RNA-seq Analysis of Solanesol Biosynthesis Genes in Nicotiana tabacum

Solanesol is a noncyclic terpene alcohol composed of nine isoprene units and it mainly accumulates in solanaceous plants, especially tobacco (Nicotiana tabacum L.). Here, RNA-seq analyses of tobacco leaves, stems, and roots were used to identify solanesol biosynthesis genes. Six 1-deoxy-D-xylulose 5-phosphate synthase, two 1-deoxy-D-xylulose 5-phosphate reductoisomerase, two 2-C-methyl-D-erythritol 4-phosphate cytidylyltransferase, four 4-diphosphocytidyl-2-Cmethyl-D-erythritol kinase, two 2-C-methyl-D-erythritol 2,4-cyclodiphosphate synthase, four 1hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate synthase, two 1-hydroxy-2-methyl-2-(E)-butenyl 4diphosphate reductase, six isopentenyl diphosphate isomerase, and two solanesyl diphosphate synthase (SPS) genes were identified to be involved in solanesol biosynthesis. Furthermore, the two N. tabacum SPS (NtSPS1 and NtSPS2), which had two conserved aspartate-rich DDxxD domains, were highly homologous with SPS enzymes from other solanaceous plant species. In addition, the solanesol contents of three organs, and leaves from four growing stages, corresponded with the distribution of chlorophyll. Our findings provide a comprehensive evaluation of the correlation between the expression of different biosynthetic genes and the accumulation of solanesol in tobacco.