Identification of candidate genes involved in wax deposition in Poa pratensis by RNA-seq

The cuticular wax plays important roles in plant resistance to various biotic and abiotic stresses. Understanding the synthesis and secretion of cuticular waxes is necessary in utilizing cuticular waxes to improve crop productivity and plant ecological adaptation. Due to the lack of genomic resources, little genetic research on cuticular wax deposition has been focused on Poa pratensis, a perennial forage and turf grass species that is widely distributed under various habitats. In this study, we performed de novo transcriptome sequencing to explore differentially expressed genes between the leaf non-elongation zone (NEZm) and the emerged blade zone (EBZ) and to identify genes related to cuticular wax deposition.

A total of 77,707,414 high quality reads were obtained from llumina HiSeq 2500 platform, which were then assembled into 106,766 unigenes. Among them, 6019 unigenes showed significant differences in expression between NEZm and EBZ. In our assembled sequences, 3087 SSRs molecular markers were discovered. All the unigenes were searched against the NR, Swissprot, GO, COG, and KEGG databases using BLAST program for functional annotation. From 3156 unigenes with more expression in NEZm compared to EBZ, a number of unigenes involved in very long chain fatty acids (VLCFAs) and cuticular wax biosynthesis, transportation and regulation were identified. Several unigenes related to defense response and epidermal patterning were also found. Twelve putative genes involved in VLCFAs and cuticular wax biosynthesis were further analyzed for their expressions using qRT-PCR.

The transcriptome of P. pratensis leaf was deep sequenced, de novo assembled and annotated, and the candidate genes potentially involved in VLCFAs and cuticular wax biosynthesis, secretion and regulation in P. pratensis were identified. This provides fundamental genetic resources in improving plant adaptation to abiotic and biotic stresses.