DETERMINANTS OF FRUIT CUTICULAR COMPOSITION AND WATER PERMEABILITY IN CULTIVATED TOMATO AND ITS WILD RELATIVES

Supplemental file(s) description: Supplementary data files for Chapter 3, Supplementary data and movie files for Chapter 4, Supplemental Tables 1-3 for Appendix 1In plants, an outer waxy coating, termed the cuticle, serves as the barrier between most above-ground organs and the environment, and is thus thought to have a significant role in protecting the plant from external biotic and abiotic stresses. Considerable progress has been made in uncovering genes involved in the biosynthesis of cuticular components; however, much remains to be learnt about the relationship between cuticle composition, structure and function. In particular, a longstanding question is the identity of the factors underlying cuticle water permeance and its wide variation across species. The research presented here leveraged the cuticle diversity found amongst domesticated tomato (Solanum lycopersicum) cultivars and their wild relatives to investigate the associations between different cuticle properties, as well as the genetic underpinnings of their variation. Through the use of homology analysis, genetic mapping and transcriptomics, S. lycopersicum was compared with the wild species S. pennellii and S. neorickii to identify the genetic differences responsible for their distinct cuticle properties. Furthermore drought stress was shown to alter the composition of the fruit cuticles of each of these species differently, but did not substantially alter the water permeance values of any of them. Characterization of S. lycopersicum cultivars with particularly high or low fruit transpiration rates revealed that the cuticular water permeance was mainly a product of the abundance of trichome-associated transcuticular pores. This body of work advances our understanding of the mechanisms by which cuticle properties are determined and identifies possible avenues for breeding or engineering to improve fruit shelf life