PD Dr. Klaus von Schwartzenberg
Welcome
Our group is studying mechanisms of plant growth regulation focusing on the classical phytohormone cytokinin. We address the analysis of cytokinin biosynthesis, metabolism and perception and carry out most of our work with the bryophyte model organism Phycomitrella patens. We are also interested to study growth control in streptophytic algae (Zygnematophyceae).
Biochemical methods as well as the generation of transgenic plants (knockout plants, overexpressors) are applied to obtain information about gene function.
Projects
Cytokinin biosynthesis
Soon after the dicovery of cytokinins, it was demonstrated that these plant hormones have devopmental effects on bryophytes as early divergent land plants (review Schwartzenberg 2009). In floweing plants two major pathways exist for the biogenesis of cytokinins (Miyawaki et al. 2006):
(a) de novo biosynthesis using adenylate isopentenyltransferases (IPTs) which transfer a isoprene group to AMP, ADP or ATP;
(b) tRNA-IPTs which isoprenylate specific adenosine residues of certain tRNAs (Fig).
In the genome of Physcomitrella so far only tRNA-IPTs have been found, which we functionally characterise (Yevdakova et al. 2007, 2008). We study in which points cytokinin biosynthesis and its regulation differ between mosses and flowering plants. Our results provide evidence that the complex IPT multigene family in Physcomitrella might be related to a functional diversification (Lindner et al. 2014).
Fig. Scheme of cytokinin biosynthesis in flowering plants.
References
Lindner, Ann-Cathrin, Daniel Lang, Maike Seifert, Kateřina Podlešáková, Ondřej Novák, Miroslav Strnad, Ralf Reski, and Klaus von Schwartzenberg. 2014. "Isopentenyltransferase-1 (IPT1) Knockout in Physcomitrella together with phylogenetic analyses of IPTs provide insights into evolution of plant cytokinin biosynthesis". Journal of Experimental Botany 65: 2533-2543.
Miyawaki, Kaori, Petr Tarkowski, Miho Matsumoto-Kitano, Tomohiko Kato, Shusei Sato, Danuse Tarkowska, Satoshi Tabata, Göran Sandberg, und Tatsuo Kakimoto. 2006. "Roles of Arabidopsis ATP/ADP isopentenyltransferases and tRNA isopentenyltransferases in cytokinin biosynthesis". Proceedings of the National Academy of Sciences 103: 16598 -16603.
Patil, Gunvant, Nicander, Björn. 2013. “Identification of two additional members of the tRNA isopentenyltransferase family in Physcomitrella patens”. Plant Molecular Biology 82: 417–426.
Schwartzenberg v., Klaus. "Hormonal Regulation of Development by Auxin and Cytokinin in Moss". Annual Plant Reviews 36: 246-281. doi:10.1002/9781444316070.ch10.
Yevdakova, Natalya A, und Klaus von Schwartzenberg. 2007. "Characterisation of a prokaryote-type tRNA-isopentenyltransferase gene from the moss Physcomitrella patens". Planta 226: 683-695.
Yevdakova, Natalya A., Václav Motyka, Jiri Malbeck, Alena Trávnícková, Ondrej Novák, Miroslav Strnad, und Klaus v. Schwartzenberg. 2008. "Evidence for importance of tRNA-dependent cytokinin biosynthetic pathway in the moss Physcomitrella patens". Journal of Plant Growth Regulation 27: 271-281.
Cytokinin perception
Genomic analysis has shown that Physcomitrella contains all major components of cytokinin signal transduction including CRE-type receptors, which contain the typical CHASE- domain (Rensing et. al. 2008, Pils and Heyl, 2009).
We dispose of knock-out plants for all three CRE genes and are currently analysing their specific impact on gene expression, development and metabolism in Physcomitrella (Schwartzenberg et al. 2016).
Fig. Simplified scheme of cytokinin signal transduction.
References
Pils, Birgit, und Alexander Heyl. 2009. "Unraveling the evolution of cytokinin signaling". Plant Physiology 151: 782 -791.
Rensing, Stefan A., Daniel Lang, Andreas D. Zimmer, Astrid Terry, Asaf Salamov, Harris Shapiro, Tomoaki Nishiyama, et al. 2008. "The Physcomitrella genome reveals evolutionary insights into the conquest of land by plants". Science 319: 64-69.
Schwartzenberg v. K, Lindner A.-C., Gruhn N., Šimura J., Novák O., Strnad M., Gonneau M., Nogué F., Heyl A.:
CHASE domain-containing receptors play an essential role in the cytokinin response of the moss Physcomitrella patens. J Exp Botany 67, 667-679 (2016), http://jxb.oxfordjournals.org/content/early/2015/11/22/jxb.erv479.full.pdf+html
Cytokinin- und purine interconversion
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For the metabolic interconversion of cytokinins between the forms of bases, nucleosides and nucleotides plants use either cytokinin specific enzymes like cytokinin nucleotide phosphoribohydrolase (Kurakawa et al. 2007) or enzymes from adenylate interconversion like adenosine kinase (Schwartzenberg et al. 1998, Schoor et al. 2011), adenine phosphoribosyltransferase (Allen et al. 2002) or nucleoside hydrolase (NRHs) (Jung et al. 2011). We are studying cytokinin/adenlyate interconversion and presented a comprehensive analysis on NRHs in Physcomitrella and maize including enzyme kinetics, crystal structures and mutant characterization (Kopečná et al. 2013). |
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Fig. Simplified scheme of cytokinin interconversion. |
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References Allen, Michael, Wensheng Qin, François Moreau and Barbara Moffatt. 2002. "Adenine phosphoribosyltransferase isoforms of Arabidopsis and their potential contributions to adenine and cytokinin metabolism". Physiologia Plantarum 115: 56-68. Jung, Benjamin, Christiane Hoffmann and Torsten Möhlmann. 2011. "Arabidopsis nucleoside hydrolases involved in intracellular and extracellular degradation of purines". The Plant Journal 65: 703-711. Kopečná, Martina, Hanna Blaschke, David Kopečný, Armelle Vigouroux, Radka Končitíková, Ondřej Novák, Ondřej Kotland, Miroslav Strnad, Solange Moréra and Klaus von Schwartzenberg. 2013. “Structure and function of nucleoside hydrolases from Physcomitrella patens and maize catalyzing the hydrolysis of purine, pyrimidine, and cytokinin ribosides”. Plant Physiology 163, 1568-1583. Kurakawa, Takashi, Nanae Ueda, Masahiko Maekawa, Kaoru Kobayashi, Mikiko Kojima, Yasuo Nagato, Hitoshi Sakakibara and Junko Kyozuka. 2007. "Direct control of shoot meristem activity by a cytokinin-activating enzyme". Nature: 652-655. Schoor, Sarah, Scott Farrow, Hanna Blaschke, Sanghyun Lee, Gregory Perry, Klaus von Schwartzenberg, Neil Emery and Barbara Moffatt. 2011."Adenosine Kinase Contributes to Cytokinin Interconversion in Arabidopsis." Plant Physiology 157: 659-72. Schwartzenberg von, Klaus., Sven Kruse, Ralf Reski, Barbara Moffatt and Michel Laloue. 1998. "Cloning and characterization of an Adenosine Kinase from Physcomitrella Involved in Cytokinin Metabolism." The Plant Journal 13: 249-257. |