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Extended hopanoid lipids promote bacterial motility, surface attachment, and root nodule development in the Bradyrhizobium diazoefficiens-Aeschynomene afraspera symbiosis

Belin, Brittany J. and Tookmanian, Elise T. and de Anda, Jaime and Wong, Gerard and Newman, Dianne K. (2018) Extended hopanoid lipids promote bacterial motility, surface attachment, and root nodule development in the Bradyrhizobium diazoefficiens-Aeschynomene afraspera symbiosis. . (Unpublished) http://resolver.caltech.edu/CaltechAUTHORS:20180927-114224832

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Abstract

Hopanoids are steroid-like bacterial lipids that enhance membrane rigidity and promote bacterial growth under diverse stresses. Roughly 10% of bacteria contain genes involved in hopanoid biosynthesis, and these genes are particularly conserved in plant-associated organisms. We previously found that the extended class of hopanoids (C35) in the nitrogen-fixing soil bacterium Bradyrhizobium diazoefficiens promotes its root nodule symbiosis with the tropical legume Aeschynomene afraspera. By quantitatively modeling root nodule development, we identify independent roles for hopanoids in the initiation of root nodule formation and in determining the rate of root nodule maturation. In vitro studies demonstrate that extended hopanoids support B. diazoefficiens motility and surface attachment, which may correlate with stable root colonization in planta. Confocal microscopy of maturing root nodules reveals that root nodules infected with extended hopanoid-deficient B. diazoefficiens contain unusually low densities of bacterial symbionts, indicating that extended hopanoids are necessary for persistent, high levels of host infection. This work identifies extended hopanoids as regulators of the efficiency of Bradyrhizobia nitrogen-fixing symbioses, agriculturally and economically significant associations with growing importance in a changing climate.


Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription
https://doi.org/10.1101/423301DOIDiscussion Paper
ORCID:
AuthorORCID
Newman, Dianne K.0000-0003-1647-1918
Additional Information:The copyright holder for this preprint is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-ND 4.0 International license. This work was supported by grants from the HHMI (D.K.N.), NASA (NNX12AD93G, D.K.N.), Jane Coffin Childs Memorial Fund (B.J.B.), NIH (K99GM126141, B.J.B.), and Ford Foundation Predoctoral Fellowship (J.d.A.), and Army Research Office (W911NF-18-1-0254, GW). We thank Dr. Eric Giraud for his generous gift of A. afraspera seeds and training on Aeschynomene symbioses and Drs. Hans-Martin Fischer and Raphael Ledermann for plasmids and technical advice for the genetic transformation of B. diazoefficiens. Dr. Nathan Dalleska of the Environmental Analysis Center at Caltech was instrumental in providing training and support for GC-MS analysis of acetylene reduction. We are grateful to Dr. Gargi Kulkarni and other members of the Newman lab, as well as Drs. Elliot Meyerowitz and Rob Phillips, for their collegiality and thoughtful discussions about this work. We are indebted to Ms. Shannon Park and Ms. Kristy Nguyen for providing the administrative assistance that allows us to focus on our research.
Funders:
Funding AgencyGrant Number
Howard Hughes Medical Institute (HHMI)UNSPECIFIED
NASANNX12AD93G
Jane Coffin Childs Memorial Fund for Medical ResearchUNSPECIFIED
NIHK99GM126141
Ford FoundationUNSPECIFIED
Army Research Office (ARO)W911NF-18-1-0254
Record Number:CaltechAUTHORS:20180927-114224832
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20180927-114224832
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:90009
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:27 Sep 2018 20:58
Last Modified:27 Sep 2018 20:58

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