Physiological And Biochemical Characteristics And Gene Expression Differences Of Lignin Metabolism In Pyrus Ussuriensis Maxim.

Pyrus ussuri ensis Maxim.occupies an important position in the production of fruit trees in cold regions of China.It has the characteristics of rich fruit aroma and strong cold resistance.However,due to the degeneration of varieties in recent years,the occurrence of severe calyx,the increase of persistent calyx pear,and the increase of stone cells have seriously affected the quality of fruits and reduced their market competitiveness.In this study,Pyrus ussuriensis Maxim.was used as the main test material to study the lignin in fru its from different aspects to understand the changes of intermediate metabolites and gene expression patterns of lignin synthesis,which laid the foundation for effective regulation of Pyrus ussuriensis Maxim.stone cells.The main contents are as follows:During the development of fruit,the fruit weight,transverse diameter and vertival diameter of Jianba pear were higher than that of Nanguo pear.the lignin content of Jianba pear was always higher than that of Nanguo pear.In the early stage of development,both lignin contents were high.With the growth and development of fruits,their lignin content gradually decreased.130 days after full bloom,the lignin content of Nanguo pear was only 19.3% of the Jianba pear.The area of vertival section dyeing of fruit was mainly concentrated around the nucleus,and the degree of dyeing was consistent with the change of lignin content.Analys is of fruit phenolic compounds found that the content of lignin intermediates in Nanguo pear fruit was lower than that of Jianba pear,and the total amount of flavonoids was higher than that of Jianba pear,which was significantly related to the accumulation of lignin.The lignin synthesis gene expression of the two varieties has temporal and spatial specificity.Overall,LAC,C3 H and PAL genes are highly related to the lignin content in the two varieties,and may be the key genes that cause differences in their lignin accumulation.With the development of fruit,the fruit growth of dropping calyx pear and persistent calyx pear was similar.The fruit lignin content in dropping calyx pear was always lower than that in the persistent calyx pear.130 days after full bloom,the fruit lignin content of dropping calyx pear and persistent calyx pear was 1.6% and 3.8%,respectively.From the dynamic analysis results of the content of phenolic components,the content of lignin intermediate product in the dropping calyx pear was lower than that of the persistent calyx pear,the content of flavonoids was higher than that of the persistent calyx pear and was signif icantly related to the accumulation of lignin.Analysis of genes related to lignin synthesis pathways revealed that C3 H and 4CL genes may be the key genes affecting the differences in lignin synthesis between dropping calyx pear and persistent calyx pear.In the process of Nanguo pear fruit development,the stone cell content was consistent with the change trend of lignin content,and the fruit had a higher content in the early stage of fruit development and gradually decreased in the later per iod.The fruit lignin and ROS were histochemically localized,and the ROS level and the fruit lignin content were synchronized in time and space.The study found that there is a close relationship between the levels of NADP H oxidas e,SOD and POD activities and the content of stone cells in ROS and ROS metabolism related enzymes.In the study,the POD,SOD and NOX activities in fruits were consistent with changes in lignin content in fruits.During the early per iod of fruit development,their activities were relatively high.With the development of fruits,their activity was gradually reduced and maintained at a stable level.By analyzing the expression level of RBOH gene,there was a correlation between RBOH gene and fruit lignin content.This experiment studied the physiological and biochemical characteristics and gene expression differences of lignin metabolism in Pyrus ussuriensis Maxim.fruit from different angles,and provided an important theoretical basis for how to regulate the stone cells of Pyrus ussuriensis Maxim.fruit.