94 pages ; The ability to synthesize, deposit and maintain a biomechanically resilient epidermis and a hydrophobic cuticle covering aerial organs are crucial protective features of all land plants. To achieve an intact and dynamic epidermal layer in growing tissues, the deposition of complex primary cell wall polysaccharides and structural cuticular lipids must involve complex and coordinated trafficking, assembly, and restructuring processes. In rapidly expanding organs, such as fleshy fruits, lack of coordination of these processes can result in cuticle and epidermal defects, manifested as cracking and corky scarring, which in crops can lead to substantial economic losses. Identification of the causes of such defects can also provide new insights into the molecular basis of systems to maintain epidermal integrity. As an example, the tomato HYPERCRACKING 1 (hcr1) mutant shows extensive fruit cracking at an early developmental stage, and consequent massive deposition of suberin in the epidermis during growth. Map-based cloning of the hcr1 locus and biochemical analysis suggested that the hyper-cracking phenotype is a consequence of defective sterol biosynthesis. Morphological, cytological, and molecular characterization of hcr1 fruit revealed inhibited cell expansion and division in the pericarp and reduced cellulose levels leading to impaired pericarp development, resulting in uncoordinated expansion between the pericarp and the inner tissues leading to cracking. This study suggests that sterols are important for primary cell wall deposition, and notably cellulose synthesis. Moreover, the presence of a strong cracking phenotype in fruit, but not vegetative tissues, highlights variability in the susceptibility of different organs to impaired epidermal integrity.Relatedly, a second study is concerned with microscopic pores associated with trichomes on the fruit cuticle that are exposed when trichomes are dislodged. Staining of the pore areas with Toluidine Blue has shown that they have the capacity to become ...