title: Protein profile of Lupinus texensis phloem sap exudates: searching for Fe- and Zn-containing proteins.
abstract: The aim of this study was to obtain a comprehensive overview of the phloem sap protein profile of Lupinus texensis, with a special focus on proteins binding Fe and Zn. L. texensis was chosen as model plant given the simplicity to obtain exudates from sieve elements. Protein profiling by 2DE revealed 249 spots, and 54 of them were unambiguously identified by MALDI-MS and ESI-MS/MS. The largest number of identified protein species belongs to protein modification/turnover and general metabolism (19-21%), followed by redox homeostasis (9%) and defense and cell structural components (7%). This protein profile is similar to that reported in other plant species, suggesting that the phloem sap proteome is quite conserved. Staining of 2DE gels for Fe-containing proteins and affinity chromatography experiments revealed the presence of two low molecular weight Fe-binding proteins in phloem sap: a metallothionein-like protein type 2B identified in the Fe-affinity chromatography, and a second protein identified with both Fe staining methods. This protein species had a molecular weight of 13.5 kDa, a pI of 5.6 and 51% homology to a phloem-specific protein from Medicago truncatula. Zinc affinity chromatography revealed four Zn-binding proteins in phloem sap, one belonging to the dehydrin family and three Zn finger proteins.
authors.affiliation: Department of Plant Nutrition, Aula Dei Experimental Station-CSIC, Zaragoza, Spain.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Lattanzio
authors.forename: Sofía
authors.initials: S
authors.lastname: Andaluz
authors.forename: Andrea
authors.initials: A
authors.lastname: Matros
authors.forename: Juan José
authors.initials: JJ
authors.lastname: Calvete
authors.forename: Julia
authors.initials: J
authors.lastname: Kehr
authors.forename: Anunciación
authors.initials: A
authors.lastname: Abadía
authors.forename: Javier
authors.initials: J
authors.lastname: Abadía
authors.forename: Ana-Flor
authors.initials: AF
authors.lastname: López-Millán
mesh_terms: D015153:Blotting, Western; D002846:Chromatography, Affinity; D015180:Electrophoresis, Gel, Two-Dimensional; D031297:Lupinus / Q000737:chemistry*; D008667:Metalloproteins / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D052585:Phloem / Q000737:chemistry*; D010940:Plant Proteins / Q000032:analysis* / Q000737:chemistry / Q000145:classification / Q000378:metabolism; D020543:Proteome / Q000032:analysis; D053719:Tandem Mass Spectrometry; D016335:Zinc Fingers
chemical_list: D008667:Metalloproteins; D010940:Plant Proteins; D020543:Proteome
keywords: Iron; Lupinus texensis; Phloem sap; Plant proteomics; Zinc