In conclusion, the present study has demonstrated that postharvest
application of brassinolide significantly promoted lycopene
synthesis but suppressed chlorophyll synthesis via regulating transcript
levels ofLePSY1 and LeGLK2. Moreover, ethylene production
was obviously increased by brassinolide treatment through inducing
the expression of ethylene biosynthesis related genes, including
LeACS2, LeACS4, LeACO1 and LeACO4. This effect of brassinosteroids
might be due to the promotion of ethylene synthesis to some
extent, which contributed to LePSY1 and LeGLK2 changing. According
to our investigation, the expression levels of LePSY1 and LeGLK2
changed immediately after brassinolide or brassinazole treatment,
consistent with the expression levels of ethylene synthesis genes.
Related to these, application of brassinolide significantly promoted
lycopene synthesis but suppressed chlorophyll synthesis partly
via regulating transcript levels of LePSY1 and LeGLK2 directly and
partly through ethylene synthesis. Our study, therefore, suggests
previously unknown mechanisms whereby brassinolide or brassinazole
treatments might be an effective way to control tomato fruit
ripening, at least partly via controlling fruit quality attributes and
ethylene biosynthesis