Positive regulatory role of strigolactone in plant responses to drought and salt stress

This report provides direct evidence that strigolactone (SL) positively regulates drought and high salinity responses in Arabidop-sis. Both SL-deficient and SL-response [more axillary growth (max)]mutants exhibited hypersensitivity to drought and salt stress,which was associated with shoot- rather than root-related traits.Exogenous SL treatment rescued the drought-sensitive phenotypeof the SL-deficient mutants but not of the SL-response mutant,and enhanced drought tolerance of WT plants, confirming the roleof SL as a positive regulator in stress response. In agreement withthe drought-sensitive phenotype, maxmutants exhibited increasedleaf stomatal density relative to WT and slower abscisic acid (ABA)-induced stomatal closure. Compared with WT, the max mutantsexhibited increased leaf water loss rate during dehydration anddecreased ABA responsiveness during germination and postgermi-nation. Collectively, these results indicate that cross-talk betweenSL and ABA plays an important role in integrating stress signals toregulate stomatal development and function. Additionally, a comparative microarray analysis of the leaves of the SL-response max2mutant and WT plants under normal and dehydrative conditionsrevealed an SL-mediated network controlling plant responses tostress via many stress- and/or ABA-responsive and cytokinin metabolism-related genes. Our results demonstrate that plants integrate multiple hormone-response pathways for adaptation toenvironmental stress. Based on our results, genetic modulation ofSL content/response could be applied as a potential approach toreduce the negative impact of abiotic stress on crop productivity.