Confirmation of UGT71L1's role in salicinoid biosynthesis using transgenic rescue and overexpression poplars
Date
2022
Authors
Loland, Megan
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Abstract
Salicinoids are phenolic secondary plant metabolites unique to the family Salicaceae. Their structures and functions as insect defense compounds are well known, but their biosynthetic pathway has yet to be fully understood. Recently, a UDP-glycosyltransferase, UGT71L1 was knocked out in poplar hybrid plants and they were found to have a major unexpected phenotype change including shrunken leaves and dwarfed height. Also, the concentrations of salicinoids were greatly decreased suggesting that UGT71L1 is essential for salicinoid biosynthesis. Here, UGT71L1 rescue plants, which complemented the mutation, were created and demonstrated a return to wildtype phenotype. This confirmed that the sole cause for the phenotype change was the loss of UGT71L1 and not a result of off-target effects of the transformation. UGT71L1 overexpression plants created from wildtype plants demonstrated that high UGT71L1 levels do not directly alter plant morphology, as expected, although the possibility was raised that UGT71L1 could be a limiting factor. Chemical analysis of the knockout lines suggested the possibility of minor involvement of another glycosylase in the larger salicinoid synthesis pathway. The knockout lines and a partial rescue line contained significantly higher salicylic acid-glucoside (proxy for salicylic acid) concentrations compared to all other lines. Therefore, it was inferred that salicylic acid is likely the cause of phenotypic change and salicylic acid may be linked to the salicinoid pathway. UGT71L1's role in salicinoid biosynthesis is confirmed as crucial, although further research into its effect on salicylic acid and salicin metabolism are necessary in order to advance the understanding of the salicinoid biosynthetic pathway.