Cutin: Xyloglucan transacylase (CXT) activity covalently links cutin to a plant cell-wall polysaccharide

Anzhou Xin, Stephen C. Fry

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

The shoot epidermal cell wall in land-plants is associated with a polyester, cutin, which controls water loss and possibly organ expansion. Covalent bonds between cutin and its neighbouring cell-wall polysaccharides have long been proposed. However, the lack of biochemical evidence makes cutin–polysaccharide linkages largely conjectural. Here we optimised a portfolio of radiochemical assays to look for cutin–polysaccharide ester bonds in the epidermis of pea epicotyls, ice-plant leaves and tomato fruits, based on the hypothesis that a transacylase remodels cutin in a similar fashion to cutin synthase and cutin:cutin transacylase activities. Through in-situ enzyme assays and chemical degradations coupled with chromatographic analysis of the 3H-labelled products, we observed that among several wall-related oligosaccharides tested, only a xyloglucan oligosaccharide ([3H]XXXGol) could acquire ester-bonds from endogenous cutin, suggesting a cutin:xyloglucan transacylase (CXT). CXT activity was heat-labile, time-dependent, and maximal at near-neutral pH values. In-situ CXT activity peaked in nearly fully expanded tomato fruits and ice-plant leaves. CXT activity positively correlated with organ growth rate, suggesting that it contributes to epidermal integrity during rapid expansion. This study uncovers hitherto unappreciated re-structuring processes in the plant epidermis and provides a step towards the identification of CXT and its engineering for biotechnological applications.
Original languageEnglish
Article number153446
Number of pages39
JournalJournal of Plant Physiology
Early online date21 May 2021
Publication statusPublished - 1 Jul 2021

Keywords / Materials (for Non-textual outputs)

  • epidermis remodelling
  • cutin
  • xyloglucan
  • ester bond
  • transacylase
  • cell expansion
  • polyester-polysaccharide conjugates


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