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ARS Home » Research » Publications at this Location » Publication #103522
Title: ROLE OF RUBISCO ACTIVASE IN HEAT STRESS EFFECTS ON PHOTOSYNTHESIS

Author
item KELLY, WALTER - PLANT BIOLOGY UOFI URBANA
item WHITMARSH, CLIFFORD
item PORTIS JR, ARCHIE

Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 8/6/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The reversible inhibition of photosynthesis at moderately elevated temperatures correlates with a decrease in the activation state of rubisco. In previously reported in vitro assays, activase was found to loose activity following incubation at temperatures in the range of 30-40degC. This lead to the hypothesis that temperature induced alteration of activase is primarily responsible for the inhibition of photosynthesis in this range. However, when the in vitro assay of activase ATPase activity was carried out at the incubation temperature, the optimum temperature was higher, such that active activity was about the same at 40 deg C as at 25 deg C. This latter finding appears to challenge the hypothesis, but the interaction between activase and rubisco may be more temperature sensitive than the intrinsic ATPase activity of activase. We tested this idea using in vitro experiments to assay the rubisco activation activity of activase (as opposed to just the ATPase activity) at varying temperatures. In assays using wild type rubisco and activase extracted from spinach, the activation activity of activase was the same at 37 deg C as at 31 deg C, although the spontaneous activation of rubisco was greater at the higher temperature. This does not support the hypothesis that activase is the primary target for heat inactivation, and suggests either that the reversible heat-induced inhibition of photosynthesis is due to a mechanism which is independent of activase, or that heat primarily affects another component and this single is then transduced by activase, resulting in a decrease in rubisco activation state. Work supported by NSF/DBI Grant 96-02240.