Overexpression of Heteromeric GhACCase Subunits Enhanced Oil Accumulation in Upland Cotton

Acetyl-CoA carboxylase (ACCase) catalyzes acetyl-CoA to produce malonyl-CoA, which is the essential first step in the biosynthesis of de novo fatty acids. The heteromeric ACCase of higher plants, such as upland cotton, is composed of four subunits: biotin carboxyl carrier protein (BCCP), biotin carboxylase (BC), α-subunit of carboxyltransferase (CTα), and β-subunit of carboxyltransferase (CTβ). In this study, four subunits encoding heteromeric ACCase were amplified and the structures were analyzed further. The result showed that 7, 16, 10, and 1 exon(s) were identified from GhBCCP1, GhBC1, GhCTα2, and GhCTβ, respectively. The expression pattern analysis showed that the transcripts of these four subunits were ubiquitous in all the tested tissues and may have a positive correlation between the four subunits and oil accumulation. The four subunits coordinate to enhance oil content. The expression patterns and levels varied under ABA, MeJA treatments, and cold stress. Furthermore, under the control of a seed-specific AGP promoter, overexpression of the four subunits separately in Upland cotton demonstrated that GhBCCP1 transgenic plants showed a significant increase of 21.92% in oil content in cotton seeds, while about a 17% increase was noted for GhBC1 and GhCTβ, respectively. So overexpression of each subunit of heteromeric GhACCase may effectively increase seed oil content in Upland cotton.