Title: Role of FtsH11 protease in thermoprotection of photosynthetic systems Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: July 18, 2007
Publication Date: July 21, 2007
Citation: Chen, J., Xin, Z., Burke, J.J. 2007. Role of FtsH11 protease in thermoprotection of photosynthetic systems[abstract]. Drymen Photosynthesis Satellite Workshop. Drymen, Scotland. July 18-21, 2007. Technical Abstract: As sessile organisms, plants employ multiple mechanisms to cope with seasonal and daily temperature fluctuations associated with their habitats. AtFtsH11 protease gene was identified via map-based cloning as essential for Arabidopsis plant to survive at moderate high temperatures. Arabidopsis genome contains 12 predicted FtsH genes, with all previously characterized FtsH proteases playing roles in alleviation of light stress through degradation of unassembled thylakoid membrane proteins and photodamaged D1 protein. Under high and normal light conditions at 21ºC, ftsh11 mutants were indistinguishable from wild type plants in photosynthesis capability and in growth and development. However, under temperatures at 30ºC or above, mutant plants display a host of dramatic changes in photosynthetic parameters, cessation of growth and development, and eventual death. Thermosensitive phenotypes were observed at all developmental stages and in all green tissue types. Cotyledons of 21ºC-dark germinated mutant seedlings failed to turn green after being transferred to light at 30ºC. When mutant seedlings were exposed to 30°C, photosynthetic capabilities, measured as chlorophyll content, chl a/b ratios, PSII quantum yield, ETR, NPQ, qN and some other parameters changed significantly. During the 30ºC treatment, the minimal fluorescence Fo continued to increase while T1/2 continued to decrease in mutant leaves. The results suggested that FtsH11 plays critical roles both in the early stages of chloroplast biogenesis and in maintaining thermostability of photosynthetic systems at high temperatures. Overexpression of FtsH11 genes from both Arabidopsis and pea were able to complement the thermosensitive phenotypes of ftsh11 mutants, suggesting a conserved role of FtsH11 protease in alleviation of high temperature stress in photosystems of higher plants.