Dynamic Change Analysis Of Fruit Growth And Seed Oil Fatty Acid Content Of Camellia Vietnamensis

Camellia vietnamensis seed oil is an important forest product owing to its obvious regional characteristics and market competitive advantages and high economic value in Hainan Province.The high quality,yield and efficiency of C.oleifera are closely related to cultivation techniques and management measures.The fatty acids(FAs)composition of C.vietnamensis seed oil is an important factor affecting its nutritional and health values,but the theory of fruit growth and development,the mechanism of seed oil formation,the dynamic changes and molecular regulation mechanism of the FAs in this seed oil are still unclear.Four high-yielding adult seedling tree samples from 16-year-old Camellia plantation in Fushan Town,Chengmai County,Hainan Province were investigated to observe the dynamic changes of fruit growth.The Soxhlet method was used to extract oil,and the dynamic changes of oil rate in fruit,seed and kernel were analyzed.We used gas chromatography to determine the kinds and relative content of FAs,then analyzed the dynamic changes of different FAs and the linear correlation between them.The relative expression of four key enzyme genes was determined using real-time polymerase chain reaction for analyzing the relationship of that and FA content.The main results are displayed as follows:1.The indexes of fruit volume,fruit weight,peel weight,seed dry weight and fresh weight,kernel dry weight and fresh weight,water content and oil content of organs or tissues all showed the dynamic characteristics of S-shaped curve.2.From May to September was the rapid expansion period of fruits,and from May to August was the rapid expansion period of seeds.The preiod from August to October was the period of dry matter accumulation in seeds including oil.The water content of fruits showed an upward trend during the period from May to September,and that of seeds showed the same trend during the period from May to August.There were no significant changes in kernel dry weight and oil content of dry kernels after the first ten days of October.3.There were 15 kinds of FAs in the seed oil and that the proportions of palmitic acid,stearic acid,oleic acid,linoleic acid,linolenic acid,and tetracosenic acid all changed significantly in the course of their dynamic changes.Additionally,there was an extremely significant negative correlation between the contents of oleic acid and linoleic acid,similar to the correlation between those of saturated FAs and unsaturated FAs.Oleic acid accumulated rapidly from August 5th to September 5th,and this accumulation increased with the maturity of the seeds,while the accumulation of linoleic acid showed the opposite trend.4.Different FA contents changed in accordance with the relative expression of key enzyme genes controlling their transformation.The canonical correlation between the relative expression of key enzyme genes and the stearic acid(substrate),linolenic acid,and arachidonic acid(product)content was extremely significant.5.The relative expression of the SAD gene was significantly negatively correlated with the stearic acid content.The stearic acid content was significantly positively correlated with the relative expression of the FAD2 gene,as well as that of the SAD with FAD2 and FAD3 genes,similar to the correlation between linoleic acid content and the relative expression of FAD3 gene.It is evident that sufficient water should be supplied in the camellia forest from May to September,and fruit harvesting from early October will not affect the yield of camellia seed oil.There was a direct transformation from palmitic acid to stearic acid,from stearic acid to oleic acid,from oleic acid to linoleic acid,and from linoleic acid to linolenic acid.Choosing the right date for harvesting is one effective way to increase the proportion of unsaturated FAs in seed oil.The enhancement of SAD gene expression promoted the transformation from stearic acid to oleic acid.Stearic acid content has a positive effect on the expression of the FAD2 gene,similar to the effect of linoleic acid content on FAD3 gene expression,as well as that of the SAD gene on FAD2 and FAD3 genes expression.