Publication Date:
2012-07-25
Description:
Background: Ecotypes of Colobanthus qutensis Kunt Bartl (Cariophyllaceae) from Andes Mountains andMaritime Antarctic grow under contrasting photoinhibitory conditions, reaching differentialcold tolerance upon cold acclimation. Photoinhibition depends on the extent of photodamageand recovery capability. We propose that cold acclimation increases resistance to lowtemperature-induced photoinhibition, limiting photodamage and promoting recovery undercold. Therefore, the Antarctic ecotype (cold hardiest) should be less photoinhibited and havebetter recovery from low-temperature-induced photoinhibition than the Andean ecotype. Bothecotypes were exposed to cold induced photoinhibitory treatment (PhT). Photoinhibition andrecovery of photosystem II (PSII) was followed by fluorescence, CO2 exchange, andimmunoblotting analyses. Results: The same reduction (25%) in maximum PSII efficiency (Fv/Fm) was observed in both coldacclimated(CA) and non-acclimated (NA) plants under PhT. A full recovery was observed inCA plants of both ecotypes under dark conditions, but CA Antarctic plants recover faster thanthe Andean ecotype.Under PhT, CA plants maintain its quantum yield of PSII, while NA plants reduced itstrongly (50% and 73% for Andean and Antarctic plants respectively). Cold acclimationinduced the maintenance of PsaA and Cyt b6/f and reduced a 41% the excitation pressure inAntarctic plants, exhibiting the lowest level under PhT. Cold acclimation decreasessignificantly NPQs in both ecotypes, and reduce chlorophylls and D1 degradation in Andeanplants under PhT.NA and CA plants were able to fully restore their normal photosynthesis, while CA Antarcticplants reached 50% higher photosynthetic rates after recovery, which was associated toelectron fluxes maintenance under photoinhibitory conditions. Conclusions: Cold acclimation has a greater importance on the recovery process than on limitingphotodamage. Cold acclimation determined the kinetic and extent of recovery process underdarkness in both C. quitensis ecotypes. The greater recovery of PSII at low temperature in theAntarctic ecotype was related with its ability to maintain PsaA, Cyt b6/f and D1 protein afterphotoinhibitory conditions. This is probably due to either a higher stability of thesepolypeptides or to the maintenance of their turnover upon cold acclimation. In both cases, itis associated to the maintenance of electron drainage from the intersystem pool, whichmaintains QA more oxidized and may allow the synthesis of ATP and NADPH necessariesfor the regeneration of ribulose 1,5-bisphosphate in the Calvin Cycle. This could be a keyfactor for C. quitensis success under the harsh conditions and the short growing period in theMaritime Antarctic.
Electronic ISSN:
1471-2229
Topics:
Biology
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