The SNARE Protein SYP71 Expressed in Vascular Tissues Is Involved in Symbiotic Nitrogen Fixation in Lotus japonicus Nodules    

Abstract

Soluble N-Ethylmaleimide Sensitive Factor Attachment Protein Receptor (SNARE) proteins are crucial for signal transduction and development in plants. Here, we investigate a Lotus japonicus symbiotic mutant defective in one of the SNARE proteins. When in symbiosis with rhizobia, the growth of the mutant was retarded compared with that of the wild-type plant. Although the mutant formed nodules, these exhibited lower nitrogen fixation activity than the wild type. The rhizobia were able to invade nodule cells, but enlarged symbiosomes were observed in the infected cells. The causal gene, designated LjSYP71 (for L. japonicus syntaxin of plants71), was identified by map-based cloning and shown to encode a Qc-SNARE protein homologous to Arabidopsis (Arabidopsis thaliana) SYP71. LjSYP71 was expressed ubiquitously in shoot, roots, and nodules, and transcripts were detected in the vascular tissues. In the mutant, no other visible defects in plant morphology were observed. Furthermore, in the presence of combined nitrogen, the mutant plant grew almost as well as the wild type. These results suggest that the vascular tissues expressing LjSYP71 play a pivotal role in symbiotic nitrogen fixation in L. japonicus nodules.

The SNARE Protein Syp71 Is Essential for Turnip Mosaic Virus Infection by Mediating Fusion of Virus-Induced Vesicles with Chloroplasts

“…As no homozygous T-DNA insertion Arabidopsis Syp71 mutant could be isolated from the Syp71 / syp71 heterozygote, Syp71 seems essential for the development of Arabidopsis . To date no specific functions have been identified for the Syp7 subfamily except for a recent report showing that Syp71 is essential for symbiotic nitrogen fixation in Lotus japonicas nodules in a yet-unknown manner [31]. To our best knowledge, the current study represents the first to functionally characterize a SNARE family protein essential for virus infection in plants.…”

Extracellular Vesicles Isolated from the Leaf Apoplast Carry Stress-Response Proteins

“…Interestingly, SYP71 is localized mainly to the endoplasmic reticulum and is required for the infection of Arabidopsis by Turnip mosaic virus, where it plays a role in the fusion of virusinduced vesicles with chloroplasts (Wei et al, 2013). In Lotus japonicus, LjSYP71 contributes to symbiotic nitrogen fixation in nodules (Hakoyama et al, 2012).…”

The C2H2 Transcription Factor REGULATOR OF SYMBIOSOME DIFFERENTIATION Represses Transcription of the Secretory Pathway Gene VAMP721a and Promotes Symbiosome Development in Medicago truncatula

“…Reverse-genetic studies of M. truncatula have linked a few transcription factor (TF) genes to nitrogen fixation but not nodulation per se (i.e., mutants in these genes exhibit Nod + /Fix 2 phenotypes); these genes include alfalfa (Medicago sativa) Kruppel-like Zinc finger Protein2-1, Mt-Heme Activator Protein2.1 (HAP2.1), Mt-EFD, and a basic helix loop helix-TF involved in nodule vasculature development (Frugier et al, 2000;Combier et al, 2006;Vernié et al, 2008;Godiard et al, 2011). Forward genetic studies with L. japonicus have identified roles for the following proteins in the later stages of nodule and/or bacteroid development and differentiation: a sulfate transporter, Symbiotic Sulphate Transporter1; an ankyrin-repeat membrane protein, Ineffective Greenish Nodules1; homocitrate synthase, Failure in ENlargement of infected cells1; a putative iron transporter, SEN1; a syntaxin Syntaxin of plants71; and a citrate transporter, Multidrug And Toxic compound Extrusion1 Kumagai et al, 2007;Hakoyama et al, 2009Hakoyama et al, , 2012aHakoyama et al, , 2012bTakanashi et al, 2013).…”