Functional Validation of Wrinkled Orthologs in Avocado Oil Biosynthesis

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Triacylglycerol (TAG) is a class of lipid molecules composed of three fatty acyl chains esterified to a glycerol backbone. In plants, TAG is synthesized in various tissues and serves as a carbon and energy source. Oil biosynthesis is well understood in oilseeds however how plants store oil in non-seed tissue is yet to be determined. In Avocado (Persea americana), a basal angiosperm, TAG is exclusively accumulated in mesocarp tissue and therefore is emerging as a model system to uncover underlying mechanisms of TAG biosynthesis in tissues other than seed. The mesocarp of Avocado fruit contains ~60-70% of oil by dry weight. Recent transcriptome studies revealed that the TAG biosynthesis is transcriptionally regulated in non-seed tissues. In seed tissues, TAG biosynthesis is regulated by many seed maturation factors directly or indirectly through downstream transcription factor WRINKLED1 (WRI1). Transcriptome studies revealed that in addition to ortholog of WRI1, orthologs for WRI2 and WRI3 were also highly expressed in avocado mesocarp during the period of oil accumulation. Currently, cloning of Putative PaWRI 1, 2 and 3 genes into a binary vector, followed by agrobacterium-mediated transformation to generate transient and stable transient lines, is underway. Transient expression of putative PaWRI 1, 2 and 3 genes, using tobacco leaf assay, are expected to enhance oil accumulation in leaf tissues. Stable expression of PaWRI 1, 2, and 3 in Atwri-/- is expected to restore oil accumulation in seeds. TAG content and composition will be determined by gas chromatography coupled with flame ionization detector. Functional validation of these orthologs is expected to reveal the preferred WRI isoform that likely participates in regulation of oil biosynthesis in avocado mesocarp. Additionally, this work may also elucidate the differences between regulation of TAG accumulation in seed and non-seed tissues and identify new targets to enhance TAG biosynthesis in plants.


Johnson City, TN

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