Group Leader: Josep Maria Torné (CSIC Research Professor)
Researchers: Mireia Santos
PhD Students: Nefertiti Campos (until september 2013), Jordi Gibert (until december 2012), Oriol Lopera (until december 2012)
Role of plastidial transglutaminase-TGZ in chloroplast thylakoidal membranes and photosynthesis related processes.
The studies related to the enzyme transglutaminase (TGase) have been the main aim of the group. This enzyme catalyzes post-translational modifications of proteins through covalent linkage of substrates with primary amino groups. TGases are widely distributed and play a fundamental role in cellular differentiation, tissue stabilization and apoptosis. The most studied TGases are that of human and animal origin, i.e. human blood coagulation factor XIII (fibrin-stabilizing factor) while studies involving plants TGase are very scarce.
The group accomplished, for the first time in plants, the cloning of two cDNAs that codify for maize chloroplast TGase (tgz). We had demonstrated that this enzyme is stimulated by light and preferably located in the grana of the differentiated chloroplasts, and coinmunolocalized with the light–harvesting antenna proteins (Lhcb) during the greening process of chloroplast differentiation. We have shown the involvement of bound PAs by means of TGase activity in the photo protection of the phothosynthetic apparatus, when an excess of light intensity could damage the plant.
Recently, we report the remodelling of tobacco thylakoids by over-expression of maize plastidial TGZ. In tobacco over-expressers, an increase of the PSII centers located in grana thylakoids (PSIIα) at the expense of PSII centers located mainly in stroma thylakoids (PSIIβ) has been described. We provide evidences indicating that grana remodelling may be possible through over-expression of a single enzyme, and suggesting that tgz has an important functional role in grana stacking and photoprotection. As a collaboration project, we have transformed A.thaliana plants with the tgz gene to study the modification of the transformed plants with respect to photosystem protein complexes variations and photo-phluorescence parameters, during different light treatments
Finally, we have cloned a new TGase: rice TGase (TGO), that has been subcellular immunolacalized in the chloroplasts and in the bulliform cells wall. TGO over-expression in E.coli has permitted the enzyme characterization. In vitro proteomic assays and transcriptomic in vivo Dynamic array (FluidigmTM) analysis in rice plants submitted to different continuous illumination periods indicated that there was a gene-dependent tendency in the expression pattern that in some cases is related to tgo expression and to the illumination cycle. TGO was related specially to proteins implicated in photoprotection and in thylakoid electrochemical gradient. These relationships seem to be also connected with the day/night cycling of gene expression, suggesting that tgo expression might be regulated in a similar manner as in circadian genes, perhaps through the mRNA expression of its own substrates (such antenna proteins, PsbS, etc.).
- Rice transformation with the tgz gene to identify its signal chloroplast peptide. This project has demonstrated that TGZ has a real chloroplast signal peptide that drives the protein to the chloroplast.
- In collaboration with D.Eduard Barberá (IQS, Barcelona, Spain) theTGZ over-expression, characterization and purification in Pichia pastoris was performed.
- A. thaliana transformation with the tgz gene: as a collaboration project with Dr.Kotzabasis group (Univ. Creta, Greece), we have transformed A. thaliana plants with the tgz gene to study the modification of the transformed plants with respect to polyamine composition, photosystem protein complexes variations and photo-phluorescence parameters, during different light treatments.
- As part of a project to characterize new TGases in plant species, the identification, cloning and biochemical characterization of the transglutaminase gene (tgo) in rice (Oryza sativa) was realized. This project was ejecuted in collaboration with the Dr. Sonia castañón (Neiker Technalia, Vitoria, Spain).
Campos, N., Castañón, S., Urreta, I., Santos, M., Torné, J.M.
Rice transglutaminase gene: Identification, protein expression, functionality, light dependence and specific cell location.
(2013) Plant Science 205-206, pp. 97-110.
Ioannidis, N.E., Lopera, O., Santos, M., Torné, J.M., Kotzabasis, K.
Role of plastid transglutaminase in LHCII polyamination and thylakoid electron and proton flow
(2012) PLoS ONE 7 (7), e41979
N.Campos, E.Villalobos, P.Fontanet, J.M.Torné, M.Santos
A peptide of 17 aminoacids from the N-terminal region of maize plastidial transglutaminase is essential for chloroplast targeting
(2012) Am. J. Mol. Biol. 2, pp.245-247.
N. E. Ioannidis, J.M.Torné, K. Kotzabasis and M. Santos.
Transglutaminase is Involved in the Remodeling of Tobacco Thylakoids
(2012) In: Advances in Photosynthesis – Fundamental Aspects. Chap.25. pp.519-538. Ed. by M. Mahdi. ISBN 978-953-307-928-8.