Enzymatic Penetration of the Plant Cuticle by Fungal Pathogens

TLDR: This chapter shall review recent advances in understanding the nature of the barrier layers and the mechanism of fungal penetration of such barriers, and indicates that the soluble waxes associated with the polymers can play a significant role in the host-pathogen interaction.

Abstract: Cuticle and suberized periderm form barriers that protect plants against ingress by pathogens. The entry of bacteria and viruses into plants usually requires wounds , whereas many fungal pathogens can penetrate the intact barriers. The mode of fungal penetration of the cuticular barrier has been a subject of controversy for the better part of a century, as summarized a decade ago in this series (70). The past decade has seen considerable progress in understanding the nature of the barrier layers and the mechanism of fungal penetration of such barriers . In this chapter I shall review these recent advances; earlier studies have been reviewed previously (2, 48, 49, 60, 70). S ince the insoluble polymeric structural components constitute the main physical obstacle to fun­ gal penetration, this review will focus on these polymers. Although there are indications that the soluble waxes associated with the polymers can play a significant role in the host-pathogen interaction, these chemical interactions remain largely unknown and therefore will not be covered in this chapter. Although successful pathogenesis often involves penetration of the pathogen not only through the cuticle but also through the cell wall, this review is confined to the outer barrier.