Achenes and receptacle tissue of Fragaria vesca, L. cultivar Yellow Wonder were shown to contain conjugated indole-3-acetic acid (IAA) that was not soluble in organic solvents and yielded IAA after strong alkaline hydrolysis, suggestive of IAA attached to plant proteins. This solvent insoluble conjugated IAA accounted for between 0.4 and 4 ng of IAA per gram fresh weight of tissue in both achenes and receptacles. To investigate this strawberry conjugate class further, a polyclonal antibody was produced to IAA-glycine attached to BSA that detected neutral indole acid esters, monocarboxylic-amino acid IAA conjugates and IAA proteins. Using immunoblotting, both achenes and receptacles of strawberry were shown to have primarily an immuno-detectable band at 76 kDa. Two-dimensional polyacrylamide gel electrophoresis yielded a wide band that was analyzed by LC-MS/MS analysis following in-gel trypsin digestion. Peptides derived from the immuno-detectable band were tentatively identified by peptide fragment analysis as being from either a chaperonin related to the hsp60 class of proteins or, alternatively, an ATP synthase. This is one of the first reports of an IAA modified protein in fruit tissue.
Bibliographical noteFunding Information:
Acknowledgements This work was supported by a grant from the National Science Foundation (IOB0111530), the Gordon and Margaret Bailey Endowment for Environmental Horticulture and by funds from the USDA Agricultural Research Service. Part of the costs of this work were oVset by the Mass Spectrometry and Proteomics Initiative of the University of Minnesota Center for Mass Spectrometry and Proteomics. ArgusLab 4.0.1 software is a freely licensed product by Mark A. Thompson (Planaria Software LLC; http://www.arguslab.com), whom we thank for making this package available.
- ATP synthase
- Auxin conjugation
- Fragaria vesca
- Heat stress protein
- IAA protein