Thylakoid membrane dynamics and state transitions in Chlamydomonas reinhardtii under elevated temperature

Abstract

Moderately elevated temperatures can induce state transitions in higher plants by phosphorylation of light-harvesting complex II (LHCII). In this study, we exposed unicellular algae Chlamydomonas reinhardtii to moderately elevated temperatures (38 °C) for short period of time in the dark to understand the thylakoid membrane dynamics and state transition mechanism. Here we report that under elevated temperatures (1) LHCII gets phosphorylated similar to higher plants and (2) there is decreased absorption cross section of photosystem II (PSII), whereas (3) there is no change in absorption cross section of photosystem I (PSI) indicating that LHCII trimers are largely disconnected with both photosystems under moderately elevated temperatures and (4) on return to room temperature after elevated temperature treatment there is a formation of state transition complex comprising of PSII-LHCII-PSI. The temperature-induced state transition mechanism also depends on stt7 kinase-like in light-induced state transition. The protein content was stable at the moderately elevated temperature treatment of 40 °C; however, at 45 °C severe downregulation in photosynthetic performance and protein content was observed. In addition to the known changes to photosynthetic apparatus, elevated temperatures can destabilize the PSII-LHCII complex that can result in decreased photosynthetic efficiency in C. reinhardtii. We concluded that the membrane dynamics of light-induced state transitions differs considerably from temperature-induced state transition mechanisms in C. reinhardtii.

Long- and short-term acclimation of the photosynthetic apparatus to salinity in Chlamydomonas reinhardtii. The role of Stt7 protein kinase

“…Similar temperature-induced-state transitions have been reported in A. thaliana ( Nellaepalli et al., 2011 ; Nellaepalli et al., 2015 ) and C . reinhardtii ( Madireddi et al., 2019 ). Surprisingly, LHCII phosphorylation was also observed in long-term salt treatments (cells grown in 100 mM and 150 mM salt concentrations).…”

“…The absorption cross-section of the PSI and PSII can be modulated by anaerobiosis ( Nellaepalli et al., 2012 ) and elevated temperature ( Nellaepalli et al., 2011 ; Nellaepalli et al., 2015 ; Madireddi et al., 2019 ). Anaerobiosis-induced state transition was observed in Arabidopsis thaliana , which also mimics the light-induced state transitions.…”

“…The impact of moderately elevated temperature on state transitions is well documented ( Nellaepalli et al., 2011 ; Nellaepalli et al., 2015 ; Madireddi et al., 2019 ). Dark, elevated temperatures up to 40°C can induce LHCII phosphorylation; thus, state transitions occur in these conditions.…”

“…In Chlamydomonas (C.) reinhardtii , thylakoid membrane dynamics could have altered under elevated temperature due to a change in membrane fluidity. The state transition complexes separated using sucrose density centrifugation from C. reinhardtii under elevated temperature have shown the presence of a PSII–LHCII–PSI complex that can redistribute energy between two photosystems within the same complex ( Madireddi et al., 2019 ). In all these reports, the dark-induced state transition may be involved in photoprotection and balance of the excitation pressure on both photosystems.…”

Bridging Carotenoid-to-Bacteriochlorophyll Energy Transfer of Purple Bacteria LH2 With Temperature Variations: Insights From Conformational Changes

“…The light-harvesting apparatus in photosynthetic organisms are diverse in order to adapt to different living environments, including temperature variations ( Cogdell et al, 2006 ; Solov’ev and Erokhin, 2008 ; Ivanov et al, 2017 ; Madireddi et al, 2019 ; Croce, 2020 ). Exploring the mechanisms of temperature adaptation has a profound impact on understanding the energy transfer process of photosynthesis.…”