Transcriptome Analysis of Avocado Mesocarp Reveals Key Genes Necessary to Improve Oil Yield

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Avocado is an economically important crop with ~70% oil in its fruit tissue, which is an essential component of human diet. The steady increase in global demand for avocado production (9%/year) has drawn attention to the importance of understanding the genetic regulation of triacylglycerol (TAG) accumulation. Using RNA-seq approach, mesocarp-specific regulation and biosynthesis of TAG in developing avocado fruit was analyzed. During the period of TAG accumulation in the mesocarp, an increased expression was noted for genes mostly associated with hexose metabolism in plastids, including pyruvate kinase, relative to cytosol, which is likely associated with the need for higher pyruvate flux directed toward plastid fatty acid synthesis. A corresponding increase in expression for plastidial fatty acid synthesis genes was also noted but not for TAG assembly genes. Additionally, WRINKLED1 (WRI1), a regulatory element typically associated with seed oil biosynthesis, was also highly expressed in oil-rich mesocarp of avocado, along with two other isoforms of WRI. Transcriptomics also revealed that multiple acyltransferases that participate in rate-limiting step in TAG synthesis might be active concomitantly in mesocarp to achieve higher levels of TAG accumulation. Similar observations were previously made with transcriptome analysis of oil-rich seed and non-seed tissues. Together these data suggest a ubiquitous role for WRI1 and that a major point of regulation of oil biosynthesis in oilrich mesocarp tissue most likely occurs at the level of source and not sink. Overall, this study provides a foundation for functional genomics required to direct metabolic engineering efforts to enhance avocado oil yield.


Champaign, IL

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