Analysis of Delta(9) fatty acid desaturase gene family and their role in oleic acid accumulation in Carya cathayensis kernel

Xiaolin Si; Shiheng Lyu; Quaid Hussain; Hongyu Ye; Chunying Huang; Yan Li; Jianqin Huang; Jianjun Chen; Ketao Wang

doi:10.3389/fpls.2023.1193063

Analysis of Delta(9) fatty acid desaturase gene family and their role in oleic acid accumulation in Carya cathayensis kernel

Front Plant Sci. 2023 Sep 12:14:1193063. doi: 10.3389/fpls.2023.1193063. eCollection 2023.

Authors

Xiaolin Si¹, Shiheng Lyu¹, Quaid Hussain², Hongyu Ye¹, Chunying Huang¹, Yan Li¹, Jianqin Huang¹, Jianjun Chen³, Ketao Wang¹

Affiliations

¹ State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Lin'an, Zhejiang, China.
² College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, China.
³ Mid-Florida Research and Education Center, Environmental Horticulture Department, Institute of Food and Agricultural Sciences, University of Florida, Apopka, FL, United States.

Abstract

Carya cathayensis, commonly referred to as Chinese hickory, produces nuts that contain high-quality edible oils, particularly oleic acid (18:1). It is known that stearoyl-ACP desaturase (SAD) is the first key step converting stearic acid (C18:0, SA) to oleic acid (C18:1, OA) in the aminolevulinic acid (ALA) biosynthetic pathway and play an important role in OA accumulation. Thus far, there is little information about SAD gene family in C. cathayensis and the role of individual members in OA accumulation. This study searched the Chinese Hickory Genome Database and identified five members of SAD genes, designated as CcSADs, at the whole genome level through the comparison with the homologous genes from Arabidopsis. RNA-Seq analysis showed that CcSSI2-1, CcSSI2-2, and CcSAD6 were highly expressed in kernels. The expression pattern of CcSADs was significantly correlated with fatty acid accumulation during the kernel development. In addition, five full-length cDNAs encoding SADs were isolated from the developing kernel of C. cathayensis. CcSADs-green fluorescent protein (GFP) fusion construct was infiltrated into tobacco epidermal cells, and results indicated their chloroplast localization. The catalytic function of these CcSADs was further analyzed by heterologous expression in Saccharomyces cerevisiae, Nicotiana benthamiana, and walnut. Functional analysis demonstrated that all CcSADs had fatty acid desaturase activity to catalyze oleic acid biosynthesis. Some members of CcSADs also have strong substrate specificity for 16:0-ACP to synthesize palmitoleic acid (C16:1, PA). Our study documented SAD gene family in C. cathayensis and the role of CcSSI2-1, CcSSI2-2, and CcSAD6 in OA accumulation, which could be important for future improvement of OA content in this species via genetic manipulation.

Keywords: fatty acid composition; hickory; molecular docking; oleic acid; stearoyl-ACP-desaturase.

Grants and funding

This study was financially supported by a grant from “Pioneer” and “Leading Goose” R&D Program of Zhejiang (2022C02009), Zhejiang Province Key R&D Project (2021C02001), China Postdoctoral Science Foundation (2021M692867), the National Natural Science Foundation of China (No. 32101557, 32201596), the National Key R&D Program of China (2018YFD1000604), Zhejiang Agriculture New Variety Breeding Major Science and Technology Special (2021C02066-12), Research Development Foundation of Zhejiang A & F University (2034020151) and State Key Laboratory of Subtropical Silviculture (No. KF202001).