Transcriptional responses underlying physiological stress responses in tomato and a subset of its wild relatives

摘要

Understanding environmental stress responses in crop plants is becoming of greater importance as the population grows to the projected 9 billion by the year 2050. This will require that we develop stress resilient crop cultivars to maintain high yields using fewer key resources such as land and nutrients and expand arable land into salinized soil. In this work, tomato and selected wild relatives are used to understand the genetic basis of complex physiological responses to light competition, limitations to Nitrogen (N) or Phosphorus, and salt stress.;Growing plants in crowded stands is known to induce a light competition response known as the shade avoidance response (SAR) in many species including tomato. The SAR is perceived by alterations in the ambient light spectra and is particularly depleted in red light and enriched in far-red light. Physiologically, the SAR is classically characterized by elongation of the internodes and petioles at the expense of biomass production. Though the SAR is an adaptive strategy used to outcompete its neighbors, this can be unfavorable in an agricultural context. To further attenuate the SAR in tomato, the genetic basis for such a response must be understood. A quantitative trait loci (QTL) mapping approach allowed for the identification of genotypes that either had an increased or decreased elongation SAR. Transcriptomic analysis of the QTL mapping population showed that genotypes with heightened or attenuated sensitivity had altered expression patterns of several auxin related genes. Quantification of auxin confirmed that auxin production is altered under shade in the extreme genotypes. This work suggests that the hormone auxin may play a key role in the SAR in tomato.;Other abiotic stressors such as limitation of N or P and exposure to high salinity are known to reduce photosynthetic capacity and therefore contribute to loss in yield. One means towards breeding for stress resilient cultivars is to utilize the germplasm of wild crop relatives that have demonstrated resistance or favorable physiological adaptations to withstand sub-optimal growth conditions. While leaf-level gas exchange measurements showed that the wild relatives responded similarly to N or P withdrawal, the species showed a divergence in their response to salt stress. In particular, this approach provided insight into variation of physiological mechanisms in place to cope with an applied stress.;To better understand the genetic underpinnings of physiological adaptations to N, P or salt stress, a transcriptomics approach was utilized. This allowed for the deeper understanding of how distantly related species can achieve similar physiological responses, yet arrive to such states by utilizing similar and distinct genetic and metabolic pathways.