B3.4: Function of cuticular waxes in plant response to wounding

Ivo Feussner & Harry Brumer

The plant surface is covered with a waxy cuticle that serves as a first structural and chemical barrier against abiotic and biotic stresses (Resemann et al., 2019; Samuels et al., 2008). It consists of two different types of lipophilic materials, cutin and cuticular wax. Cuticular wax is a mixture of highly hydrophobic monomers derived from saturated very long chain fatty acids (VLCFAs) with predominant chain lengths from C26 to C34. VLCFAs are used for the production of wax components (aldehydes, alcohols, alkanes, ketones, and alkyl esters) via two wax biosynthetic pathways: an alcohol-forming pathway and an alkane-forming pathway. While knowledge on the alkane-forming pathway is rather incomplete, it is well established for flowering plants that the alcohol-forming pathway consists of two reactions: the fatty acyl-CoA reductase and the wax synthase. However, similar cuticular wax compositions in a wide variety of plant species suggest that cuticle structure and formation are highly conserved across the plant kingdom.

Even though most of the steps involved in the formation of cuticular wax components are known, and representative genes encoding the enzymes have been cloned from flowering plants, it is not clear when cutin formation evolved during plants water-to-land-transition. In particular, knowledge on the specific roles and the relative importance of individual molecular classes in biotic and abiotic plant stress biology is scarce. Therefore, we will examine the biosynthesis and role of cutin and cuticular wax in plant defense and upon drought stress in the bryophytes Marchantia polymorpha and Physcomitrium patens.

References
Resemann, H.C., M. Lewandowska, J. Gömann, and I. Feussner: Membrane lipids, waxes and oxylipins in the moss model organism Physcomitrella patens. Plant Cell Physiol. 60, 1166-1175 (2019).
Samuels, L., L. Kunst, and R. Jetter: Sealing plant surfaces: Cuticular wax formation by epidermal cells. Annu. Rev. Plant Biol. 59, 683-707 (2008).