| As a coproduct of tea production,annual output of tea fruit is as high as 10 t.Most of fruit has been wasted except a small amount for planting.The main components of tea seeds are fat,crude fiber,tea saponin and the kernel contains 24% ～ 25% oil.The composition of fatty acids is mainly MUFAs.So tea seed oil has high nutritional value.In this study,transcriptome sequencing,q RT-PCR and Gas Chromatography were used to explore the molecular mechanism of oil metabolism and relative content of fatty acids in young,formation and mature stage of seed in ’Tieguanyin’ cultivar.The results showed the variation tendency of gene expression and the relative content of fatty acids.It layed a foundation for the study of tea seed development regulation and also provided a theoretical reference for the breeding of newtea varieties.The main results of this study are as follows:1.Transcriptome analysis of tea seed in development stagesTranscriptome analysis showed that a total of 36951 Unigenes were obtained.The q PCR primers were designed,and the accuracy of transcriptome was verified.Combined with GO and KEGG analysis,35 DEGs in 9 pathways were selected as candidate genes.Physicochemical properties prediction results indicated that most genes were found to have the highest homology with oil tea.2.Fatty acid content changes during tea seed ripening stageThe relative contents of major fatty acids in the ripening process(Jul.29,Aug.12,Aug.26,Sep.9,Sep.23,Oct.7,Oct.21,Oct.28,Nov.4,Nov.11,Nov.18 and Nov.25)of ‘tieguanyin’ seeds were analyzed.The results showed that the five major fatty acids in oil accounted for 96.84%-98.20% of all fatty acids,and USFAs are the main components,accounting for 70.51%～75.14%.During the ripening stage of tea seeds,the relative content of palmitic acid(C16:0)decreased from 24.9% to 16.2%,the relative content of stearic acid(C18:0)increased from 1.43% to 2.86%,the relative content of oleic acid(C18:1)increased from 21.0% to 50.6%,the relative content of linoleic acid(C18:2)decreased from 46.4% to 28.1%,the relative content of α-linolenic acid(C18:3)decreased from 3.11% to 0.44%.Finally the relative contents of main fatty acids in tea seeds began to stabilize around November 18.3.Expression analysis of 35 genes related to fatty acid metabolism during tea seed development Stage I(young stage): During fatty acid synthesis,the expression of Cs ER2 in FAS was the highest.The synthesis of SFA was mainly affected by Cs HD,Cs MCAT,Cs ER2 and Cs FATB1.In the process of fatty acid desaturation,the expression of Cs SAD6 and Cs FAD3 reached a high level.The synthesis of USFA might mainly affected by Cs SAD6 and Cs FAD3.Stage Ⅱ(formation stage): During fatty acid synthesis,the expression levels of Cs HD and Cs ER2 were still high,and the expression level of Cs ACAT increased to 5.26 times in comparison with stage I.The synthesis of SFA was mainly affected by Cs ACAT、Cs HD and Cs ER2.In the process of fatty acid desaturation,the expression level of Cs SAD3 gene increased to 2.0 times in comparison with stage I,and the expression level also was the highest among desaturated enzyme genes.The synthesis of USFA might mainly affected by Cs SAD3.Stage Ⅲ(mature stage): During fatty acid synthesis,the expression of Cs ACAT reached the highest level and also was 5.9 times in comparison with stage I.The synthesis of SFA was mainly affected by Cs ACAT.In the process of fatty acid desaturation,the expression of SAD family all increased to a high level,and Cs SAD3 was 2.3 times in comparison with stage I.The expression of Cs FAD2 increased to the highest level,which was 2.1 time in comparison with stage I.The synthesis of linoleic acid was mainly affected by Cs FAD2.Mature stageis the main period for fatty acid desaturation and the main period for oleic acid content to rise. |
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