Genetic variation and the response to abiotic stress in cultivated sunflower (helianthus annuus l.) seedlings
Masalia, Rishi R.
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As sessile organisms, plants are exposed to numerous environmental stresses during their lifetimes. These include challenges related to drought, salinity, and low nutrient availability, all of which can negatively impact plant growth and development and reduce crop yields. Currently, drought and nutrient limitation are offset through increased irrigation and fertilizer application, however, these agricultural inputs are environmentally, economically, and energetically costly. Moreover, irrigation can lead to soil salinization. Attention has thus turned to the development of increasingly resilient crops, but such efforts require knowledge of the mechanistic basis of variation in growth and performance under stress. Here, I describe research aimed at characterizing genetic variation underlying seedling growth traits in cultivated sunflower (Helianthus annuus L.) under well-watered and water-limited (i.e., osmotic stress), as well as the phenotypic and transcriptomic response of such seedlings to multiple water-related stresses as well as nutrient limitation. Genome-wide association studies revealed that cultivated sunflower harbors substantial variation for seedling growth and root-related traits under both well-watered and water-limited conditions, with evidence that many of the significantly associated regions had consistent effects across environments. Moreover, the transcriptomic response to water-related stresses (drought, osmotic, and salt), revealed that over 30% (502/1332) of differentially expressed genes (DEGs) were shared between at least two stresses, with 51 DEGs shared across all three stresses, in either leaf or root tissue. There was an overall bias toward up-regulation of DEGs, particularly in roots, and there were substantially more DEGs in roots vs. leaves. All 51 of the DEGs shared across these three stresses exhibited a common direction of response, and this pattern held for the subset of 26 DEGs that were also shared with low nutrient stress. Under nutrient stress, however, there were substantially more DEGs in leaves vs. roots, though there was a similar bias toward up-regulation. Taken together, these results add to a growing body of data on the genetic basis of phenotypic variation under stress, as well as the phenotypic and transcriptomic response of plants to a variety of abiotic stresses.