Isotope Labeling-Based Quantitative Proteomics of Developing Seeds of Castor Oil Seed (<i>Ricinus communis</i> L.)

In
this study, we used a mass spectrometry-based quantification
approach employing isotopic (ICPL) and isobaric (iTRAQ) labeling to
investigate the pattern of protein deposition during castor oil seed
(Ricinus communis L.) development, including that
of proteins involved in fatty acid metabolism, seed-storage proteins
(SSPs), toxins, and allergens. Additionally, we have used off-line
hydrophilic interaction chromatography (HILIC) as a step of peptide
fractionation preceding the reverse-phase nanoLC coupled to a LTQ
Orbitrap. We were able to identify a total of 1875 proteins, and from
these 1748 could be mapped to extant castor gene models, considerably
expanding the number of proteins so far identified from developing
castor seeds. Cluster validation and statistical analysis resulted
in 975 protein trend patterns and the relative abundance of 618 proteins.
The results presented in this work give important insights into certain
aspects of the biology of castor oil seed development such as carbon
flow, anabolism, and catabolism of fatty acid and the pattern of deposition
of SSPs, toxins, and allergens such as ricin and 2S albumins. We also
found, for the first time, some genes of SSP that are differentially
expressed during seed development.