Effects Of Homogentisate On Tyrosine Degradation Pathway In Arabidopsis Thaliana

Tyrosine degradation is an essential metabolic pathway in animals,but it is not clear in plants.The tyrosine degradation pathway involves a five-step reaction.Previous studies in Arabidopsis found that the gene mutation,encoding the last enzyme of the SSCD1,led to the plant death under short day but was not affected under long day.Homogentisate is produced by the second step of tyrosine degradation pathway,and is also the precursor of vitamin E synthesis in plants.To investigate whether tyrosine degradation pathway functions in Arabidopsis under long day.we used the tyrosine pathway-deficient mutant sscd1,hgo and the wild type Col-0 of Arabidopsis thaliana as the materials,observed the effects of homogentisate on seeds germination,seedling growth and anthocyanin accumulation.The results showed that:1.Homogentisate(0.4 mM-0.8 mM)induced the death of sscd1 mutant under long day.2.Homogentisate up regulated the expression of HGO and MAAI genes in tyrosine degradation pathway in sscd1 mutant.3.Certain amount of homogentisate delayed the germination of sscd1 mutant seeds,but had no effect on the seeds germination of the wild type and hgo mutant,and the exogenous succinylacetone treatment inhibited the seed germination of wild type Arabidopsis.3.Certain amount of homogentisate delayed the germination of sscd1 mutant seeds,but had no effect on the germination of wild-type and hgo mutant seeds;exogenous succinylacetone inhibited seed germination of wild-type Arabidopsis.4.High concentration of sucrose(3%-5%)could increase the effect of homogentisate on the germination of sscd1 mutant seeds,but reduced the impact of homogentisate on the death in sscd1 mutant.5.Homogentisate increased the accumulation anthocyanins in sscd1 mutant,and increased the expression of upstream genes PAL,CHI,CHS and downstream genes DFR,LDOX and UF3 GT in the anthocyanin biosynthesis of Arabidopsis.