Competing carboxylases: circadian and metabolic regulation of Rubisco in C3 and CAM Mesembryanthemum crystallinum L.

作者：Davies B N; Griffiths H^*

来源：Plant, Cell and Environment, 2012, 35(7): 1211-1220.

DOI：10.1111/j.1365-3040.2012.02483.x

• Carbon isotope discrimination
• continuous light
• crassulacean acid metabolism (CAM)
• PEPc

The temporal co-ordination of ribulose 1 center dot 5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPc) activities by Mesembryanthemum crystallinum L. in C3 and crassulacean acid metabolism (CAM) modes was investigated under conventional light-dark (LD) and continuous light (LL) conditions. When C3, net CO2 assimilation rate increased during each subjective night under LL with maximum carboxylation unrelated to Rubisco activation state. The CAM circadian rhythm of CO2 uptake was more pronounced, with CO2 assimilation rate maximal towards the end of each subjective night. In vivo and in vitro techniques were integrated to map carboxylase enzyme regulation to the framework provided by CAM LL gas exchange activity. Rubisco was activated in vitro throughout each subjective dark period and consistently deactivated at each subjective dawn, similar to that observed at true dawn in constitutive CAM species. Instantaneous carbon isotope discrimination showed in vivo carboxylase co-dominance during the CAM subjective night, initially by Rubisco and latterly C4 (PEPc), despite both enzymes seemingly activated in vitro. The circadian rhythm in titratable acidity accumulation was progressively damped over successive subjective nights, but maintenance of PEPc carboxylation capacity ensures that CAM plants do not become progressively more C3-like with time under LL.

• 出版日期2012-7