The non-specific lipid transfer protein N5 of Medicago truncatulais implicated in epidermal stages of rhizobium-host interaction

BMC Plant Biology

Research Article

Simona Masiero¹  Youry Pii²  Barbara Molesini²  Tiziana Pandolfini² 

[1] Department of Biology, University of Milan, Via Celoria 26, 20133, Milan, Italy;Department of Biotechnology, University of Verona, Strada le Grazie 15, 37134, Verona, Italy;

关键词: Medicago truncatula;    MtN5;    Symbiosis;    Sinorhizobium meliloti;    Pre-infection stage;    Root hair curling;   

DOI  :  10.1186/1471-2229-12-233

 received in 2012-06-18, accepted in 2012-12-03,  发布年份 2012

来源: Springer

【 摘 要 】

BackgroundThe symbiotic interaction between leguminous plants and rhizobia involves two processes: bacterial infection, resulting in the penetration of bacteria in epidermal and cortical cells, and root nodule organogenesis. Root nodule symbiosis is activated by rhizobial signalling molecules, called Nodulation factors (NFs). NF perception induces the expression of several genes called early nodulins. The early nodulin N5 of Medicago truncatula is a lipid transfer protein that has been shown to positively regulate nodulation although it displays in vitro inhibitory activity against Sinorhizobium meliloti. The purpose of this work was to investigate the role of MtN5 by studying its spatial and temporal pattern of expression during the symbiotic interaction, also in relation to known components of the symbiotic signalling pathway, and by analysing the phenotypic alterations displayed by rhizobia-inoculated MtN5-silenced roots.ResultsWe show here that MtN5 is a NF-responsive gene expressed at a very early phase of symbiosis in epidermal cells and root hairs. MtN5 expression is induced in vitro by rhizobial effector molecules and by auxin and cytokinin, phytohormones involved in nodule organogenesis. Furthermore, lipid signaling is implicated in the response of MtN5 to rhizobia, since the activity of phospholipase D is required for MtN5 induction in S. meliloti-inoculated roots. MtN5-silenced roots inoculated with rhizobia display an increased root hair curling and a reduced number of invaded primordia compared to that in wild type roots, but with no impairment to nodule primordia formation. This phenotype is associated with the stimulation of ENOD11 expression, an early marker of infection, and with the down-regulation of Flotillin 4 (FLOT4), a protein involved in rhizobial entry.ConclusionsThese data indicate that MtN5 acts downstream of NF perception and upstream of FLOT4 in regulating pre-infection events. The positive effect of MtN5 on nodule primordia invasion is linked to the restriction of bacterial spread at the epidermal level. Furthermore, MtN5 seems to be dispensable for nodule primordia formation. These findings provide new information about the complex mechanism that controls the competence of root epidermal cells for rhizobial invasion.

【 授权许可】

Unknown   
© Pii et al.; licensee BioMed Central Ltd. 2012. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.