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
Volume262
Early online date21 May 2021
DOIs
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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