Effects Of Phenylalanine On Tyrosine Pathway-deficient Mutant Sscd1 In Arabidopsis Thaliana

Tyrosine degradation pathway played an essential role in animal metabolism.The interruption or blockage of this pathway would led to metabolic disorders and even individual deaths.In animals,phenylalanine could be converted to tyrosine and then metabolized by the tyrosine degradation pathway,but it was not clear in plants.To explore whether phenylalanine in plants also be metabolized by the tyrosine degradation pathway,the effects of phenylalanine on seed germination,seedling growth,gene expression of tyrosine degradation pathway and anthocyanin accumulation in Arabidopsis thaliana wild type and tyrosine degradation pathway-deficient mutant sscd1 were studied.The results showed that:1.Certain amount of phenylalanine inhibited seed germination,and the inhibitory effect on sscd1 mutant was higher than that of the wild type.2.The treatments of phenylalanine inhibited the root length of seedlings.However,the growth of aboveground parts of seedlings were promoted at low concentrations(0.1,0.5mmol·L^-1)and inhibited at high concentrations(1,2 mmol·L^-1),the inhibition effect on sscd1 mutant was more significant.3.The expression of HGO,MAAI,and SSCD1 genes were significantly up-regulated in the tyrosine degradation pathway after treatment with phenylalanine.Furthermore,the up-regulation of HGO and MAAI gene expression was more pronounced in sscd1 mutants.4.Phenylalanine could induce the accumulation of anthocyanin in Arabidopsis,and the anthocyanin accumulation on sscd1 mutant was more significant.Further analysis showed that the treatment of phenylalanine could increase the expression of upstream and downstream genes in the pathway of anthocyanin biosynthesis,and the up-regulated range was more significant in the sscd1 mutant.The study found a cross link between phenylalanine and tyrosine degradation in plants.Also,it is of great scientific significance for the in-depth study of tyrosine degradation pathways in plants.