DsCER26 Affects the Leaf Dehydration Tolerance of Rice by Altering Cuticular Wax Alkane Production without Affecting the Grain Fatty Acid Content

Plant aerial organs are covered in cuticular wax, which plays an important role in response to dehydration stress by limiting non-stomatal water loss. Cuticular wax is a complex mixture of very-long-chain fatty acids (VLCFAs) with chain lengths ranging from 20 to 34 carbons (C) and their derivatives. Research suggests that the ECERIFERUM2-like (CER2-like) proteins in Arabidopsis and rice are involved in the biosynthesis of the wax composition beyond C24. However, the CER2-like protein function in other plants remains uninvestigated. In the present study, a homologue of rice OsCER2-like/CER26 from a high-wax mutant in Dianthus spiculifolius was identified and named DsCER26. The green fluorescent protein-labeled DsCER26 was localized in the endoplasmic reticulum, and it interacts with rice β-ketoacyl-CoA synthase 6 (OsKC6/CER6). Under heat stress, the heterologous expression of DsCER26 reduced the water loss rate in transgenic rice leaves compared to the wild-type leaves. Mass spectrometry analysis revealed that a significant increase in the cuticular wax alkanes (mainly the C27 alkane) on the leaves of transgenic rice compared with wild-type leaves. The results suggest that the heterologous expression of DsCER26 may enhance dehydration tolerance in transgenic rice, primarily by increasing the cuticular wax C27 alkane. In addition, the major long-chain fatty acid (C16 and C18) content in transgenic rice grains was not altered. DsCER26 may be a novel genetic resource for improving rice dehydration tolerance without impacting grain nutrition.