OPEN ACCESS ARTICLE

This Article Free via Open Access: OA OA Full Text Full Text (PDF) Supplemental Data OA All Versions of this Article: 151/3/1239    most recent pp.109.143933v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Google Scholar Articles by Kiss, E. Articles by Endre, G. PubMed PubMed Citation Articles by Kiss, E. Articles by Endre, G. Agricola Articles by Kiss, E. Articles by Endre, G.

LIN, a Novel Type of U-Box/WD40 Protein, Controls Early Infection by Rhizobia in Legumes^{1,[C],[W],[OA]}

Institute of Genetics, Biological Research Center, Szeged 6726, Hungary (E.K., B.O., A.B., A.L., K.K., G.E.); and Department of Disease and Stress Biology (P.K., M.M., P.M., G.E.D.O.) and Department of Molecular Microbiology (A.B.H., J.A.D.), John Innes Centre, Norwich NR4 7UH, United Kingdom

The formation of a nitrogen-fixing nodule requires the coordinated development of rhizobial colonization and nodule organogenesis. Based on its mutant phenotype, lumpy infections (lin), LIN functions at an early stage of the rhizobial symbiotic process, required for both infection thread growth in root hair cells and the further development of nodule primordia. We show that spontaneous nodulation activated by the calcium- and calmodulin-dependent protein kinase is independent of LIN; thus, LIN is not necessary for nodule organogenesis. From this, we infer that LIN predominantly functions during rhizobial colonization and that the abortion of this process in lin mutants leads to a suppression of nodule development. Here, we identify the LIN gene in Medicago truncatula and Lotus japonicus, showing that it codes for a predicted E3 ubiquitin ligase containing a highly conserved U-box and WD40 repeat domains. Ubiquitin-mediated protein degradation is a universal mechanism to regulate many biological processes by eliminating rate-limiting enzymes and key components such as transcription factors. We propose that LIN is a regulator of the component(s) of the nodulation factor signal transduction pathway and that its function is required for correct temporal and spatial activity of the target protein(s).

² Present address: Agricultural Biotechnology Centre, Gödöllö 2100, Hungary.

³ Present address: Department of Molecular Biology, University of Aarhus, 8000 Aarhus C, Denmark.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Gabriella Endre (endre{at}brc.hu).

^[C] Some figures in this article are displayed in color online but in black and white in the print edition.

^[W] The online version of this article contains Web-only data.

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.109.143933

^* Corresponding author; e-mail endre{at}brc.hu.

Received June 30, 2009; accepted September 18, 2009; published September 23, 2009.