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ARS Home » Midwest Area » Urbana, Illinois » Global Change and Photosynthesis Research » Research » Publications at this Location » Publication #330142

Title: Physiological evidence for plasticity in glycolate/glycerate transport during photorespiration

Author
item Walker, Berkley
item South, Paul
item Ort, Donald

Submitted to: Photosynthesis Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2016
Publication Date: 6/1/2016
Citation: Walker, B.J., South, P.F., Ort, D.R. 2016. Physiological evidence for plasticity in glycolate/glycerate transport during photorespiration. Photosynthesis Research. 129:93-103.

Interpretive Summary: Gross CO2 assimilation during photosynthesis is diminished by CO2 loss from photorespiration in C3 plants. This CO2 loss is dependent on temperature and CO2 concentration and comprises the largest single loss of carbon to an illuminated C3 leaf, resulting in an annual decrease of>300 trillion dietary calories in the Midwestern United States alone. This work revealed that more than one glycolate export pathway is present in chloroplast envelope membranes. These findings indicate that photorespiration is plastic in transport processes and suggest mechanism for the regulation of photosynthesis by photorespiration.

Technical Abstract: Photorespiration recycles fixed carbon following the oxygenation reaction of Ribulose, 1–5, carboxylase oxygenase (Rubisco). The recycling of photorespiratory C2 to C3 intermediates is not perfectly efficient and reduces photosynthesis in C3 plants. Recently, a plastidic lycolate/ glycerate transporter (PLGG1) in photorespiration was identified in Arabidopsis thaliana, but it is not known how critical this transporter is for maintaining photorespiratory efficiency. We examined a mutant deficient in PLGG1 (plgg1-1) using modeling, gas exchange, and Rubisco biochemistry. Under low light, there was no difference in the quantum efficiency of CO2 assimilation or in the photorespiratory CO2 compensation point of plgg1-1, indicating that photorespiration proceeded with wild-type efficiency under sub-saturating light irradiances. Under saturating light irradiance, plgg1-1 showed decreased CO2 assimilation that was explained by decreases in the maximum rate of Rubisco carboxylation and photosynthetic linear electron transport. Decreased rates of Rubisco carboxylation resulted from probable decreases in the Rubisco activation state. These results suggest that glycolate/ glycerate transport during photorespiration can proceed in moderate rates through an alternative transport process with wild-type efficiencies. These findings also suggest that decreases in net CO2 assimilation that occur due to disruption to photorespiration can occur by decreases in Rubisco activity and not necessarily decreases in the recycling efficiency of photorespiration.