摘要
The photorespiratory pathway or photorespiration is an essential process in oxygenic photosynthetic or- ganisms, which can reduce the efficiency of photosynthetic carbon assimilation and is hence frequently considered as a wasteful process. By comparing the response of the wild-type plants and mutants impaired in photorespiration to a shift in ambient C02 concentrations, we demonstrate that photorespiration also plays a beneficial role during short-term acclimation to reduced C02 availability. The wild-type plants re- sponded with few differentially expressed genes, mostly involved in drought stress, which is likely a conse- quence of enhanced opening of stomata and concomitant water loss upon a shift toward low C02. In contrast, mutants with impaired activity of photorespiratory enzymes were highly stressed and not able to adjust stomatal conductance to reduced external C02 availability. The transcriptional response of mutant plants was congruent, indicating a general reprogramming to deal with the consequences of reduced C02 availability, signaled by enhanced oxygenation of ribulose-l,5-bisphosphate and amplified by the artificially impaired photorespiratory metabolism. Central in this reprogramming was the pro- nounced reallocation of resources from growth processes to stress responses. Taken together, our results indicate that unrestricted photorespiratory metabolism is a prerequisite for rapid physiological acclimation to a reduction in C02 availability.
The photorespiratory pathway or photorespiration is an essential process in oxygenic photosynthetic or- ganisms, which can reduce the efficiency of photosynthetic carbon assimilation and is hence frequently considered as a wasteful process. By comparing the response of the wild-type plants and mutants impaired in photorespiration to a shift in ambient C02 concentrations, we demonstrate that photorespiration also plays a beneficial role during short-term acclimation to reduced C02 availability. The wild-type plants re- sponded with few differentially expressed genes, mostly involved in drought stress, which is likely a conse- quence of enhanced opening of stomata and concomitant water loss upon a shift toward low C02. In contrast, mutants with impaired activity of photorespiratory enzymes were highly stressed and not able to adjust stomatal conductance to reduced external C02 availability. The transcriptional response of mutant plants was congruent, indicating a general reprogramming to deal with the consequences of reduced C02 availability, signaled by enhanced oxygenation of ribulose-l,5-bisphosphate and amplified by the artificially impaired photorespiratory metabolism. Central in this reprogramming was the pro- nounced reallocation of resources from growth processes to stress responses. Taken together, our results indicate that unrestricted photorespiratory metabolism is a prerequisite for rapid physiological acclimation to a reduction in C02 availability.
