Glyceraldehyde-3-phosphate dehydrogenase subunits A and B are essential to maintain photosynthetic efficiency

Simkin, A. J., Alqurashi, M., Lopez-Calcagno, P. E., Headland, L. R. and Raines, C. A. (2023) Glyceraldehyde-3-phosphate dehydrogenase subunits A and B are essential to maintain photosynthetic efficiency. Plant Physiology, (doi: 10.1093/plphys/kiad256) (PMID:37099455) (Early Online Publication)

Abstract

In plants, glyceraldehyde-3-phosphate dehydrogenase (GAPDH; EC 1.2.1.12) reversibly converts 1,3-bisphosphoglycerate to glyceraldehyde-3-phosphate coupled with the reduction of NADPH to NADP + . The GAPDH enzyme that functions in the Calvin Benson Cycle is assembled either from four glyceraldehyde-3-phosphate dehydrogenase A subunits (GAPA) proteins forming a homotetramer (A4) or from two GAPA and two glyceraldehyde-3-phosphate dehydrogenase B subunit (GAPB) proteins forming a heterotetramer (A2B2). The relative importance of these two forms of GAPDH in determining the rate of photosynthesis is unknown. To address this question, we measured the photosynthetic rates of Arabidopsis (Arabidopsis thaliana) plants containing reduced amounts of the GAPDH A and B subunits individually and jointly, using T-DNA insertion lines of GAPA and GAPB and transgenic GAPA and GAPB plants with reduced levels of these proteins. Here we show that decreasing the levels of either the A or B subunits decreased the maximum efficiency of CO2 fixation, plant growth, and final biomass. Finally, these data showed that the reduction in GAPA protein to 9% wild-type levels resulted in a 73% decrease in carbon assimilation rates. In contrast, eliminating GAPB protein resulted in a 40% reduction in assimilation rates. This work demonstrates that the GAPA homotetramer can compensate for the loss of GAPB, whereas GAPB alone cannot compensate fully for the loss of the GAPA subunit.

• Item Type: Articles
• Additional Information: A.J.S, P.E.L.C and L.H were supported by BBSRC (Grant: BB/J004138/1 awarded to C.A.R). M.A was funded by the Saudi Arabian Government and by the University of Essex Research Incentive Scheme to C.A.R. A.J.S is supported by the Growing Kent and Medway Program, UK; Ref 107139.
• Status: Early Online Publication
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Headland, Dr Lauren
• Authors: Simkin, A. J., Alqurashi, M., Lopez-Calcagno, P. E., Headland, L. R., and Raines, C. A.
• College/School: College of Medical Veterinary and Life Sciences > School of Molecular Biosciences
• Journal Name: Plant Physiology
• Publisher: Oxford University Press
• ISSN: 0032-0889
• ISSN (Online): 1532-2548
• Published Online: 26 April 2023
• Copyright Holders: Copyright © 2023 The Authors
• First Published: First published in Plant Physiology 2023
• Publisher Policy: Reproduced under a Creative Commons License