Synthesis and Oligomerization of 10,16‐Dihydroxyhexadecanoyl Esters with Different Head‐Groups for the Study of CUS1 Selectivity

Abstract

Members of the CUS family, suspected to be responsible for cutin polymerization, have shown in vitro activity towards sn‐2 glyceryl ester (2‐MAGs). To assess the selectivity of CUS enzymes towards esters with different headgroups, the CUS1 mediated in vitro polymerization of four monomers of 10,16‐dihydroxyhexadecanoic acid was investigated. Our results demonstrated that CUS1 is more selective towards sn‐2 glyceryl ester, reinforcing the hypothesis that 2‐MAGs are the monomeric precursors of the plant polyester cutin. Additionally, the absence of oxygen atoms in the headgroup negatively impacts the efficiency of polymerization.

Cutin:cutin-acid endo-transacylase (CCT), a cuticle-remodelling enzyme activity in the plant epidermis

“…The only well-studied cutin transacylase in the apoplast, tomato CUS1 [ 13 , 26 , 66 ], has a pH optimum similar to that of the observed CCT activity ( Figure 3a ). As a GDSL protein [ 67 ], CUS1 may be promiscuous with respect to its substrate specificity.…”

“…As a GDSL protein [ 67 ], CUS1 may be promiscuous with respect to its substrate specificity. We therefore investigated CUS1 as a candidate possibly responsible for CCT activity despite the non-involvement of CUS1's only known donor substrates (HFA-glycerols) [ 13 , 66 ] in the CCT assay. In in-situ assays, cus1 mutant tomato fruit epidermis exhibited as much CCT activity as the wild-type (cv.…”

Cutinsomes and CUTIN SYNTHASE1 Function Sequentially in Tomato Fruit Cutin Deposition

“…CUS1 is a GDSL lipase/hydrolase protein located to the cutinized OEW of tomato fruit that has been postulated to play an important role in cutin synthesis (Girard et al, 2012;Yeats et al, 2012). Although its mechanism of action and substrate recognition is still undetermined, in vitro analysis of CUS1 activity has delivered linear oligomers with up to six fatty acid units (Yeats et al, 2014;San Segundo et al, 2019). Results presented herein displayed a good correlation between CUS1 immunolocalization and gene expression.…”

Mini Review: Transport of Hydrophobic Polymers Into the Plant Apoplast

“…Recently, a full-size transporter, AtABCG32, was reported to contribute to cuticle formation because knockout mutants exhibit slightly less cutin deposition in leaves ( Fabre et al, 2016 ). Authors emphasized that the exact function of ABCG32 remains vague because there is no evidence for it to be indeed required for exporting 2-monoacylglycerols, the only verified cutin precursor type ( Yeats et al, 2012 ; San Segundo et al, 2019 ). The same applies to AtABCG11 and 13.…”