Search

Climate change can alter precipitation patterns, disrupting the natural water cycle and generating drought periods that negatively impact crop yield or plant survival. Novel biotechnological approaches are being developed to face water deficits. Specifically, molecular knowledge of the plant hormone abscisic acid (ABA) can be harnessed to develop genetic and chemical approaches to cope with abiotic stress. ABA receptor agonists are promising molecules that activate ABA signaling on demand and show long-lasting effects, in contrast to the exogenous application of ABA, which has a short half-life. In this work, we studied the effect of the iSB09 agonist on tomato plants grown under drought stress or well-watered conditions. iSB09 treatment induced stomatal closure in tomato through activation of PYL1-like and PYL4-like ABA receptors. Additionally, RNA-seq analyses reveal coordinated upregulation by ABA or iSB09 of the genes encoding enzymes involved in the synthesis of the osmoprotective galactinol and raffinose family of oligosaccharides. Foliar spraying of iSB09 under drought conditions anticipated the regulation of transpiration, promoted drought avoidance and increased water use efficiency in tomato plants. Physiological analysis of agonist-treated plants reveals increased CO2 assimilation and effective quantum yield of the photosystem II under drought conditions in iSB09-treated plants compared to mock-treated. Faster regulation of transpiration at the start of the drought period was achieved by iSB09 treatment, and, as a result, water consumption was reduced compared to mock-treated plants. Overall, the agonist treatment mounts the genome-wide transcriptional response to stress and increases water use efficiency under drought conditions and plant protection.

To face the challenges of climate change and sustainable food production, it is essential to develop crop genome editing techniques to pinpoint key genes involved in abiotic stress signaling. The identification of those prevailing abscisic acid (ABA) receptors that mediate plant-environment interactions is quite challenging in polyploid plants because of the high number of genes in the PYR/PYL/RCAR ABA receptor family. Nicotiana benthamiana is a biotechnological crop amenable to genome editing, and given the importance of ABA signaling in coping with drought stress, we initiated the analysis of its 23-member family of ABA receptors through multiplex CRISPR/Cas9-mediated editing. We generated several high-order mutants impaired in NbPYL1-like and NbPYL8-like receptors, which showed certain insensitivity to ABA for inhibition of seedling establishment, growth, and development of shoot and lateral roots as well as reduced sensitivity to the PYL1-agonist cyanabactin (CB). However, in these high-order mutants, regulation of transpiration was not affected and was responsive to ABA treatment. This reveals a robust and redundant control of transpiration in this allotetraploid plant that probably reflects its origin from the extreme habitat of central Australia.