Proteomic analysis of the soybean symbiosome identifies new symbiotic proteins.
Legumes form a symbiosis with rhizobia in which the plant provides an energy source to the rhizobia bacteria that it uses to fix atmospheric nitrogen. This nitrogen is provided to the legume plant, allowing it to grow without the addition of nitrogen fertilizer. As part of the symbiosis, the bacteria in the infected cells of a new root organ, the nodule, are surrounded by a plant-derived membrane, the symbiosome membrane, which becomes the interface between the symbionts. Fractions containing the symbiosome membrane (SM) and material from the lumen of the symbiosome (peribacteroid space or PBS) were isolated from soybean root nodules and analyzed using nongel proteomic techniques. Bicarbonate stripping and chloroform-methanol extraction of isolated SM were used to reduce complexity of the samples and enrich for hydrophobic integral membrane proteins. One hundred and ninety-seven proteins were identified as components of the SM, with an additional fifteen proteins identified from peripheral membrane and PBS protein fractions. Proteins involved in a range of cellular processes such as metabolism, protein folding and degradation, membrane trafficking, and solute transport were identified. These included a number of proteins previously localized to the SM, such as aquaglyceroporin nodulin 26, sulfate transporters, remorin, and Rab7 homologs. Among the proteome were a number of putative transporters for compounds such as sulfate, calcium, hydrogen ions, peptide/dicarboxylate, and nitrate, as well as transporters for which the substrate is not easy to predict. Analysis of the promoter activity for six genes encoding putative SM proteins showed nodule specific expression, with five showing expression only in infected cells. Localization of two proteins was confirmed using GFP-fusion experiments. The data have been deposited to the ProteomeXchange with identifier PXD001132. This proteome will provide a rich resource for the study of the legume-rhizobium symbiosis.
From the ‡University of Sydney, School of Biological Sciences, Sydney Australia;
Victoria C
VC
Clarke
From the ‡University of Sydney, School of Biological Sciences, Sydney Australia;
Patrick C
PC
Loughlin
From the ‡University of Sydney, School of Biological Sciences, Sydney Australia;
Aleksandr
A
Gavrin
From the ‡University of Sydney, School of Biological Sciences, Sydney Australia;
Chi
C
Chen
From the ‡University of Sydney, School of Biological Sciences, Sydney Australia;
Ella M
EM
Brear
From the ‡University of Sydney, School of Biological Sciences, Sydney Australia; §Flinders University, School of Biological Sciences, Adelaide Australia.
David A
DA
Day
From the ‡University of Sydney, School of Biological Sciences, Sydney Australia; penny.smith@sydney.edu.au.
Penelope M C
PM
Smith
D000595:Amino Acid Sequence; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D059625:Liquid-Liquid Extraction; D008565:Membrane Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D053858:Metabolic Networks and Pathways / Q000235:genetics; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D059828:Plant Cells / Q000737:chemistry / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D020543:Proteome / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D012231:Rhizobium / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D053204:Root Nodules, Plant / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013025:Glycine max / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013559:Symbiosis / Q000502:physiology; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D000090802:rab7 GTP-Binding Proteins
D002352:Carrier Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D010750:Phosphoproteins; D010940:Plant Proteins; D020543:Proteome; C045625:nodulin; D000090802:rab7 GTP-Binding Proteins; C103794:remorin; D020691:rab GTP-Binding Proteins