Effect Of Pollination On Secondary Cell Wall Lignin Biosynthesis In'Guanximiyou' (citrus Grandis) Central Juice Sacs

In this study,the physiological indexes of 'Guanximiyou'(citrus grandis)cross-pollinated fruit and central juice sacs on Aug.20th,Sep.20th,Oct.20th(harvest period)and Nov.20th(storage 1 Months)were measured in comparison with self-pollinated fruit.lignin was observated and the expression of related genes in lignin biosynthesis was analyzed by fluorescence quantitative PCR.The main results are as follows:1.There were only abortive seeds in a fruit of 'Guanximiyou,(citrus grandis)by self-pollination,and were above average 63 grains by cross-pollination,indicating that the seedlessness was caused by self-incompatibility.2.With the pomelo fruit ripening,granulation index,lignin and cellulose content in self-and cross-pollinated fruit was rising,and could be reduced by cross-pollination.The contents of total soluble solids,titratable acids and VC in fruit juice sacs were decreased in different degrees,and could be improved by cross-pollination.This paper also found that the granulation index was negatively correlated with VC content,and was positively correlated with the content of cellulose and lignin.The ratio of tss to ta was negatively correlated with lignin.The content of VC was negatively correlated with the content of cellulose and lignin.There was a positive correlation between cellulose and lignin.3.By microscopic observation,the lignin of secondary cell wall in juice sacs did not be detected in the fruit ripe early period,and were observed in self-pollinated fruit juice sacs in September,The accumulation of lignin was found at the harvest date,and became more severe during the storage period,and there were more dense lignin distribution at the upper of the fruit juice sacs than at the lower.Cross-pollination could delay the occurrence of granulation and reduce the degree of granulation.4.The expression of 16 related genes in lignin biosynthesis pathway was analyzed.? The PAL and C4H participating in the initial lignin biosynthesis were gradually increased with the fruit ripening,and were positively correlated with the changes of lignin biosynthesis.The cross-pollination could significantly reduce the expression of PAL gene in fruit juice sacs.? There were positive correlation between the expression of C3H and HCT participating in Hydroxy reaction and lignin,while F5H gene was inconsistent in self-and cross-pollinated fruit juice sacs.? The expression of CCoAOMT and CCoAOMT2 in methyl reaction were slowly rising in keeping with lignin content.Only 4CL expression was more in line with lignin biosynthesis,and 4CL2 might not be involving in lignin biosynthesis;? The expression of CCR involved in the reduction reaction was a positive correlation with the content of lignin.While the CCR2 gene was a little expression in the later periods of fruit ripening,there was a negative correlation between the CAD gene and the lignin content in self-and cross-pollinated fruit juice sacs,which might not be involved in the biosynthesis of lignin;? The expression of POD increased with fruit ripening,and was a significant positive correlation with the changes of lignin content.The expression of BRT1 gene in self-pollinated fruit juice sacs is high,while almost no expression in cross-pollinated fruit juice sacs.Therefore,it was speculated that the lignin biosynthesis of pomelo juice sacs was in favor of G-lignin synthesis.