Plant & Animal Genomes XVII Conference

January 10-14, 2009
Town & Country Convention Center
San Diego, CA

Label-Free Relative Quantitation Of Developmentally Expressed Soluble And Membrane-Bound Proteins In Developing Fruit Juice Sac Cells Of Citrus sinensis

Ehud Katz¹ , Mario G Fon¹ , Rich Eigenheer² , Brett S Phinney² , Avi Sadka³ , Eduardo Blumwald¹

¹  Dept of Plant Sciences, University of California, Davis, CA95616, USA

²  Proteomics Core Facility, Genome Center, University of California, Davis CA95616, USA;

³  Dept of Fruit Tree Sciences; Volcani Center, ARO, Israel.

The pathways involved in the processes associated with fruit development and ripening are unique to plants and vary between species. Developmental, physiological, anatomical, biochemical and structural differences contribute to the operation of unique pathways, genes and proteins. Our initial efforts towards the characterization of the Washington navel fruit proteome identified 1,400 juice sac cell-specific proteins and enzymes [Planta(2007), 226:989-1005] . This effort facilitated the identification of a large number of biosynthetic pathways that are associated with fruit development and fruit quality traits. Following these efforts, we have now developed a label-free method for the identification of proteins and the quantification of changes among different samples. Accurate LC-MS/MS data were acquired with a Finnigan LTQ-FT for the differentially expressed proteins in the three developmental stages, then label-free techniques were employed to quantify differences between proteins of the three subsets: Both label-free spectral counting and comparison of peak intensities using the Sieve program were used. Statistical analyses were conducted with Spotfire software. A citrus genome-wide ESTs database and the NCBI-nr (green plants) database were used to identify proteins, which were subsequently classified according to their putative and assigned functions to known biosynthetic pathways. A number of proteins were found to differ between the three developmental stages of orange fruits, indicating significant shifts in some pathways that suggest mechanisms for the metabolic changes affecting the quality of the fruit. Among these; sugar ion homeostasis, amino acid synthesis and, hormonal balance, citrate metabolism, etc. will be presented and discussed.