Proteome analysis of plastids from developing seeds of Jatropha curcas L.

In this study, we performed a proteomic analysis of plastids isolated from the endosperm of developing Jatropha curcas seeds that were in the initial stage of deposition of protein and lipid reserves. Proteins extracted from the plastids were digested with trypsin, and the peptides were applied to an EASY-nano LC system coupled inline to an ESI-LTQ-Orbitrap Velos mass spectrometer, and this led to the identification of 1103 proteins representing 804 protein groups, of which 923 proteins were considered as true identifications, and this considerably expands the repertoire of J. curcas proteins identified so far. Of the identified proteins, only five are encoded in the plastid genome, and none of them are involved in photosynthesis, evidentiating the nonphotosynthetic nature of the isolated plastids. Homologues for 824 out of 923 identified proteins were present in PPDB, SUBA, or PlProt databases while homologues for 13 proteins were not found in any of the three plastid proteins databases but were marked as plastidial by at least one of the three prediction programs used. Functional classification showed that proteins belonging to amino acids metabolism comprise the main functional class, followed by carbohydrate, energy, and lipid metabolisms. The small and large subunits of Rubisco were identified, and their presence in the plastids is considered to be an adaptive feature counterbalancing for the loss of one-third of the carbon as CO2 as a result of the conversion of carbohydrate to oil through glycolysis. While several enzymes involved in the biosynthesis of several precursors of diterpenoids were identified, we were unable to identify any terpene synthase/cyclase, which suggests that the plastids isolated from the endosperm of developing seeds do not synthesize phorbol esters. In conclusion, our study provides insights into the major biosynthetic pathways and certain unique features of the plastids from the endosperm of developing seeds at the whole proteome level.

Deep proteome analysis of gerontoplasts from the inner integument of developing seeds of Jatropha curcas.

UNLABELLED: The inner integument of Jatropha curcas seeds is a non-photosynthetic tissue that acts primarily as a conduit for the delivery of nutrients to the embryo and endosperm. In this study we performed a histological and transmission electron microscopy analysis of the inner integument in stages prior to fertilization to 25days after pollination, to establish the structural changes associated with the plastid to gerontoplast transition. This study showed that plastids are subjected to progressive changes, which include the dismantling of the internal membrane system, matrix degradation and the formation of stromule-derived vesicles. A proteome analysis of gerontoplasts isolated from the inner integument at 25days after pollination, resulted in the identification of 1923 proteins, which were involved in a myriad of metabolic functions, such as synthesis of amino acids and fatty acids. Among the identified proteins, were also a number of hydrolases (peptidases, lipases and carbohydrases), which presumably are involved in the ordered dismantling of this organelle to provide additional sources of nutrients for the growing embryo and endosperm. The dataset we provide here may provide a foundation for the study of the proteome changes associated with the plastid to gerontoplast transition in non-photosynthetic tissues. SIGNIFICANCE: We describe ultrastructural features of gerontoplasts isolated from the inner integument of developing seeds of Jatropha curcas, together with a deep proteome analysis of these gerontoplasts. This article explores a new aspect of the biology of plastids, namely the ultrastructural and proteome changes associated with the transition plastid to gerontoplast in a non-photosynthetic tissue.