Transcriptome and gene expression analysis revealed mechanisms for producing high oleoresin yields from Simao pine (Pinus kesiya var. langbianensis)

Simao pine (Pinus kesiya Royle ex Gordon var. langbianensis (A. Chev.) Gaussen) is an important oleoresin source in Yunnan Province, China. However, the molecular mechanisms of high oleoresin yield from Simao pine remain unclear. In this study, RNA-Seq was used to investigate the transcriptome of the species and compare the gene expression profiles of wounded bark from high and low oleoresin-yielding individuals, and the expression levels of genes in the methyl-erythritol 4-phosphate (MEP) pathway were detected by qPCR. A total of 1.41 billion reads were obtained and assembled into 68,881 unigenes from samples of the wounded bark of Simao pine. The KEGG analysis of differentially expressed genes showed that MEP pathway genes were obviously differentially expressed, while most genes in the mevalonate (MVA) pathway were not. The qPCR analysis showed that the MEP pathway gene expression of wounded bark from high oleoresin-yielding genotypes was higher than that of low oleoresin-yielding genotypes. The gene expression differences of 1-deoxy-D-xylulose-5-phosphate synthase (DXS), 4-hydroxy-3-methylbut-2-enyl diphosphate reductase (HDR), and geranylgeranyl pyrophosphate synthase (GGPPs) between high and low oleoresin-yielding genotypes were significant. This implies that DXS, HDR, and GGPPs play important roles in high oleoresin production in Simao pine.