Identification and expression analyses of O-acyltransferase WSD genes in Rehmannia glutinosa

Plant wax ester synthase catalyzes the synthesis of wax esters from long-chain alcohols and fatty acids, and plays very important roles in plant wax synthesis and some resistances to drought, pathogenic bacteria, ultraviolet radiation, cold and insect invasion and other environmental stresses; cadmium (Cd) is one of the toxic heavy metals with the highest content in environment, and seriously threatens plant growth, development, quality, yield, and plant food safety. In order to explore the Cd stress expressions of wax ester synthase genes in Rehmannia glutinosa, we identified its wax ester synthase genes from its full-length transcriptome sequencing data, analyzed both physiochemical properties, phytogenetic trees and conserved domains with bioinformatics methods, and tissue expressions and Cd stress expressions using qRT-PCR. The results were as follows: (1) Two wax ester synthase genes, named as RgOATWSD1 and RgOATWSD2, were identified, whose coding proteins were unstable hydrophobic proteins with amino acid lengths of 463 aa and 473 aa, isoelectric points of 8.86 and 9.34 and molecular weights of 51.31 kD and 52.49 kD, respectively. (2) Both proteins contained a conserved acyl_WS_DGAT domain and DUF1298 superfamily, in which the former accounted for 92.65% to 94.50% of the amino acid sequence. (3) Both proteins were located in the endoplasmic reticulum and both secondary structures were mainly composed of random coil and α-helix;RgOATWSD2 was not transmembrane protein but RgOATWSD1. (4) Both were differentially expressed in the roots, stems and leaves of R. glutinosa plants. (5) Both expressions were highly responsive to Cd stress, but both expression change trends were different under Cd stress. This study identifies two wax ester synthase genes in response to Cd stress, and lays a foundation for further research on Cd stress expression and other functions of RgOATWSD.