Resin tapping transcriptome in adult slash pine (Pinus elliottii var. elliottii)

To better understand the bases of resin production, a major source of terpenes for industry, the transcriptome of adult Pinus elliottii var. elliottii (slash pine) trees under field commercial resinosis was obtained. Samples were collected from cambium after 5 and 15 days of treatment application, which included tapping followed by application of commercial resin stimulant paste or control wounding without paste. Overall mean number of reads of all 16 libraries (2 treatments x 2 times x 4 replicated trees) was 34,582,048. Of these, 89% were mapped against the reference sequence, with a mismatch of 0.58%. Using the Blast2Go, 570 candidate genes were detected based on sequence annotation. By comparing the expression profile between paste and control, 310 differentially expressed genes (DEGs) were identified at 5 days, and 190 at 15 days with a significant fold change of log(2) > 1.2. Regarding changes in time comparisons within each treatment, 210 and 105 DEGs were identified within control and paste treatment, respectively. Genes with different expression patterns in the times and treatments examined included ethylene responsive transcription factors, geranylgeranyl diphosphate synthase, diterpene synthase, cytochrome P450 and ABC transporters, all of which may play important roles in resin production. RT-qPCR analysis correlated well with the data obtained by RNAseq. Resin composition changed over time. This is the first transcriptomic investigation of resinosis of the main species used in the bioresin industry and of molecular analyses of resinosis under field operations, with implications for stand management, stimulant paste development, genotype selection and breeding for high resinosis.