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

Anzhou Xin, Yue Fei, Attila Molnar, Stephen C. Fry

Research output: Contribution to journalArticlepeer-review

Abstract

Cutin is a polyester matrix mainly composed of hydroxy-fatty acids that occurs in the cuticles of shoots and root-caps. The cuticle, of which cutin is a major component, protects the plant from biotic and abiotic stresses, and cutin has been postulated to constrain organ expansion. We propose that, to allow cutin restructuring, ester bonds in this net-like polymer can be transiently cleaved and then re-formed (transacylation). Here, using pea epicotyl epidermis as the main model, we first detected a cutin:cutin-fatty acid endo-transacylase (CCT) activity. In-situ assays used endogenous cutin as the donor substrate for endogenous enzymes; the exogenous acceptor substrate was a radiolabelled monomeric cutin-acid, 16-hydroxy-[3H]hexadecanoic acid (HHA). High-molecular-weight cutin became ester-bonded to intact [3H]HHA molecules, which thereby became unextractable except by ester-hydrolysing alkalis. In-situ CCT activity correlated with growth rate in Hylotelephium leaves and tomato fruits, suggesting a role in loosening the outer epidermal wall during organ growth. The only well-defined cutin transacylase in the apoplast, CUS1 (a tomato cutin synthase), when produced in transgenic tobacco, lacked CCT activity. This finding provides a reference for future CCT protein identification, which can adopt our sensitive enzyme assay to screen other CUS1-related enzymes.
Original languageEnglish
Article numberBCJ20200835
Pages (from-to)777-798
Number of pages21
JournalBiochemical Journal
Volume478
Issue number4
Early online date24 Feb 2021
DOIs
Publication statusE-pub ahead of print - 24 Feb 2021

Keywords

  • plant epidermis
  • cuticle
  • curtin re-modelling
  • transacylase activity
  • cell expansion
  • pea epicotyl

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