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Open Access Highly Accessed Research article

Medicago truncatula and Glomus intraradices gene expression in cortical cells harboring arbuscules in the arbuscular mycorrhizal symbiosis

S Karen Gomez1, Hélène Javot13, Prasit Deewatthanawong1, Ivone Torres-Jerez2, Yuhong Tang2, Elison B Blancaflor2, Michael K Udvardi2 and Maria J Harrison1*

Author Affiliations

1 Boyce Thompson Institute for Plant Research, Tower Road, Ithaca, NY 14853, USA

2 Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA

3 CEA/Cadarache IBEB, Service de Biologie Végétale et de Microbiologie Environnementales, UMR 6191 CNRS-CEA-Aix Marseille Univ., F-13108 St. Paul Lez Durance, France

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BMC Plant Biology 2009, 9:10  doi:10.1186/1471-2229-9-10

Published: 22 January 2009

Abstract

Background

Most vascular flowering plants have the capacity to form symbiotic associations with arbuscular mycorrhizal (AM) fungi. The symbiosis develops in the roots where AM fungi colonize the root cortex and form arbuscules within the cortical cells. Arbuscules are enveloped in a novel plant membrane and their establishment requires the coordinated cellular activities of both symbiotic partners. The arbuscule-cortical cell interface is the primary functional interface of the symbiosis and is of central importance in nutrient exchange. To determine the molecular events the underlie arbuscule development and function, it is first necessary to identify genes that may play a role in this process. Toward this goal we used the Affymetrix GeneChip® Medicago Genome Array to document the M. truncatula transcript profiles associated with AM symbiosis, and then developed laser microdissection (LM) of M. truncatula root cortical cells to enable analyses of gene expression in individual cell types by RT-PCR.

Results

This approach led to the identification of novel M. truncatula and G. intraradices genes expressed in colonized cortical cells and in arbuscules. Within the arbuscule, expression of genes associated with the urea cycle, amino acid biosynthesis and cellular autophagy was detected. Analysis of gene expression in the colonized cortical cell revealed up-regulation of a lysine motif (LysM)-receptor like kinase, members of the GRAS transcription factor family and a symbiosis-specific ammonium transporter that is a likely candidate for mediating ammonium transport in the AM symbiosis.

Conclusion

Transcript profiling using the Affymetrix GeneChip® Medicago Genome Array provided new insights into gene expression in M. truncatula roots during AM symbiosis and revealed the existence of several G. intraradices genes on the M. truncatula GeneChip®. A laser microdissection protocol that incorporates low-melting temperature Steedman's wax, was developed to enable laser microdissection of M. truncatula root cortical cells. LM coupled with RT-PCR provided spatial gene expression information for both symbionts and expanded current information available for gene expression in cortical cells containing arbuscules.