The development of a plant leaf is a meticulously orchestrated sequence of events producing a complex organ comprising diverse cell types. The reticulate class of leaf variegation mutants displays contrasting pigmenta...The development of a plant leaf is a meticulously orchestrated sequence of events producing a complex organ comprising diverse cell types. The reticulate class of leaf variegation mutants displays contrasting pigmentation between veins and interveinal regions due to specific aberrations in the development of mesophyll cells. Thus, the reticulate mutants offer a potent tool to investigate cell-type-specific developmental processes. The discovery that most mutants are affected in plastid-localized, metabolic pathways that are strongly expressed in vasculature-associated tis- sues implicates a crucial role for the bundle sheath and their chloroplasts in proper development of the mesophyll cells. Here, we review the reticulate mutants and their phenotypic characteristics, with a focus on those in Arabidopsis thali- ana. Two alternative models have been put forward to explain the relationship between plastid metabolism and meso- phyll cell development, which we call here the supply and the signaling hypotheses. We critically assess these proposed models and discuss their implications for leaf development and bundle sheath function in C3 species. The characteriza- tion of the reticulate mutants supports the significance of plastid retrograde signaling in cell development and highlights the significance of the bundle sheath in C3 photosynthesis.展开更多
Blue native-PAGE （BN-PAGE） resolves protein complexes in their native state. When combined with immu- noblotting, it can be used to identify the presence of high molecular weight complexes at high resolution for any...Blue native-PAGE （BN-PAGE） resolves protein complexes in their native state. When combined with immu- noblotting, it can be used to identify the presence of high molecular weight complexes at high resolution for any protein, given a suitable antibody. To identify proteins in high molecular weight complexes on a large scale and to bypass the requirement for specific antibodies, we applied a tandem mass spectrometry （MS/MS） approach to BN-PAGE-resolved chloroplasts. Fractionation of the gel into six bands allowed iden- tification and label-free quantification of 1000 chloroplast proteins with native molecular weight separation. Significantly, this approach achieves a depth of identification comparable with traditional shotgun proteo- mic analyses of chloroplasts, indicating much of the known chloroplast proteome is amenable to MS/MS identification under our fractionation scheme. By limiting the number of fractionation bands to six, we facil- itate scaled-up comparative analyses, as we demonstrate with the reticulata chloroplast mutant displaying a reticulated leaf phenotype. Our comparative proteomics approach identified a candidate interacting protein of RETICULATA as well as effects on lipid remodeling proteins, amino acid metabolic enzymes, and plastid division machinery. We additionally highlight selected proteins from each sub-compartment of the chloroplast that provide novel insight on known or hypothesized protein complexes to further illus- trate the utility of this approach. Our results demonstrate the high sensitivity and reproducibility of this technique, which is anticipated to be widely adaptable to other sub-cellular compartments.展开更多
文摘The development of a plant leaf is a meticulously orchestrated sequence of events producing a complex organ comprising diverse cell types. The reticulate class of leaf variegation mutants displays contrasting pigmentation between veins and interveinal regions due to specific aberrations in the development of mesophyll cells. Thus, the reticulate mutants offer a potent tool to investigate cell-type-specific developmental processes. The discovery that most mutants are affected in plastid-localized, metabolic pathways that are strongly expressed in vasculature-associated tis- sues implicates a crucial role for the bundle sheath and their chloroplasts in proper development of the mesophyll cells. Here, we review the reticulate mutants and their phenotypic characteristics, with a focus on those in Arabidopsis thali- ana. Two alternative models have been put forward to explain the relationship between plastid metabolism and meso- phyll cell development, which we call here the supply and the signaling hypotheses. We critically assess these proposed models and discuss their implications for leaf development and bundle sheath function in C3 species. The characteriza- tion of the reticulate mutants supports the significance of plastid retrograde signaling in cell development and highlights the significance of the bundle sheath in C3 photosynthesis.
文摘Blue native-PAGE （BN-PAGE） resolves protein complexes in their native state. When combined with immu- noblotting, it can be used to identify the presence of high molecular weight complexes at high resolution for any protein, given a suitable antibody. To identify proteins in high molecular weight complexes on a large scale and to bypass the requirement for specific antibodies, we applied a tandem mass spectrometry （MS/MS） approach to BN-PAGE-resolved chloroplasts. Fractionation of the gel into six bands allowed iden- tification and label-free quantification of 1000 chloroplast proteins with native molecular weight separation. Significantly, this approach achieves a depth of identification comparable with traditional shotgun proteo- mic analyses of chloroplasts, indicating much of the known chloroplast proteome is amenable to MS/MS identification under our fractionation scheme. By limiting the number of fractionation bands to six, we facil- itate scaled-up comparative analyses, as we demonstrate with the reticulata chloroplast mutant displaying a reticulated leaf phenotype. Our comparative proteomics approach identified a candidate interacting protein of RETICULATA as well as effects on lipid remodeling proteins, amino acid metabolic enzymes, and plastid division machinery. We additionally highlight selected proteins from each sub-compartment of the chloroplast that provide novel insight on known or hypothesized protein complexes to further illus- trate the utility of this approach. Our results demonstrate the high sensitivity and reproducibility of this technique, which is anticipated to be widely adaptable to other sub-cellular compartments.
