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Phosphoproteomic analysis of chromoplasts from sweet orange during fruit ripening
Author(s) -
Zeng Yunliu,
Pan Zhiyong,
Wang Lun,
Ding Yuduan,
Xu Qiang,
Xiao Shunyuan,
Deng Xiuxin
Publication year - 2014
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/ppl.12080
Subject(s) - chromoplast , plastid , citrus × sinensis , phosphorylation , biochemistry , biology , phosphoprotein , protein phosphorylation , ripening , proteome , chloroplast , orange (colour) , botany , protein kinase a , food science , gene
Like other types of plastids, chromoplasts have essential biosynthetic and metabolic activities which may be regulated via post‐translational modifications, such as phosphorylation, of their resident proteins. We here report a proteome‐wide mapping of in vivo phosphorylation sites in chromoplast‐enriched samples prepared from sweet orange [ Citrus sinensis (L.) Osbeck] at different ripening stages by titanium dioxide‐based affinity chromatography for phosphoprotein enrichment with LC‐MS / MS . A total of 109 plastid‐localized phosphoprotein candidates were identified that correspond to 179 unique phosphorylation sites in 135 phosphopeptides. On the basis of Motif‐X analysis, two distinct types of phosphorylation sites, one as proline‐directed phosphorylation motif and the other as casein kinase II motif, can be generalized from these identified phosphopeptides. While most identified phosphoproteins show high homology to those already identified in plastids, approximately 22% of them are novel based on BLAST search using the public databases PhosPhAt and P 3 DB . A close comparative analysis showed that approximately 50% of the phosphoproteins identified in citrus chromoplasts find obvious counterparts in the chloroplast phosphoproteome, suggesting a rather high‐level of conservation in basic metabolic activities in these two types of plastids. Not surprisingly, the phosphoproteome of citrus chromoplasts is also characterized by the lack of phosphoproteins involved in photosynthesis and by the presence of more phosphoproteins implicated in stress/redox responses. This study presents the first comprehensive phosphoproteomic analysis of chromoplasts and may help to understand how phosphorylation regulates differentiation of citrus chromoplasts during fruit ripening.