Submitted to: Biomed Central (BMC) Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2018
Publication Date: 1/10/2018
Citation: Chen, J., Burke, J.J., Xin, Z. 2018. Chlorophyll fluorescence analysis revealed essential roles of FtsH 11 protease in regulation of the adaptive responses of photosynthetic systems to high temperature. Biomed Central (BMC) Plant Biology. doi:10.1186/s12870-018-1228-2. Interpretive Summary: High temperature is a major environmental stress negatively impact crop yield. However, the mechanism how plants tolerate high temperature is not clear. Using Arabidopsis high temperature sensitive mutant, ftsh11, ARS scientists at Lubbock demonstrated that the efficiency for photosynthetic systems in utilizing the absorbed light energy for photosynthesis were affected by the FtsH mutation in multitude of aspects when the environmental temperature raised to moderately high (30°C). The results help to understand the role of this chloroplast-targeted FtsH protease in regulating stability of photosystems under high temperature stress and may lead to improved high temperature tolerance in crops.
Technical Abstract: Background: Photosynthetic systems are known to be sensitive to high temperature stress. To maintain a relatively “normal” level of photosynthetic activities, plants employ a variety of adaptive mechanisms in response to environmental temperature fluctuations. Previously, we reported that the chloroplast-targeted AtFtsH11 protease played an essential role for Arabidopsis plants to survive at high temperatures and to maintain normal photosynthetic efficiency at moderately elevated temperature. To investigate the factors contributing to the photosynthetic changes in ftsh11 mutant, we performed detailed chlorophyll fluorescence analyses of dark-adapted mutant plants and compared them to Col-0 WT plants under normal, two moderate high temperatures, and a high light conditions. Results: We found that mutation of FtsH11 gene caused significant decreases in photosynthetic efficiency of photosystems when environmental temperature raised above optimal. At moderate high temperatures, the ftsh11 mutant showed significant 1) decreases in electron transfer rates of photosystem II (PSII) and photosystem I (PSI), 2) decreases in photosynthetic capabilities of PSII and PSI, 3) increases in non-photochemical quenching, and a host of other chlorophyll fluorescence parameter changes. We also found that the degrees of these negative changes for utilizing the absorbed light energy for photosynthesis in ftsh11 plants were correlated with the level and the duration of the heat treatments. For plant grown under normal temperature and subjected to the high light treatment, we found no significant differences in all chlorophyll fluorescence parameters measured between the FtsH11 mutant and Col-0 WT plants Conclusions: The results of this study show that AtFtsH11 is essential for normal photosynthetic function under moderately elevated temperatures. The results also suggest that the AtFtsH11 protease mediated network plays critical roles for maintaining the thermostability and possibly structural integrity both photosystems under elevated temperatures. Elucidating the underlying mechanisms of FtsH11 protease in photosystems may lead to improvement of photosynthetic efficiency under heat stress conditions, hence, plant productivity.