Effect of bagging on expression of crucial structural genes of anthocyan⁃in biosynthesis in‘Tianyuanhong’kiwifruit based on RNA-seq

 Abstract:【Objective】The aim of this survey is to explore the effect of bagging on expression of crucialstructural genes of anthocyanin biosynthesis of different parts of kiwifruit fruits in different stages ofgrowth and development and provide evidence for the impacts of illumination on anthocyanin synthesis.【Methods】Full red-flesh fruits of kiwifruit‘Tianyuanhong’were selected as materials for bagging treat⁃ments. According to the RNA-seq, 12 differential expression genes (DEGs) were screened. These 12 se⁃lected DEGs were conducted to analysis on the expression rule in the seven stages using quantitative realtimepolymerase chain reaction (qRT-PCR). Finally, the crucial candidate genes were confirmed basedthe results of qRT-PCR and cluster analysis. And then the relative quantitative analysis of expression level of the crucial candidate genes in different treatments, different periods and different parts of fruits wasconducted by the qRT-PCR, and furthermore, the correlation analysis between expressions of genes andanthocyanin contents was also conducted.【Results】The expressions of 12 structural genes presented regu⁃lar change rules although their expressions were different. The expression levels of F3H, LDOX and F3GT110 days after full bloom (DAFB) when the flesh turned to be red were higher than those in other stages.The results of cluster analysis showed that LDOX and F3GT were respectively clustered into one class andwere obviously separated from other genes. The expression level of LDOX of epicarp of treatment 1 dis⁃played an increase trend and reached peak on 110 d during the growth and development of fruits. Whilethe levels of LDOX of epicarp of treatment 2 and treatment 3 were lower than that of treatment 1, especial⁃ly on 100 d and 110 d. This indicated that bagging treatment and bagging-debagging treatment could de⁃crease the expression level of LDOX in epicarp when the flesh turned to be red. The changing rule ofLDOX expression level of sarcocarp of treatment 1 was similar to the trend of epicarp. As the developingof fruit, the expression level of LDOX increased and reached its maximum value on 110 d and it was evi⁃dently higher than those in other stages. While the expression level of expression LDOX of treatment 2 andtreatment 3 was obviously lower than that of treatment 1. This phenomenon suggested that bagging treat⁃ment and bagging-debagging treatment could decrease the expression level of LDOX in sarcocarp. Therewas no obvious changing rule for the expression of LDOX of columella of treatment 1 and treatment 2.However, the expression level of LDOX of treatment 3 was higher than that of treatment 1 and treatment 2on 110 d, which hinted that bagging treatment promoted the expression of LDOX in columella. The expres⁃sion level of F3GT in epicarp of treatment 1, treatment 2 and treatment 3 displayed a similar changingrule during the period of growth and development of fruit. The expression level of F3GT increased from 90d to 110 d, but the expression level of F3GT of treatment 1 was higher than that of treatment 2 and treat⁃ment 3, especially on 110 d. And the expression level of F3GT of treatment 2 was higher than that of treatment 3. These phenomenon indicated that bagging-debagging treatment could increase the level of F3GTin epicarp. The expression level of F3GT in sarcocarp of treatment 1 displayed an increase trend andreached peak on 100 d, which was the same as the expression level of LDOX in sarsocarp. The expressingof F3GT in columella of treatment 1, treatment 2 and treatment 3 had no obvious rule. The expression lev⁃el of LDOX in sarcocarp of treatment 1 and treatment 2 and the expression level of LDOX in columella oftreatment 3 had a very significant correlation with anthocyanin content. And the correlation between ex⁃pression level of LDOX in epicarp and sarcocarp of treatment 3 and anthocyanin content was statisticallysignificant. The expression level of F3GT in sarcocarp of treatment 1 and the expression level of LDOX incolumella of treatment 3 had a very significant correlation with anthocyanin content. And the correlationbetween expression level of LDOX in epicarp of treatment 3 and the expression level of LDOX in sarco⁃carp of treatment 2 and anthocyanin content were also statistically significant.【Conclusion】LDOX andF3GT might be the crucial structural genes of anthocyanin biosynthesis in the fruits of‘Tianyuanhong’ki⁃wifruit. Bagging treatment inhabited the expression of LDOX in epicarp and sarcocarp, while it promotedthe expression of LDOX in columella. Bagging-debagging treatment promoted the expression of F3GT inepicarp while it suppressed the expression of F3GT in sarsocarp, which was consistent with the expressionrule of LDOX in sarcocarp. Bagging treatment had no obvious impact on expression of F3GT in columella.