Characterization of <i>CiWRI1</i> from <i>Carya illinoinensis</i> in Seed Oil Biosynthesis

Abstract

Pecan (Carya illinoinensis) is a widely consumed edible woody oil species that is rich in unsaturated fatty acids (FAs) that are beneficial to human health. However, the genes and mechanisms regulating seed oil biosynthesis in pecan are not well understood. Here, we analyzed the expression patterns of genes involved in seed oil biosynthesis in two different varieties of pecan with distinct fruit maturation schedules and oil contents. We cloned the C. illinoinensis WRINKLED 1 (CiWRI1) gene, a homolog of ArabidopsisWRINKLED1 (AtWRI1), which plays a key role in FA synthesis. Overexpressing CiWRI1 restored lipid synthesis in the Arabidopsiswri1-1 mutant and rescued other phenotypic defects such as plant height, root length, and germination rate, suggesting that CiWRI1 is an ortholog of the AtWRI1 and is involved in the regulation of FA synthesis. To investigate the mechanism of CiWRI1 regulation, we cloned C. illinoinensis BIOTIN CARBOXYL CARRIER PROTEIN ISOFORM2 (CiBCCP2) and determined that the CiWRI1 protein directly binds to an ASML1/WRI1 (AW)-box motif in the CiBCCP2 gene promoter and thereby activates its transcription. CiBCCP2 overexpression partly rescued the phenotypic defects of the wri1-1 mutant, indicating that it is directly regulated by CiWRI1. Thus, de novo FA biosynthesis in seed is conserved across plant species; moreover, CiWRI1 regulates oil synthesis by directly controlling CiBCCP2 expression. These findings present novel potential targets for molecular-marker-assisted breeding of this commercially important plant.

Keywords

• pecan oil content
• fatty acid synthesis
• <i>CiWRI1</i>
• <i>CiBCCP2</i>