Professor University of California Davis Davis, California
Crop plants often experience episodic stress in the field leading to economic and environmental losses, however, sustained, anthropogenic stress imposed on the harvested parts of horticultural crops during storage, also leads to food loss but has been given relatively little attention. Post-harvest stresses, like chilling, were designed to slow-down, pause, or halt biological processes to extend organ storage life, but they often unintentionally, disrupt the intrinsic physiological processes in the organ resulting in poor quality or even accelerated senescence. This phenomenon called postharvest chilling injury (PCI), affects plant species that originated from tropical regions, at all stages of their lifecycle. In my presentation I will describe our three approaches to studying PCI in tomato. First, we examined the spatio-temporal development of biophysical changes in fruit in response to chilling. Second, we are genetically engineering fruit using promoters that would induce or otherwise change the expression of select genes in fruit under cold storage to determine their effect on fruit quality. We have focused on two transcription factors that are both responsive to chilling and ripening. We used a chemical- and a stress-inducible promoter to artificially promote CBF1 expression, and in a distinct approach, we are editing the promoter of the RIN gene, to create tomato lines varying incrementally in RIN expression. Third, to understand how early harvest and low temperature storage influence the quality of fruit at the molecular level, we are examining the methylome and transcriptome of different batches of fruit harvested green and ripened at different temperatures. Low temperature not only influences fruit ripening quality, but causes a disconnect between physiological and chronological age. How the transcriptomic and methylomic networks correlate with fruit biochemical parameters, may reveal pathways and regulatory steps important in defining quality in stored fruit. The results of these on-going projects will be discussed.