||The plant hormone ethylene plays a dual-and-opposing role in regulation of shoot gravitropism in light-grown plant. A long-term ethylene pretreatment is required for promoting hypocotyls gravitropic response in light-grown seedlings. Ethylene-dependent gravitropism-deficient yellow-green (egy1) mutant was isolated based on defects in both ethylene-dependent hypocotyls gravitropism and yellow-green cotyledon phenotype. The chloroplast and amyloplast development in this mutant are severely impaired. The chlorophyll content, light harvesting complex proteins (LHCP) and starch decrease severely in egy1. EGY1 gene encodes a plastid-localized, membrane-bound metalloprotease. To identify the putative substrates of EGY1, we took degradomics approach and compared the total chloroplast proteins of egy1 with that of wild type. It is believed that the accumulated plastid proteins in egy1 may serve either as the direct or indirect putative substrates for EGY1 protease. Thus far, a large number of chloroplast proteins have been identified to accumulate in egy1 plastid. Glutamate synthase 1 and 2 have been verified by Western blot. Another approach we took was to pull down the substrates from egy1 mutant by a mutated EGY1 protein without function and it is still under investigation.