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

, 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 gene family in and the role of individual members in OA accumulation. This study searched the Chinese Hickory Genome Database and identified five members of genes, designated as , at the whole genome level through the comparison with the homologous genes from . RNA-Seq analysis showed that , and were highly expressed in kernels. The expression pattern of was significantly correlated with fatty acid accumulation during the kernel development. In addition, five full-length cDNAs encoding were isolated from the developing kernel of . CcSADs-green fluorescent protein (GFP) fusion construct was infiltrated into tobacco epidermal cells, and results indicated their chloroplast localization. The catalytic function of these was further analyzed by heterologous expression in , , and walnut. Functional analysis demonstrated that all had fatty acid desaturase activity to catalyze oleic acid biosynthesis. Some members of also have strong substrate specificity for 16:0-ACP to synthesize palmitoleic acid (C16:1, PA). Our study documented gene family in and the role of , and in OA accumulation, which could be important for future improvement of OA content in this species via genetic manipulation.