGSB 1998 Annual Meeting Abstracts

[61]
FUNCTION AND REGULATION OF TCH2 EXPRESSION IN ARABIDOPSIS.   K.A. Johnson and J. Braam, Biochemistry & Cell Biology, Rice Univ., Houston.

Plants are capable of adapting to diverse environments. What proteins function to alter morphogenesis in response to stimuli? An early response to a variety of environmental stimuli, like touch, darkness, and temperature shocks, is the induction of expression of TCH2 in Arabidopsis. TCH2 encodes a Ca2+-binding protein with 44% amino acid identity to calmodulin. Transgenic plants have been generated which express the uidA gene encodingЯ-glucuronidase (GUS) under control of ~1 kb TCH2 upstream sequences. This upstream sequence is sufficient for induction of TCH2-driven GUS expression following touch, darkness, and temperature shifts. Major sites of basal level TCH2-driven GUS activity are root tips and branch points. GUS activity is also observed within the floral tissues, with staining observed during stigmatic papillae and pollen maturation, and stigmatic staining disappearing after fertilization. TCH2-driven GUS activity is also observed in guard cells following stimuli known to result in stomatal closure. We are investigating the role of TCH2 in closure of the stomata. Another prominent site of TCH2-GUS expression is the hydathode. Hydathodes are passive pores on the leaf margin of many plants that are involved in guttation (water release in response to root pressure). TCH2 expression at this site may indicate a role in biogenesis and/or function of these complex structures in Arabidopsis. (Supported by NASA Specialized Center for Research and Training, grant no. NAGW 5007.)

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