Journal Article

Protein and metabolite composition of xylem sap from field-grown soybeans (Glycine max)

Krishnan, Hari B., Bennett, John O., Sicher, Richard C., Natarajan, Savithiry S.

2011

Overview

The xylem, in addition to transporting water, nutrients and metabolites, is also involved in long-distance signaling in response to pathogens, symbionts and environmental stresses. Xylem sap has been shown to contain a number of proteins including metabolic enzymes, stress-related proteins, signal transduction proteins and putative transcription factors. Previous studies on xylem sap have mostly utilized plants grown in controlled environmental chambers. However, plants in the field are subjected to high light and to environmental stress that is not normally found in growth chambers. In this study, we have examined the protein and metabolite composition of xylem sap from field-grown cultivated soybean plants. One-dimensional gel electrophoresis of xylem sap from determinate, indeterminate, nodulating and non-nodulating soybean cultivars revealed similar protein profiles consisting of about 8-10 prominent polypeptides. Two-dimensional gel electrophoresis of soybean xylem sap resulted in the visualization of about 60 distinct protein spots. A total of 38 protein spots were identified using MALDI-TOF MS and LC-MS/MS. The most abundant proteins present in the xylem sap were identified as 31 and 28 kDa vegetative storage proteins. In addition, several proteins that are conserved among different plant species were also identified. Diurnal changes in the metabolite profile of xylem sap collected during a 24-h cycle revealed that asparagine and aspartate were the two predominant amino acids irrespective of the time collected. Pinitol (d-3-O-methyl-chiro-inositol) was the most abundant carbohydrate present. The possible roles of xylem sap proteins and metabolites as nutrient reserves for sink tissue and as an indicator of biotic stress are also discussed.

• Publisher: Berlin/Heidelberg : Springer-Verlag,Springer,Springer Berlin Heidelberg,Springer Nature B.V
• Subject: abiotic stress / Agriculture / Amino acids / Amino Acids - analysis / analysis / asparagine / aspartic acid / Biological and medical sciences / Biomedical and Life Sciences / biotic stress / Carbohydrates / Carbohydrates - analysis / chemistry / Circadian Rhythm / Circadian Rhythm - physiology / Cultivars / diurnal variation / Ecology / Electrophoresis / Electrophoresis, Gel, Two-Dimensional / Electrophoresis, Gel, Two-Dimensional - methods / Environmental stress / enzymes / field crops / Forestry / Fundamental and applied biological sciences. Psychology / Gels / Genetic Variation / genetics / Glycine max / Glycine max - chemistry / Glycine max - genetics / Glycine max - metabolism / Growth chambers / heat shock proteins / Life Sciences / metabolism / Metabolites / methods / Molecular weight / nodulation / Nutrient reserves / nutrients / Original Article / pathogens / physiology / pinitol / Plant Exudates / Plant Exudates - chemistry / plant physiology / Plant Proteins / Plant Proteins - analysis / Plant Sciences / Plant species / Plants / polypeptides / Protein metabolism / Proteins / Proteomics / Proteomics - methods / sap / Seedlings / signal transduction / Soybeans / Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Storage proteins / Tandem Mass Spectrometry / transcription (genetics) / transcription factors / two-dimensional gel electrophoresis / vegetative growth / Xylem / Xylem - chemistry