Functional Analysis Of FtsH12 Protease On Regulation Of Chloroplast Development Of Arabidopsis

FtsHs(Filamentation temperature-sensitive H)are a well-characterized family of membrane bound proteases containing an AAA(ATPase associated with various cellular activities)and a Zn2+ metalloprotease domains.FtsH proteases are general found in fungi,animals and plants and are known to have a crucial role in housekeeping proteolysis of membrane proteins.In Arabidopsis thaliana,17 FtsH family members are present(FtsH 1-12 and FtsHi 1-5)and their subcellular localization is restricted to mitochondria and chloroplasts.FtsH 1,2,5 and 8 localized in the thylakoid membrane and known for their importance in photosynthesis.Here,we isolate the Arabidopsis T-DNA insertion mutants of FtsH12.We show that the embryo development with the globular to heart transition stage arrested in this mutant,thus leading to embryo lethality.Transmission electron microscopic analysis reveals the absence of normal chloroplast development in the mutant embryos with a failure to form thylakoids.Subcelluar localization study with western blot using anti-FtsH 12 antibodies shows that FtsH 12 are localized in the chloroplast thylakoid membrane.Blue-native PAGE and sucrose density gradient centrifugation come with wesrern boltting analyse suggest that FtsH12 proteins may form a protein complex to control chloroplast formation.These above results indicate that FtsH 12 is involved in chloroplast biogenesis during embryogenesis in Arabidopsis.Therefore,we deduce that the FtsH 12 protease maybe involed in the early development of Arabidopsis chloroplast.