Land plants evolved from charophytic algae, among which Charophyceae possess the most complex body plans. We present the genome of Chara braunii; comparison of the genome to those of land plants identified evolutionary novelties for plant terrestrialization and land plant heritage genes. C. braunii employs unique xylan synthases for cell wall biosynthesis, a phragmoplast (cell separation) mechanism similar to that of land plants, and many phytohormones. C. braunii plastids are controlled via land-plant-like retrograde signaling, and transcriptional regulation is more elaborate than in other algae. The morphological complexity of this organism may result from expanded gene families, with three cases of particular note: genes effecting tolerance to reactive oxygen species (ROS), LysM receptor-like kinases, and transcription factors (TFs). Transcriptomic analysis of sexual reproductive structures reveals intricate control by TFs, activity of the ROS gene network, and the ancestral use of plant-like storage and stress protection proteins in the zygote.
- Klíčová slova
- Chara, Phragmoplastophyta, charophyte, phragmoplast, phytohormones, plant evolution, reactive oxygen species, streptophyte, transcriptional regulation,
- MeSH
- biologická evoluce MeSH
- buněčná stěna metabolismus MeSH
- Chara genetika růst a vývoj MeSH
- genom rostlinný * MeSH
- genové regulační sítě MeSH
- pentosyltransferasy genetika MeSH
- protein-serin-threoninkinasy genetika metabolismus MeSH
- reaktivní formy kyslíku metabolismus MeSH
- regulátory růstu rostlin metabolismus MeSH
- rostlinné proteiny genetika metabolismus MeSH
- transkripční faktory genetika metabolismus MeSH
- transkriptom MeSH
- vyšší rostliny genetika MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
- Názvy látek
- 1,4-beta-D-xylan synthase MeSH Prohlížeč
- pentosyltransferasy MeSH
- protein-serin-threoninkinasy MeSH
- reaktivní formy kyslíku MeSH
- regulátory růstu rostlin MeSH
- rostlinné proteiny MeSH
- transkripční faktory MeSH
While the molecular basis for cytokinin action is quite well understood in flowering plants, little is known about the cytokinin signal transduction in early diverging land plants. The genome of the bryophyte Physcomitrella patens (Hedw.) B.S. encodes three classical cytokinin receptors, the CHASE domain-containing histidine kinases, CHK1, CHK2, and CHK3. In a complementation assay with protoplasts of receptor-deficient Arabidopsis thaliana as well as in cytokinin binding assays, we found evidence that CHK1 and CHK2 receptors can function in cytokinin perception. Using gene targeting, we generated a collection of CHK knockout mutants comprising single (Δchk1, Δchk2, Δchk3), double (Δchk1,2, Δchk1,3, Δchk2,3), and triple (Δchk1,2,3) mutants. Mutants were characterized for their cytokinin response and differentiation capacities. While the wild type did not grow on high doses of cytokinin (1 µM benzyladenine), the Δchk1,2,3 mutant exhibited normal protonema growth. Bud induction assays showed that all three cytokinin receptors contribute to the triggering of budding, albeit to different extents. Furthermore, while the triple mutant showed no response in this bioassay, the remaining mutants displayed budding responses in a diverse manner to different types and concentrations of cytokinins. Determination of cytokinin levels in mutants showed no drastic changes for any of the cytokinins; thus, in contrast to Arabidopsis, revealing only small impacts of cytokinin signaling on homeostasis. In summary, our study provides a first insight into the molecular action of cytokinin in an early diverging land plant and demonstrates that CHK receptors play an essential role in bud induction and gametophore development.
- Klíčová slova
- Bryophyte, Physcomitrella patens, cytokinin, cytokinin receptor, evolution, moss, phytohormone, plant growth regulator, signaling, two-component system.,
- MeSH
- biotest MeSH
- butadieny farmakologie MeSH
- cytokininy farmakologie MeSH
- fenotyp MeSH
- fyziologická adaptace MeSH
- genový knockout MeSH
- hemiterpeny farmakologie MeSH
- mechy účinky léků genetika metabolismus MeSH
- mutace genetika MeSH
- pentany farmakologie MeSH
- receptory buněčného povrchu chemie metabolismus MeSH
- regulace genové exprese u rostlin MeSH
- rostlinné proteiny chemie metabolismus MeSH
- terciární struktura proteinů MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- butadieny MeSH
- cytokininy MeSH
- hemiterpeny MeSH
- isoprene MeSH Prohlížeč
- pentany MeSH
- receptory buněčného povrchu MeSH
- rostlinné proteiny MeSH
Cytokinins, a class of phytohormones, are adenine derivatives common to many different organisms. In plants, these play a crucial role as regulators of plant development and the reaction to abiotic and biotic stress. Key enzymes in the cytokinin synthesis and degradation in modern land plants are the isopentyl transferases and the cytokinin dehydrogenases, respectively. Their encoding genes have been probably introduced into the plant lineage during the primary endosymbiosis. To shed light on the evolution of these proteins, the genes homologous to plant adenylate isopentenyl transferase and cytokinin dehydrogenase were amplified from the genomic DNA of cyanobacterium Nostoc sp. PCC 7120 and expressed in Escherichia coli. The putative isopentenyl transferase was shown to be functional in a biochemical assay. In contrast, no enzymatic activity was detected for the putative cytokinin dehydrogenase, even though the principal domains necessary for its function are present. Several mutant variants, in which conserved amino acids in land plant cytokinin dehydrogenases had been restored, were inactive. A combination of experimental data with phylogenetic analysis indicates that adenylate-type isopentenyl transferases might have evolved several times independently. While the Nostoc genome contains a gene coding for protein with characteristics of cytokinin dehydrogenase, the organism is not able to break down cytokinins in the way shown for land plants.
- MeSH
- biologická evoluce MeSH
- cytokininy metabolismus MeSH
- Escherichia coli enzymologie růst a vývoj MeSH
- fylogeneze MeSH
- geneticky modifikované rostliny genetika růst a vývoj metabolismus MeSH
- molekulární sekvence - údaje MeSH
- mutace genetika MeSH
- mutageneze cílená MeSH
- Nostoc enzymologie genetika MeSH
- oxidoreduktasy genetika metabolismus MeSH
- prenyltransferáza genetika metabolismus MeSH
- regulace genové exprese enzymů MeSH
- rekombinantní proteiny metabolismus MeSH
- sekvence aminokyselin MeSH
- sekvenční homologie aminokyselin MeSH
- tabák enzymologie růst a vývoj MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- cytokinin oxidase MeSH Prohlížeč
- cytokininy MeSH
- oxidoreduktasy MeSH
- prenyltransferáza MeSH
- rekombinantní proteiny MeSH
