Understanding Cuticle Development in Tomato through the Study of Novel Germplasm with Malformed Cuticles

Plant cuticle development and metabolism are still poorly understood, partly due to the chemical complexity of the cuticular layer. The overall research objective was to broaden and deepen our understanding of tomato fruit cuticle development by analyzing novel germplasm with cuticular malformations and by studying the transcriptome and proteome of the fruit epidermal tissues, as strategies to overcome the challenges posed by the recalcitrance of the biological system. During the project we succeeded in identifying two genes with major impact on cuticle development. One of these encoded the first cutin synthase to be identified in plants, a metabolic step that had been a black box in cutin synthesis. In addition genes controlling the triterpenoid components of the cuticle were identified and, most interestingly, genetic variability for this component was identified among the wild tomato species germplasm. Additional germplasm was developed based on interspecific crosses that will allow for the future characterization of modifier genes that interact with the microfissuring gene (CWP) to promote or inhibit fruit cracking. One of the major accomplishments of the joint project was the integrated transcriptomic and proteomic analysis of the fruit cuticle and underlying tissues which allows for the identification of the pericarp cell layers responsible for the extracellular, cuticle-localized protein component. The results of the project have expanded our understanding of tomato fruit cuticle development and its genetic control. In addition, germplasm developed will be useful in developing tomato varieties resistant to cracking, on the one hand, and varieties useful for the dehydration industry on the other.