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Planta (2012) 236:491511DOI 10.1007/s00425-012-1627-9
ORIGINAL ARTICLE
A Ser/Thr protein kinase phosphorylates MA-ACS1 (Musa acuminata 1-aminocyclopropane-1-carboxylic acid synthase 1) during banana fruit ripening
Swarup Roy Choudhury Sujit Roy Dibyendu N. Sengupta
Received: 17 October 2011 / Accepted: 24 February 2012 / Published online: 15 March 2012 Springer-Verlag 2012
Abstract 1-Aminocyclopropane-1-carboxylic acid synthase (ACS) catalyzes the rate-limiting step in ethylene bio-synthesis during ripening. ACS isozymes are regulated both transcriptionally and post-translationally. However, in banana, an important climacteric fruit, little is known about post-translational regulation of ACS. Here, we report the post-translational modiWcation of MA-ACS1 (Musa acuminata ACS1), a ripening inducible isozyme in the ACS family, which plays a key role in ethylene biosynthesis during banana fruit ripening. Immunoprecipitation analyses of phospholabeled protein extracts from banana fruit using aYnity-puriWed anti-MA-ACS1 antibody have revealed phosphorylation of MA-ACS1, particularly in ripe fruit tissue. We have identiWed the induction of a 41-kDa protein
kinase activity in pulp at the onset of ripening. The 41-kDa protein kinase has been identiWed as a putative protein kinase by MALDITOF/MS analysis. Biochemical analyses using partially puriWed protein kinase fraction from banana fruit have identiWed the protein kinase as a Ser/Thr family of protein kinase and its possible involvement in MA-ACS1 phosphorylation during ripening. In vitro phosphorylation analyses using synthetic peptides and site-directed mutagenized recombinant MA-ACS1 have revealed that serine 476 and 479 residues at the C-terminal region of MA-ACS1 are phosphorylated. Overall, this study provides important novel evidence for in vivo phosphorylation of MA-ACS1 at the molecular level as a possible mechanism of post-translational regulation of this key regulatory protein in ethylene signaling pathway in banana fruit during ripening.
Keywords ACC synthase Ethylene MAP kinase Musa Phosphorylation Ripening
Abbreviations
ACC 1-Aminocyclopropane-1-carboxylic acid ACS ACC synthaseCPZ ChlorpromazineDAH Days after harvestDPA Days post-anthesisPAO Phenylarsine oxidePEG Polyethylene glycolTFP TriXuoperazine
Introduction
ACC synthase (EC: 4.4.1.14) (ACS), which catalyzes the conversion of AdoMet (S-adenosyl-L-methionine) to ACC
S. R. Choudhury and S. Roy have contributed equally to this work.
Electronic supplementary material The online version of this article (doi:http://dx.doi.org/10.1007/s00425-012-1627-9
Web End =10.1007/s00425-012-1627-9 ) contains supplementary material, which is available to authorized users.
S. R. Choudhury D. N. SenguptaDivision of Plant Biology, Bose Institute, 93/1, Acharya Prafulla Chandra Road, Kolkata 700 009, West Bengal, India
Present Address:S. R. Choudhury (&)
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