title: Dioscorea alata tuber proteome analysis shows over thirty dioscorin isoforms and novel tuber proteins.
abstract: In Dioscorea, dioscorin (31 kDa) is the major storage protein constituting 85% of the total tuber proteins. An integrated proteomic and biochemical approach was used to understand the physiological role of dioscorin in the two contrasting growth stages (germinating and mature tuber). HPLC analysis showed 3 fold reduction in mannitol and 12.88 and 1.24 fold increase in sucrose and maltose in the germinating tuber. A 1.8 and 3 fold increase in sucrose phosphate synthase and mannitol dehydrogenase activity respectively was observed in the germinating tuber while a 2 fold higher invertase probably lowers the sucrose accumulation in the mature tuber. SDS-PAGE and 2-D maps of the mature and germinating tubers confirmed depletion (more than 50%) of dioscorin on germination. Dioscorin was purified using ion exchange and gel filtration chromatography with 43.32 fold purification and 38.16 yield. Out of a trail of 35 spots at 31 kDa only 12 spots (identified as dioscorin isoforms) were present in the 2D gel of the purified fraction. To search for other tuber proteins besides dioscorin, the unbound fractions of DEAE column were analysed by 2DGE. DREB 1A, caffeic acid 3-O-methyltransferase and Rab-1 small GTP binding protein were identified perhaps for the first time in the Dioscorea proteome. The interactome analysis revealed these to be involved in oxidative stress, carotenoid synthesis and vesicular transport. This is perhaps the first attempt to identify tuber proteome (although limited) and to understand the physiological significance of these proteins.
authors.affiliation: Molecular Physiology and Proteomics Laboratory, Department of Botany, University of Delhi, India.
authors.forename: Shruti
authors.initials: S
authors.lastname: Sharma
authors.affiliation: Department of Plant Bioscience, Pusan National University, Miryang, South Korea.
authors.forename: Ravi
authors.initials: R
authors.lastname: Gupta
authors.affiliation: Molecular Physiology and Proteomics Laboratory, Department of Botany, University of Delhi, India. Electronic address: rdeswal@botany.du.ac.in.
authors.forename: Renu
authors.initials: R
authors.lastname: Deswal
mesh_terms: D027742:Dioscorea / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D018525:Germination / Q000502:physiology; D009005:Monosaccharides / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D035281:Plant Tubers / Q000378:metabolism*; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D020543:Proteome / Q000032:analysis* / Q000378:metabolism; D015398:Signal Transduction; D000516:alpha-Amylases / Q000378:metabolism
chemical_list: D009005:Monosaccharides; D010940:Plant Proteins; D020033:Protein Isoforms; D020543:Proteome; C095057:dioscorin protein, Dioscorea; D000516:alpha-Amylases
keywords: Depletion; Germination; Isoforms; Storage proteins; Sugars