Abstract
Variegated plants are valuable materials for investigating leaf color regulated mechanisms. To unveil the role of posttranslational modification in the variegated phenotype, we conducted global quantitative phosphoproteomic analysis on different leaf color sectors of Maiyuanjinqiu and the corresponding of Catalpa fargesii using Ti4+-IMAC phosphopeptide enrichment. A total of 3778 phosphorylated sites assigned to 1646 phosphoproteins were identified, and 3221 in 1434 proteins were quantified. Differential phosphoproteins (above 1.5 or below 1/1.5) in various leaf color sectors were selected for functional enrichment analyses. Gene ontology (GO) enrichment revealed that processes of photosynthesis, regulation of the generation of precursor metabolites, response to stress, homeostasis, amino acid metabolism, transport–related processes, and most of the energy metabolisms might contribute to leaf color. KEGG pathway enrichment analysis was performed based on differential phosphoproteins (DPs) in different organelles. The result showed that most enriched pathways were located in the chloroplasts and cytosol. The phosphorylation levels of glycometabolism enzymes might greatly affect leaf variegation. Measurements of fluorescence parameters and enzyme activities confirmed that protein phosphorylation could affect plant physiology by regulating enzyme activity. These results provide new clues for further study the formation mechanisms of naturally variegated phenotype.
Highlights
Variegated leaves usually consist of green and yellow/white sectors
The values of Fv/Fm were considerably lower in the yellow sectors than in the green sectors, whereas the values were similar in the Y2 and G2 sectors (Figure 1C)
Compared with that in the green tissue, the electron transport rate of PSII (ETR(II)) was weakened in the yellow tissue, whereas the electron transport rate of PSI (ETR(I)) was enhanced under 129 μmol·m−2·s−1 in the yellow sectors (Figure 1D,E). These suggested that the energy balance of PSII and PSI was reequilibrated in the yellow sectors
Summary
Variegated species have outstanding application value in landscaping and landscape design. They are ideal materials for studying the mechanism of leaf color formation. With advances in high-throughput technology, genomics, transcriptomics, and proteomics approaches have emerged in the study of variegated leaves [1,2,3,4]. It has been reported that the yellow sectors generally had decreased photosynthesis and increased oxidative stress to the green sectors by transcriptome and proteome profiling [1,5]. We inferred that protein phosphorylation might have a great relationship with the phenotype.
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