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The chloroplastic UGT72A2 glycosylating naringenin is involved in leaf redox homeostasis in poplar

par Behr, Marc ;Speeckaert, Nathanaël ;Kurze, Elisabeth KE;Prévost, Martine ;Schwab, Wilfried;El Jaziri, Mondher ;Baucher, Marie
Référence 2021 International Conference on Plant Systems Biology and Biotechnology (14-17/06/2021: Varna, Bulgarie)
Publication Non publié, 2021-06-16

Communication à un colloque

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Résumé :

Flavonoids scavenge reactive species produced during photosynthesis and protect plant cells against deleterious oxidative damages. Their biosynthesis and conjugations are therefore under tight homeostasis at several levels. Glycosylation modifies the subcellular repartition of these metabolites, regulating the flux of their formation. This contribution presents a functional analysis of a poplar chloroplastic UDP-glycosyltransferase (UGT) involved in the homeostasis of flavonoids. Recombinant UGT72A2 specifically glucosylates naringenin, a flavanone precursor of most other flavonoids. Molecular docking of UGT72A2 with various flavonoids highlights key residues interacting with UDP-glucose and naringenin, paving the way for future targeted mutagenesis. UGT72A2 is trans-activated by flavonoid regulators MYB119 and TT8. Leaves of transgenic poplar lines with reduced expression of UGT72A2 are characterised by necrosis and premature abscission typical of oxidative damages under standard growing conditions. Lower pool of phenolics and flavonoids, lower soluble peroxidase activity and impaired homeostasis of NADPH and NADP+ pools in the leaves of RNAi lines reflect the decreased efficiency of systems scavenging reactive species. Poplar lines overexpressing UGT72A2 accumulate more phenolics and flavonoids. Finally, leaves of RNAi lines are less sensitive to oxidative stress caused by methyl viologen, which may suggest a retrograde signalling from damaged chloroplasts to mitigate the consequences of deficient redox homeostasis. This study highlights naringenin glucosylation as a metabolic node in the biosynthesis of flavonoids and points to its important role in buffering redox status under standard growing conditions in poplar.