The Regulating Mechanism Of PbNAC83a,PbNAC83f And PbNAC91a About Lignin Synthesis On Pear Fruits

According to the distribution of pear stone cell in pear pulp,the pear pulp was divided into the dearth area(middle part of pupl)and the abundant area(pupl near kernel).Studying the effects of light quality on stone cell synthesis and lignin metabolism in these two parts,we determined the stone cell and lignin content in the’Dangshansuli’ pear fruit using different color transparent fruit bags.The difference of the stone cell and lignin content between ’Dangshansuli’ and ’Cuiguan’ was compared.On the basis of field experiments,the temporal and spatial expression analysis of the effects of light quality on PbNAC83a,PbNAC83f and PbNAC91a was carried out,and the analysis of gene function and molecular regulation mechanism was carried out.The results are as follows:1.There were differences in pear fruit of distribution of stone cell and lignin between the middle plup and plup near kernel.The content of stone cell and lignin in the middle part of the pulp was significantly lower than that in the pulp near kernel.The orange transparent bag has the lowest blue/UV ratio,and the red/blue ratio is the highest.The green transparent bag has the highest blue/UV ratio,and the red/blue ratio is lower than the orange transparent bag than the colorless transparent fruit bag.After treatment with different color transparent bags,the orange transparent bag can significantly promote the accumulation of stone cell and lignin in the fruit.The green transparent bag can promote the accumulation of stone cell and lignin in the middle of the pulp,inhibiting accumulation of stone cell and lignin at the plup near kernel.The peak of stone cell content of‘Cuiguan’during whole growth period is 40-45 days after full blossom,and the fruit growth period is about 130 days;the peak of stone cell content of ’Dangshansuli’ during whole growth period is 50-55 days after full blossom,and the fruit growth period is about 150 days.The stone cell content of ’Cuiguan’ is significantly lower than that of ’Dangshansuli’,but the lignin content of dried flesh does not have much difference,indicating that the lignin content in the dried flesh does not depend on the content in stone cell.2.PbNAC83a,PbNAC83f and PbNAC91a were found highly expressed at stone cell accumulating rapidly phase by q-PCR.PbNAC83a and PbNAC83f were more active in the middle part of the plup,and PbNAC91a was more active in the middle part of the plup in the early stage of accumulating rapidly phase of stone cell,and more active in the plup near kernel during the late stage of accumulating rapidly phase of stone cell.The expression of three NAC translation factors has changed by using green and orange transparent bags.After using different color transparent bags,the orange transparent bag promotes the expression of PbNAC83a in different parts of the pulp,the green transparent bag inhibits the expression of PbNAC83a,the green and orange transparent bags all promote the expression of PbNAC83f,and orange transparent bag promotes the expression of PbNAC91a.Green transparent bag only promotes the expression of PbNA C91a in the plup near kernel.3.PbNAC83a,PbNAC83f and PbNAC91a are localized on the nucleus.Overexpression of PbNAC83a transient transformation to ’Dangshansuli’ leaves and pear fruits can cause a significant increase of lignin content,transiently transformed tobacco leaves increased lignin content but did not reach a significant level,and inhibition of PbNAC83a gene transient transformation into tobacco leaves cause a significant decrease of lignin content.Overexpression of PbNAC83f transiently transformed into ’Dangshansuli’leaves and tobacco leaves can cause a significant increase of lignin content,and inhibition of PbNAC83f gene transient transformation to tobacco leaves caused a significantly decrease of lignin content.Corresponding changes have also taken place in expression of lignin-ralative genes.Dual luciferase assay demonstrated that recombinant PbNAC83a and PbNAC83f significantly induced transactivation of the promoter of PbPOD2 proteins.Overexpression of PbNAC91a transiently transformed into ’Dangshansuli’ leaves and pear fruits caused a significant increase of lignin content,and inhibition of PbNAC91a gene transient transformation to tobacco leaves caused a significantly decrease of lignin content.Corresponding changes have also taken place in expression of lignin-ralative genes.