Xanthophyll cycle induction by anaerobic conditions under low light in Chlamydomonas reinhardtii
- PDF / 429,631 Bytes
- 15 Pages / 595.276 x 790.866 pts Page_size
- 40 Downloads / 161 Views
Xanthophyll cycle induction by anaerobic conditions under low light in Chlamydomonas reinhardtii Cecilia Faraloni & Giuseppe Torzillo
Received: 23 October 2012 / Revised and accepted: 9 January 2013 # Springer Science+Business Media Dordrecht 2013
Abstract The effect of anaerobiosis on the induction of the xanthophyll cycle was investigated in Chlamydomonas reinhardtii. The results showed that, anaerobiosis obtained by either sulfur starvation or by bubbling nitrogen in the culture grown in complete medium induced the xanthophyll cycle even when cultures were exposed to low light conditions. The zeaxanthin content reached 35 mmol mol−1 Chl a, after 110 h in anaerobic sulfur-starved cultures, and 30 mmol mol−1 Chl a within 24 h in sulfur replete cultures bubbled with nitrogen. Both starved and nonstarved cultures grown under aerobic conditions, did not exhibit any sizeable increase in the zeaxanthin content. Chlorophyll fluorescence measurements revealed a decrease in the maximum photochemical quantum yield of PSII (F v /F m ) by more than 50 %. The chlorophyll fluorescence kinetics (OJIP) analysis showed a strong rise at the J-step indicating a strong reduction of QA. Our findings demonstrated that anaerobiosis in low light exposed cultures induced the xanthophyll cycle through a strong increase of the level of plastoquinone pool reduction, which was associated to the formation of a transthylakoid membranes proton gradient, while in dark anaerobic cultures, no appreciable induction of xanthophyll cycle could be observed, despite the sizeable increase in non–photochemical quenching. Keywords Chlamydomonas reinhardtii . Xanthophyll cycle . Anaerobiosis . Chlorophyll fluorescence . Plastoquinone pool . Non-photochemical quenching C. Faraloni (*) : G. Torzillo Istituto per lo Studio degli Ecosistemi (ISE), CNR, Via Madonna del Piano, 10-50019 Sesto Fiorentino Florence, Italy e-mail: [email protected]
Introduction Photosynthetic microorganisms have evolved inducible system to acclimate their metabolism to survive under environmental stress conditions, such as high light exposure and limiting nutrient conditions (Grossman 2000; Takahashi et al. 2001). Under these conditions, photosynthetic organisms may be subjected to an excessive degree of reduction of the photosynthetic electron transport chain, which can generate oxidized intermediates promoting damage to surrounding biomolecules (Demmig-Adams 1990, 2003) and the decrease of photosynthetic activity. This process is related to the destruction of the photosystem II (PSII) reaction centers which results in the inhibition of electron transport (Melis 1999; Jin et al. 2003). The dissipation of the excess absorbed light energy occurs via the non-photochemical quenching (NPQ) of chlorophyll fluorescence, a harmless non-radiative pathway dissipation of energy. This defensive strategy involves the synthesis of photoprotective carotenoid pigments, such as lutein and the xanthophyll cycle pigments (Björkman 1987; Demmig-Adams et al. 1989; Gilmore and Yamamoto 1993, 2001; G
Data Loading...
