Camellia oil trait and DIA quantitative proteomics analyses reveal the impact of harvesting time on the oil content and quality of the late-maturing cultivar C. oleifera ‘Huaxin’

Harvesting fruits prematurely is a serious problem in many Camellia oleifera ‘Huaxin’ orchards. Systematic views of dynamic alterations in central metabolism associated with the oil content and oil quality of this cultivar at different harvesting dates were investigated. Oil trait analysis was performed in conjunction with data-independent acquisition proteomics analysis using kernels harvested at three time points. Samples were taken from different years and locations to verify oil trait changes, and parallel reaction monitoring (PRM) was performed for some pivotal proteins to validate changes in their abundance. Samples harvested at 6 days after the recommended harvesting date had the highest contents and best fatty acid composition of Camellia oil. A total of 614 differentially accumulated proteins were detected in three pairwise comparisons. Six days prior to the recommended harvesting date, maximum expression of ribonucloprotein, helicase ATP-binding domain-containing protein, and glycerol kinase and the highest seed moisture content were observed. Highest mitogen-activated protein kinase 6, very-long-chain 3-oxoacyl-CoA reductase and stearoyl-CoA desaturase expression appeared on the recommended harvesting date. A delayed effect was observed for proteomic and oil trait data. Oil trait and PRM validations indicated our results to be highly reliable. The current data strongly suggest that in Guizhou Province,’Huaxin’ cannot be harvested earlier than the recommended harvesting date; appropriately delaying the harvesting time can improve the ultimate production and quality of Camellia oil.