Membrane steroid-binding protein 1 induced by a diffusible fungal signal is critical for mycorrhization in Medicago truncatula

authored by

Hannah Kuhn, Helge Küster, Natalia Requena

Abstract

Arbuscular mycorrhiza (AM) is a mutualistic biotrophic association that requires a complex exchange of signals between plant and fungus to allow accommodation of the mycosymbiont in the root cortex. Signal exchange happens even before physical contact, activating the plant symbiotic program. We investigated very early transcriptional responses in Medicago truncatula to inoculation with Glomus intraradices and identified four genes induced by diffusible AM fungal signals before contact. Three of them were previously shown to be mycorrhiza induced at later stages of the symbiosis, while MtMSBP1, encoding a membrane-bound steroid-binding protein, is a novel mycorrhizal marker. Expression analyses in plants defective in the symbiotic receptor kinase DMI2 allowed discrimination of two different signaling cascades involved in the perception of the diffusible signals. Thus, while some of the genes are activated in a DMI2-dependent manner, the induction of one of them encoding a proteinase inhibitor is DMI2-independent. Downregulation of MtMSBP1 by RNAi led to an aberrant mycorrhizal phenotype with thick and septated appressoria, decrease number of arbuscules and distorted arbuscule morphology. This provides genetic evidence that MtMSBP1 is critical for mycorrhiza development. We hypothesize that MtMSBP1 plays a role in sterol homeostasis in the root.

Organisation(s)

Section Plant Genomics
Institute of Plant Genetics

External Organisation(s)

Karlsruhe Institute of Technology (KIT)

Type

Article

Journal

New Phytologist

Volume

185

Pages

716-733

No. of pages

18

ISSN

0028-646X

Publication date

01.02.2010

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Physiology, Plant Science

Electronic version(s)

https://doi.org/10.1111/j.1469-8137.2009.03116.x (Access: Unknown)