Comparative Transcriptomics Identifies Key Steps in Storage Oil Biosynthesis in Plant Tissues

Triacylglycerols (TAGs) are stored in variable amounts in diverse tissues of several plant species. Using comparative transcriptomics approach, we analyzed tissue- and species-specific regulation and biosynthesis of TAG in plants. In both seed and nonseed oil-rich tissues, irrespective of the species, an increased expression was noted for genes mostly associated with plastidial fatty acid synthesis but not TAG assembly in the endoplasmic reticulum. Furthermore, the transcripts associated with hexose metabolism in plastids of oil-rich tissues also showed higher expression, relative to cytosol, which is likely associated with the need for higher pyruvate flux directed toward plastid fatty acid synthesis. Together, these data suggest that a major point of regulation of oil biosynthesis in oil-rich tissues most likely occurs at the level of source and not sink. Additionally, WRINKLED1 transcription factor, a regulatory element typically associated with seed oil biosynthesis, was also highly expressed in oil-rich nonseed tissues of oil palm, a monocot and avocado, a basal angiosperm. Additional transcriptional regulators that are likely associated with TAG synthesis, exclusively in nonseed tissues were also identified. Overall, a comparative transcriptome analysis in diverse plants and tissues revealed several distinct and conserved features for storage oil biosynthesis and provided information needed to control carbon partitioning and increase oil accumulation for bioenergy in nonseed perennial crops.