Comparative transcriptomic analysis reveals genes related to the rapid accumulation of oleic acid in Camellia chekiangoleosa, an oil tea plant with early maturity and large fruit.

Camellia chekiangoleosa has a higher oleic acid content and a shorter reproductive cycle than typical oil tea plants. It was intensively sampled over six C. chekiangoleosa seed development stages. The content of fatty acids determined by GC showed that the accumulation of fatty acids gradually increased from the S1 to S5 stages, and the maximum concentration was reached in S5. Then, fatty acids declined slightly in S6. The main fatty acid component showed the same accumulation trend as the total fatty acids, except linolenic acid, which remained at a low level throughout seed developmental stages. Changes in the expression of fatty acid accumulation-related genes were monitored using second-generation and SMRT full-length transcriptome sequencing. Finally, 18.92 G accurate and reliable data were obtained. Differential expression analysis and weighted coexpression analysis revealed two "gene modules" significantly associated with oleic acid and linoleic acid contents, and the high expression of ENR, KAS I, and KAS II, which accumulate substrates for oleic acid synthesis, was thought to be responsible for the rapid accumulation of fatty acids in the early stage. The rapid increase in fatty acids in the second stage may be closely related to the synergy between the high expression of SAD and low expression of FAD2. In addition, many transcription factors, such as ERF, GRAS, GRF, MADS, MYB and WRKY, may be involved in the fatty acid synthesis. Our data provide a rich resource for further studies on the regulation of fatty acid synthesis in C. chekiangoleosa.