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Qin L, Bdira FB, Sterckx YGJ, Volkov AN, Vreede J, Giachin G, van Schaik P, Ubbink M, Dame RT. Structural basis for osmotic regulation of the DNA binding properties of H-NS proteins. Nucleic Acids Res 2020; 48:2156-2172. [PMID: 31925429 PMCID: PMC7039000 DOI: 10.1093/nar/gkz1226] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 11/29/2019] [Accepted: 12/19/2019] [Indexed: 01/07/2023] Open
Abstract
H-NS proteins act as osmotic sensors translating changes in osmolarity into altered DNA binding properties, thus, regulating enterobacterial genome organization and genes transcription. The molecular mechanism underlying the switching process and its conservation among H-NS family members remains elusive. Here, we focus on the H-NS family protein MvaT from Pseudomonas aeruginosa and demonstrate experimentally that its protomer exists in two different conformations, corresponding to two different functional states. In the half-opened state (dominant at low salt) the protein forms filaments along DNA, in the fully opened state (dominant at high salt) the protein bridges DNA. This switching is a direct effect of ionic strength on electrostatic interactions between the oppositely charged DNA binding and N-terminal domains of MvaT. The asymmetric charge distribution and intramolecular interactions are conserved among the H-NS family of proteins. Therefore, our study establishes a general paradigm for the molecular mechanistic basis of the osmosensitivity of H-NS proteins.
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Affiliation(s)
- Liang Qin
- Department of Macromolecular Biochemistry, Leiden Institute of Chemistry, Einsteinweg 55, 2333 CC Leiden, the Netherlands.,Centre for Microbial Cell Biology, Leiden University, Einsteinweg 55, 2333CC Leiden, the Netherlands
| | - Fredj Ben Bdira
- Department of Macromolecular Biochemistry, Leiden Institute of Chemistry, Einsteinweg 55, 2333 CC Leiden, the Netherlands.,Centre for Microbial Cell Biology, Leiden University, Einsteinweg 55, 2333CC Leiden, the Netherlands
| | - Yann G J Sterckx
- Laboratory of Medical Biochemistry, University of Antwerp, Campus Drie Eiken, University Square 1, 2610 Wilrijk, Belgium
| | - Alexander N Volkov
- VIB-VUB Structural Biology Research Center, Pleinlaan 2, 1050 Brussels, Belgium.,Jean Jeener NMR Centre, VUB, Pleinlaan 2, 1050 Brussels, Belgium
| | - Jocelyne Vreede
- Department of Computational Chemistry, Van't Hoff Institute for Molecular Sciences, University of Amsterdam Science Park 904, 1098 XH Amsterdam, the Netherlands
| | - Gabriele Giachin
- Structural Biology Group, European Synchrotron Radiation Facility (ESRF), Grenoble, France
| | - Peter van Schaik
- Department of Macromolecular Biochemistry, Leiden Institute of Chemistry, Einsteinweg 55, 2333 CC Leiden, the Netherlands.,Centre for Microbial Cell Biology, Leiden University, Einsteinweg 55, 2333CC Leiden, the Netherlands
| | - Marcellus Ubbink
- Department of Macromolecular Biochemistry, Leiden Institute of Chemistry, Einsteinweg 55, 2333 CC Leiden, the Netherlands
| | - Remus T Dame
- Department of Macromolecular Biochemistry, Leiden Institute of Chemistry, Einsteinweg 55, 2333 CC Leiden, the Netherlands.,Centre for Microbial Cell Biology, Leiden University, Einsteinweg 55, 2333CC Leiden, the Netherlands
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Dirks-Mulder A, Butôt R, van Schaik P, Wijnands JWPM, van den Berg R, Krol L, Doebar S, van Kooperen K, de Boer H, Kramer EM, Smets EF, Vos RA, Vrijdaghs A, Gravendeel B. Exploring the evolutionary origin of floral organs of Erycina pusilla, an emerging orchid model system. BMC Evol Biol 2017; 17:89. [PMID: 28335712 PMCID: PMC5364718 DOI: 10.1186/s12862-017-0938-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Accepted: 03/15/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Thousands of flowering plant species attract pollinators without offering rewards, but the evolution of this deceit is poorly understood. Rewardless flowers of the orchid Erycina pusilla have an enlarged median sepal and incised median petal ('lip') to attract oil-collecting bees. These bees also forage on similar looking but rewarding Malpighiaceae flowers that have five unequally sized petals and gland-carrying sepals. The lip of E. pusilla has a 'callus' that, together with winged 'stelidia', mimics these glands. Different hypotheses exist about the evolutionary origin of the median sepal, callus and stelidia of orchid flowers. RESULTS The evolutionary origin of these organs was investigated using a combination of morphological, molecular and phylogenetic techniques to a developmental series of floral buds of E. pusilla. The vascular bundle of the median sepal indicates it is a first whorl organ but its convex epidermal cells reflect convergence of petaloid features. Expression of AGL6 EpMADS4 and APETALA3 EpMADS14 is low in the median sepal, possibly correlating with its petaloid appearance. A vascular bundle indicating second whorl derivation leads to the lip. AGL6 EpMADS5 and APETALA3 EpMADS13 are most highly expressed in lip and callus, consistent with current models for lip identity. Six vascular bundles, indicating a stamen-derived origin, lead to the callus, stelidia and stamen. AGAMOUS is not expressed in the callus, consistent with its sterilization. Out of three copies of AGAMOUS and four copies of SEPALLATA, EpMADS22 and EpMADS6 are most highly expressed in the stamen. Another copy of AGAMOUS, EpMADS20, and the single copy of SEEDSTICK, EpMADS23, are most highly expressed in the stelidia, suggesting EpMADS22 may be required for fertile stamens. CONCLUSIONS The median sepal, callus and stelidia of E. pusilla appear to be derived from a sepal, a stamen that gained petal identity, and stamens, respectively. Duplications, diversifying selection and changes in spatial expression of different MADS-box genes shaped these organs, enabling the rewardless flowers of E. pusilla to mimic an unrelated rewarding flower for pollinator attraction. These genetic changes are not incorporated in current models and urge for a rethinking of the evolution of deceptive flowers.
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Affiliation(s)
- Anita Dirks-Mulder
- Endless Forms group, Naturalis Biodiversity Center, Vondellaan 55, 2332 AA, Leiden, The Netherlands.,Faculty of Science and Technology, University of Applied Sciences Leiden, Zernikedreef 11, 2333 CK, Leiden, The Netherlands
| | - Roland Butôt
- Endless Forms group, Naturalis Biodiversity Center, Vondellaan 55, 2332 AA, Leiden, The Netherlands
| | - Peter van Schaik
- Faculty of Science and Technology, University of Applied Sciences Leiden, Zernikedreef 11, 2333 CK, Leiden, The Netherlands
| | - Jan Willem P M Wijnands
- Faculty of Science and Technology, University of Applied Sciences Leiden, Zernikedreef 11, 2333 CK, Leiden, The Netherlands
| | - Roel van den Berg
- Faculty of Science and Technology, University of Applied Sciences Leiden, Zernikedreef 11, 2333 CK, Leiden, The Netherlands
| | - Louie Krol
- Faculty of Science and Technology, University of Applied Sciences Leiden, Zernikedreef 11, 2333 CK, Leiden, The Netherlands
| | - Sadhana Doebar
- Faculty of Science and Technology, University of Applied Sciences Leiden, Zernikedreef 11, 2333 CK, Leiden, The Netherlands
| | - Kelly van Kooperen
- Faculty of Science and Technology, University of Applied Sciences Leiden, Zernikedreef 11, 2333 CK, Leiden, The Netherlands
| | - Hugo de Boer
- Endless Forms group, Naturalis Biodiversity Center, Vondellaan 55, 2332 AA, Leiden, The Netherlands.,The Natural History Museum, University of Oslo, P.O. Box 1172, Blindern, 0318, Oslo, Norway.,Department of Organismal Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, Uppsala, SE-75236, Sweden
| | - Elena M Kramer
- Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Ave, Cambridge, MA, 02138, USA
| | - Erik F Smets
- Endless Forms group, Naturalis Biodiversity Center, Vondellaan 55, 2332 AA, Leiden, The Netherlands.,Ecology, Evolution and Biodiversity Conservation cluster, KU Leuven, Kasteelpark Arenberg 31, 3001, Leuven, Belgium
| | - Rutger A Vos
- Endless Forms group, Naturalis Biodiversity Center, Vondellaan 55, 2332 AA, Leiden, The Netherlands.,Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Alexander Vrijdaghs
- Ecology, Evolution and Biodiversity Conservation cluster, KU Leuven, Kasteelpark Arenberg 31, 3001, Leuven, Belgium
| | - Barbara Gravendeel
- Endless Forms group, Naturalis Biodiversity Center, Vondellaan 55, 2332 AA, Leiden, The Netherlands. .,Faculty of Science and Technology, University of Applied Sciences Leiden, Zernikedreef 11, 2333 CK, Leiden, The Netherlands. .,Institute Biology Leiden, Leiden University, Sylviusweg 72, 2333 BE, Leiden, The Netherlands.
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