Cell Wall Metabolism And Related Genes During The Development Process Of Chinese Olive Fruit

Chinese olive [Canarium album(Lour.)Raeusch] fruit is rich in nutrients and unique in flavor.The fresh olive fruit has right qualities with tender flesh,crisp,sweet back,mastication and so on.It is very popular with consumers.Although there are many varieties of olives,most of the varieties can only be used for processing due to succulent of the fruit with rough and hard flesh,many fibers and bitter taste,etc.Therefore,In order to understand the reasons for the differences in the texture of Chinese olive fruit,the change of cell wall materials such as pectin,cellulose,and lignin and the activities of PME,Cx,POD and other related enzyme were study during the development of the fresh 'Qing Lan1' and the processed ' Chang Ying '.In the meanwhile,to explore the molecular mechanism of the differences in the texture of Chinese olive fruit,the differentially expressed genes related to pectin,cellulose and lignin of Chinese olive fruits were screened and cloned by combining with the transcriptome data of Chinese olive fruits,and the expression of the cloned gene during the development of Chinese olive fruit was determined by Real-time quantitative.The molecular mechanism of the difference in the texture of Chinese olive fruit is discussed in this paper,which provides a basis for further study on the formation of fruit texture differences during the development of olive fruit and the selection of the fresh Chinese olive varieties.The results were as follows:1.The change of cell wall materials content of cellulose,lignin and different forms of pectin were study during the development of the fresh'Qing Lan 1' and the processed ' Chang Ying '.The results show that the variation tendency of content of the WSP,CSP and cellulose were basically the same,but the content of the same period was different.The content of ISP,hemicellulose and lignin differed not only in the content,but also in the trend of change.Both cultivars maintained high content of cellulose during the whole fruit development.'Qing Lan 1' maintained higher ISP and lower CSP,hemicellulose and lignin content than 'ChangYing' after the 95 th day.Maintaining high cellulose content during the whole fruit development may be the main reason for maintaining high hardness of Chinese olive fruits.The difference of different forms of pectin,hemicellulose and lignin content may be the factors that form the difference of texture of two Chinese olive varieties.2.The changes of cell wall materials-related enzyme activities such as PME,Cx and PAL were determinated during the development of the fresh 'Qing Lan 1' and the processed ' Chang Ying '.The results show that the variation tendency of the PME,PG,Cx,PAL and POD activities were basically the same,but the activities were different in the fresh 'Qing Lan1' and the processed 'Chang Ying'.The PPO activity of 'Qing Lan 1' and'Chang Ying' was not noly different in activities,but also in different trends.Correlation analysis showed that the changes of WSP and ISP content were mainly related to PME activity,and the difference of CSP content might be related to PG activity;The correlation coefficient between Cx activity and cellulose content is small;PAL,PPO and POD activities are related to lignin content.The increase of PME activity might promote the degradation of pectin in Chinese olive fruits,causing the increase of ISP and WSP content;the change of Cx activity may have little effect on the change of cellulose content;the higher PAL and POD activities of the 'Qing Lan 1' than the 'Chang Ying' might be the reason why the early 'Qing Lan 1' lignin conten was higher than 'Chang Ying'.3.Three differentially expressed genes PL,PG and PGIP related to pectin,CESA1 and CESA2 related to cellulose,and six differentially expressed genes PAL,CCR1,CCR2,LAC1,LAC2 and POD related to lignin were found by combined with the changes of cell wall substances and the related enzymes in the fresh ‘Qing Lan 1' and the processed‘Chang Ying' and the transcriptome data of Chinese olive fruits.The ORF of these 11 genes was cloned by RT-PCR,and made analyses by bioinformatics.The result showed that the longest ORF was PAL gene with 2180 bp which encoded 726 amino acids,the shortest ORF was CESA1 gene with 848 bp which encoded 282 amino acids.The signal peptides predicted that PL,PG,PGIP,POD,LAC1 and LAC2 genes all have signal peptides,which belong to secreted proteins;The remainingPAL,CESA1,CESA2 and other genes do not have signal peptides and are not secreted proteins.the other genes do not have signal peptides which were not secreted proteins;The 11 genes cloned each contained 2 to 6transmembrane structures.The main components of the 11 gene structures was dominated by alpha helix and random coil,followed by?-turn.4.The expression levels of these 11 related genes in various stages of fruit development were determined by qRT-PCR,and correlation analysis was carried out.The results showed that the relative expressions of the seven genes include PL,PG,CESA1,CESA2,PAL,POD and LAC were similar in the period of 'Qing Lan 1' and 'Chang Ying',but there were differences in expression levels;The trend of relative expression levels and the expression levels of PGIP,CCR1,CCR2 and LAC2 genes were different in the two varieties and the expression levels were different in the period of 'Qing Lan 1' and 'Chang Ying'.Among the three genes related to pectin,the pectin content of two cultivars may be mainly regulated by PGIP gene;the CESA1 and CESA2 genes related to cellulose may mainly focus on the early stage of fruit development;among the six genes related to lignin,the changes of lignin content in early stage of fruit development may be mainly rugulated by PAL,CCR1,CCR2 and LAC1 genes.while POD gene may play a role in the late stage of fruit development.