Ph.D. Candidate University of California, Davis Davis, California
Body of Abstract: Low-temperature storage and early harvesting of fruit are commonly used to slow down tomato fruit ripening for commercial sale, however, these treatments may be perceived as stressors, and they negatively affect fruit quality leading to fruit loss/waste. My work aims to (1) uncover the molecular underpinnings of how fruit handling, i.e., postharvest stress induces alterations in fruit quality, and (2) fine-tune the expression of a master ripening regulator- the RIN gene which is suppressed in cold, to modify fruit ripening speed and possibly, expression under low temperatures. Our first aim establishes the postharvest fruit physiological state (quality), fruit methylome by WGBS, and fruit transcriptome by RNASeq, to understand the dynamics of DNA methylation, gene expression, and their effects on fruit quality. The results shown postharvest fruit ripened to the ‘Turning’ stage under different storage treatments had lower quality than freshly harvested Turning (FHT) fruit. Remarkably, this was in accordance with our fruit methylome and transcriptome data, as the PCA plots had similar patterns. Functional analysis of the differentially expressed and methylated genes collectively indicated that photosynthetic pathways were enriched in FHT fruit, and this could be associated with reduced chlorophyll contents in our stored fruit. Network analyses of integrated fruit physiology, i.e., ABA and carotenoids contents, ethylene, etc., and muti-omics data are done to identify the regulation of fruit quality under postharvest stress. Secondly, the upstream region of the RIN gene was targeted by CRISPR/Cas9 multiplexed editing directed to potential TF-binding and differentially methylated regions. Preliminary identification of RIN mutations of the 100+ regenerated lines, assessment of RIN transcriptional levels, and the characteristics of ripening fruit are ongoing. Together these data could improve the interpretation of how tomato fruit ripening patterns are altered by postharvest practices and how variable changes in RIN expression levels possibly alter fruit ripening and quality.