Study On Leaf Color Change Process And Molecular Mechanism Of Young Leaves Of Podocarpus Costalis

The young leaves of Podocarpus costalis are brightly colored,usually red,pink,etc.This is a rare colorful leaf phenomenon among many Podocarpus plants.In order to explore the leaf color change process and molecular mechanism of the young leaves of P.costalis,this study used the young leaves of P.costalis at different growth stages as materials,freehand sectioning to observe pigmented parts,measured the phenotype and content of various pigments,analyzed the transcriptome by RNA-Seq,selected the appropriate reference genes by q RT-PCR,explored the expression patterns of genes related to anthocyanin and chlorophyll synthesis,analyzed the correlation between pigments and genes,laying a foundation for mining the functions of anthocyanin synthesis pathway related genes.The main results are as follows:(1)The veins and epidermal cells of the young leaves of P.costalis are green,and some mesophyll cells are red.The L* value decreased firstly and then increased,the a* value increased first and then decreased,the b* value increased continuously,and the C* value increased first,then decreased and finally increased.The contents of chlorophyll a,chlorophyll b and total chlorophyll were obviously increased.The content of carotenoid was less and total flavonoids was more,but the change trend of both was not obvious.(2)Four anthocyanins were detected in the young leaves of P.costalis: delphinidin 3-O-glucoside,cyanidin 3-O-glucoside,petunidin 3-O-glucoside,cyanidin 3-O-rutinoside.The contents of the four anthocyanins showed the same trend,which reached the highest and then decreased.Among them,cyanidin 3-O-glucoside had the highest content and was red,which was consistent with the change trend of leaf color phenotype a* value.It was speculated that cyanidin 3-O-glucoside was the main color substance of in the young leaves of P.costalis.(3)A total of 52 189 Unigene were obtained by transcriptome sequencing.By comparing the expression levels of genes in young leaf at different stages,1 376 differentially expressed genes were found.Among them,33 differentially expressed genes were involved in anthocyanin biosynthesis pathway and 13 differentially expressed genes were involved in porphyrin and chlorophyll metabolism pathway.(4)When the expression levels of 12 candidate reference genes were analyzed,the results showed that UBCE and e IF were the most stable reference genes,while UGP3 was less stable.(5)Among the genes related to anthocyanin biosynthesis,the expression levels of CHS,CHI,F3’5’H,DFR,ANS and MT showed a trend of first increasing and then decreasing,which was consistent with the accumulation of anthocyanins content.Among the genes related to chlorophyll biosynthesis,the expression levels of HEMA,CHLI,CHLD,DVR and PROA showed an upward trend,which was consistent with the change trend of chlorophyll a,chlorophyll b and total chlorophyll.It is speculated that the redness of the young leaves was caused by the increase of the expression of genes related to anthocyanin biosynthesis,and the red to green of the young leaves was caused by the decrease of anthocyanin biosynthesis related gene expression and the increase of chlorophyll biosynthesis related gene expression.