title: Remodeling of tobacco thylakoids by over-expression of maize plastidial transglutaminase.
abstract: Transglutaminases (TGases, EC 2.3.2.13) are intra- and extra-cellular enzymes that catalyze post-translational modification of proteins by establishing epsilon-(gamma-glutamyl) links and covalent conjugation of polyamines. In chloroplast it is well established that TGases specifically polyaminylate the light-harvesting antenna of Photosystem (PS) II (LHCII, CP29, CP26, CP24) and therefore a role in photosynthesis has been hypothesised (Della Mea et al. [23] and refs therein). However, the role of TGases in chloroplast is not yet fully understood. Here we report the effect of the over-expression of maize (Zea mays) chloroplast TGase in tobacco (Nicotiana tabacum var. Petit Havana) chloroplasts. The transglutaminase activity in over-expressers was increased 4 times in comparison to the wild-type tobacco plants, which in turn increased the thylakoid associated polyamines about 90%. Functional comparison between Wt tobacco and tgz over-expressers is shown in terms of fast fluorescence induction kinetics, non-photochemical quenching of the singlet excited state of chlorophyll a and antenna heterogeneity of PSII. Both in vivo probing and electron microscopy studies verified thylakoid remodeling. PSII antenna heterogeneity in vivo changes in the over-expressers to a great extent, with an increase of the centers located in grana-appressed regions (PSIIalpha) at the expense of centers located mainly in stroma thylakoids (PSIIbeta). A major increase in the granum size (i.e. increase of the number of stacked layers) with a concomitant decrease of stroma thylakoids is reported for the TGase over-expressers.
authors.affiliation: Department of Biology, University of Crete, Crete, Greece.
authors.forename: Nikolaos E
authors.initials: NE
authors.lastname: Ioannidis
authors.forename: Susana M
authors.initials: SM
authors.lastname: Ortigosa
authors.forename: Jon
authors.initials: J
authors.lastname: Veramendi
authors.forename: Marta
authors.initials: M
authors.lastname: Pintó-Marijuan
authors.forename: Isabel
authors.initials: I
authors.lastname: Fleck
authors.forename: Patricia
authors.initials: P
authors.lastname: Carvajal
authors.forename: Kiriakos
authors.initials: K
authors.lastname: Kotzabasis
authors.forename: Mireya
authors.initials: M
authors.lastname: Santos
authors.forename: José M
authors.initials: JM
authors.lastname: Torné
mesh_terms: D005453:Fluorescence; D018745:Genome, Plant; D007700:Kinetics; D008954:Models, Biological; D045332:Photosystem II Protein Complex / Q000378:metabolism; D010860:Pigments, Biological / Q000378:metabolism; D011073:Polyamines / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism* / Q000648:ultrastructure; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D011503:Transglutaminases / Q000378:metabolism*; D003313:Zea mays / Q000201:enzymology*
chemical_list: D045332:Photosystem II Protein Complex; D010860:Pigments, Biological; D011073:Polyamines; D011503:Transglutaminases