Solving the puzzles of cutin and suberin polymer biosynthesis

Cutin and suberin are insoluble lipid polymers that provide critical barrier functions to the cell wall of certain plant tissues, including the epidermis, endodermis and periderm. Genes that are specific to the biosynthesis of cutins and/or aliphatic suberins have been identified, mainly in Arabidopsis thaliana. They notably encode acyltransferases, oxidases and transporters, which may have either well-defined or more debatable biochemical functions. However, despite these advances, important aspects of cutin and suberin synthesis remain obscure. Central questions include whether fatty acyl monomers or oligomers are exported, and the extent of extracellular assembly and attachment to the cell wall. These issues are reviewed. Greater emphasis on chemistry and biochemistry will be required to solve these unknowns and link structure with function.

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► Biosynthesis of polyesters require various hydroxylases and acyltransferases.
► Many Arabidopsis mutants impaired in a biosynthetic step are now available.
► GPAT acyltransferases have a unique sn-2 specificity and phosphatase activity.
► Monoacylglycerols are implicated intermediates in polyester assembly.
► The extra-cellular or intra-cellular site of fatty acid polymerization is still unknown.