title: Plant growth promotion by Bacillus megaterium involves cytokinin signaling.
abstract: Accumulating evidence indicates that plant growth promoting rhizobacteria (PGPR) influence plant growth and development by the production of phytohormones such as auxins, gibberellins, and cytokinins. Little is known on the genetic basis and signal transduction components that mediate the beneficial effects of PGPRs in plants. We recently reported the identification of a Bacillus megaterium strain that promoted growth of A. thaliana and P. vulgaris seedlings. In this addendum, the role of cytokinin signaling in mediating the plant responses to bacterial inoculation was investigated using A. thaliana mutants lacking one, two or three of the putative cytokinin receptors CRE1, AHK2 and AHK3, and RPN12 a gene involved in cytokinin signaling. We show that plant growth promotion by B. megaterium is reduced in AHK2-2 single and double mutant combinations and in RPN12. Furthermore, the triple cytokinin-receptor CRE1-12/AHK2-2/AHK3-3 knockout was insensitive to inoculation in terms of growth promotion and root developmental responses. Our results indicate that cytokinin receptors play a complimentary role in plant growth promotion by B. megaterium.
authors.affiliation: Instituto de Investigaciones Químico-Biológicas; Universidad Michoacana de San Nicolás de Hidalgo; Morelia, Michoacán, México.
authors.forename: Randy
authors.initials: R
authors.lastname: Ortíz-Castro
authors.forename: Eduardo
authors.initials: E
authors.lastname: Valencia-Cantero
authors.forename: José
authors.initials: J
authors.lastname: López-Bucio
references.citation: Ann Bot. 2006 May;97(5):883-93
references.pmid: 16473866
references.citation: Plant Cell. 2004 Jun;16(6):1365-77
references.pmid: 15155880
references.citation: Science. 2006 Jan 6;311(5757):94-8
references.pmid: 16400151
references.citation: Curr Opin Plant Biol. 2001 Aug;4(4):343-50
references.pmid: 11418345
references.citation: Planta. 2001 Jan;212(2):190-8
references.pmid: 11216839
references.citation: Proc Natl Acad Sci U S A. 2004 Jun 8;101(23):8821-6
references.pmid: 15166290
references.citation: Plant Cell. 1996 Aug;8(8):1225-37
references.pmid: 8776893
references.citation: Can J Microbiol. 2001 May;47(5):404-11
references.pmid: 11400730
references.citation: Plant Cell Environ. 2006 May;29(5):909-18
references.pmid: 17087474
references.citation: Annu Rev Plant Biol. 2003;54:605-27
references.pmid: 14503005
references.citation: Proc Natl Acad Sci U S A. 2003 Apr 15;100(8):4927-32
references.pmid: 12684534
references.citation: Plant Cell. 2002 Jan;14(1):17-32
references.pmid: 11826296
references.citation: Mol Plant Microbe Interact. 2007 Feb;20(2):207-17
references.pmid: 17313171