Photosynthetic activity in Arabidopsis leaves

28 February 2015 - By: Christine Raines

Photosynthetic activity influences cellulose biosynthesis and phosphorylation of proteins involved therein in Arabidopsis leaves

Tentative summary of plausible events involved in the regulation of synthesis by photosynthesis
Tentative summary of plausible events involved in the regulation of synthesis by photosynthesis, as suggested by phosphopatterns reported in this work, for the photosynthetic case.


 By Christine Raines

J. Exp. Bot. Vol 65, pages 4997-5010. Edouard Boex-Fontvieille, Marlene Davanture, Mathieu Jossier, Michael Zivy, Michael Hodges and Guillaume Tcherkez 


The photosynthetic carbon assimilatory pathway provides intermediates that enter directly into an array of metabolic pathways including starch, sucrose, isoprenoid, shikimate, thiamine and nucleotide.

The relative flux of carbon to these pathways will change dependent on rates of assimilation and developmental stage of the leaf. We still do not have a complete understanding of the relationships between these pathways and how flux is determined. UDP-glucose is the starting intermediate for cellulose synthesis and this is produced from triosephosphates coming from the photosynthetic carbon assimilation pathway.

Cellulose biosynthesis in plants is a substantial sink for carbon at the ecosystem level, but we do no yet have a full understanding of the process of synthesis of this important molecule. We also know very little about the rate of flux of carbon from photosynthesis to cellulose biosynthesis. This paper provides a novel insight into this process. The novelty of this work is the combined application of gas exchange analysis together with isotopic techniques, metabolite analysis and phosphoproteomics. BoexFontvielle et al measure metabolic flux to cellulose and show that this flux increases with increasing photosynthesis but not necessarily in proportion. Phosphoproteomic analysis revealed that a number of enzymes involved in sugar metabolism, including those in the cellulose synthesis complex are phosphorylated.

The authors propose that the stimulation of cellulose biosynthesis as photosynthesis increases is regulated by phosphorylation of CSI1, CESA1 and CESA enzymes of the cellulose synthesis complexes and of sugar synthesising enzymes. 

 

Category: Plant Biology
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Christine Raines

Christine Raines is a Professor of Plant and Molecular Physiology at the University of Essex as well as being Editor in Chief of the Journal of Experimental Botany. Christine is also a member of the SEB Plant Sections Committee and the SEB Council.