ZmSRL5is involved in drought tolerance by maintaining cuticular wax structure in maize

Cuticular wax is a natural barrier on terrestrial plant organs, which protects plants from damages caused by a variety of stresses. Here, we report the identification and functional characterization of a cuticular-wax-related gene,Zea maysL.SEMI-ROLLED LEAF 5(ZmSRL5). The loss-of-function mutantsrl5, which was created by a 3,745 bp insertion in the first intron that led to the premature transcript, exhibited abnormal wax crystal morphology and distribution, which, in turn, caused the pleiotropic phenotypes including increased chlorophyll leaching and water loss rate, decreased leaf temperature, sensitivity to drought, as well as semi-rolled mature leaves. However, total wax amounts showed no significant difference between wild type andsemi-rolled leaf5 (srl5)mutant. The phenotype ofsrl5was confirmed through the generation of two allelic mutants using CRISPR/Cas9.ZmSRL5encodes a CASPARIAN-STRIP-MEMBRANE-DOMAIN-LIKE (CASPL) protein located in plasma membrane, and highly expressed in developing leaves. Further analysis showed that the expressions of the most wax related genes were not affected or slightly altered insrl5. This study, thus, primarily uncovers thatZmSRL5is required for the structure formation of the cuticular wax and could increase the drought tolerance by maintaining the proper cuticular wax structure in maize.