EIN2L, EIL3, and EIL4 Modulates Drought Resistance and Growth by Regulating Stomatal Movement in Soybean

Soybean (Glycine max) is a globally important crop for oil, grain and feed; however, drought stress limits its yield and quality. Ethylene alters plant development, stress responses and yield, but the molecular mechanism(s) by which it regulates these processes have not been fully elucidated. Here we show the regulatory factors EIN2L, EIL3, and EIL4 modulate stomatal movement and drought induced-ABA response. Plants with a triple EIN2L, EIL3, and EIL4 CRISPR/Cas9 knockout showed attenuated darkness, ABA- and ethylene-mediated stomatal closure, with altered expression of genes related to ROS, NO and the anionic channels SLAHs. Furthermore, EIN2L, EIL3, and EIL4 regulators positively regulate ethylene synthesis genes (ACS and ACO) during darkness and ABA synthesis (NCED3) and sensitivity (PYL8) genes following ABA treatment. Higher photosynthesis of well-watered plants and stomatal opening of the knockout line, along with its diminished sensitivity to ABA, enhanced water use thereby increasing sensitivity to drought. Selecting for allelic variation in EIN2L, EIL3, and EIL4 genes could better adapt soybean cultivars to the prevailing soil water availability, according to whether water conserving (WT alleles) or water-spending (knockout lines) traits enhance crop yields.