ASGSB 1999 Annual Meeting Abstracts

GRAVITY, STRESS, CALCIUM AND GENE EXPRESSION IN AEQUORIN-EXPRESSING PLANTS. B. Stankovi, E. Shimps, K. Brown, E. Davies. Botany Department, North Carolina State University, Raleigh, NC 27695.

Cytoplasmic calcium is a major regulator of plant metabolism and its levels are under strict control, but it increases rapidly and transiently after stress treatments such as cold and touch. Gravity is also thought to affect Ca²⁺ levels, although no direct evidence has been provided for its role. However, in previous fluorescence microscopy studies Ca²⁺ could not be visualized for at least 1 min after gravistimulation and thus changes could have occurred more rapidly. In order to circumvent problems associated with the delay in taking readings imposed by the fluorescence microscopy techniques, we chose a different method using plants transgenic for the Ca²⁺-binding, light-emitting jellyfish protein aequorin. We subjected Arabidopsis and tomato plants to heat-wounding, vibration and gravity stimulation and measured cytoplasmic Ca²⁺ levels. Gravistimulation, heat-wound, or vibration caused rapid, 10- to 20-fold increase in cytoplasmic Ca²⁺ levels within several seconds following treatment. We also measured the levels of several transcripts after gravistimulation and heat-wounding to determine whether both treatments evoked the same transcriptional changes. Preliminary experiments suggest that the response at the level of gene expression (transcript accumulation) is different after gravistimulation and wounding, even though the increases in Ca²⁺ are similar.

(Supported by NASA grant 5-47574, the NC Space Grant Consortium, and the NC Agricultural Research Service).

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