Membrane traffic and organelle integrity in the plant secretory pathway depend on ARF-GTPases, which are activated by guanine-nucleotide exchange factors （ARF-GEFs）. While maintenance of conserved roles, evolution o...Membrane traffic and organelle integrity in the plant secretory pathway depend on ARF-GTPases, which are activated by guanine-nucleotide exchange factors （ARF-GEFs）. While maintenance of conserved roles, evolution of unique functions as well as tissue-specific roles have been shown for a handful of plant ARF-GEFs, a fundamental yet unanswered question concerns the extent to which their function overlaps during cell growth. To address this, we have characterized pao, a novel allele of GNOM-like 1 （GNL1）, a brefeldin A （BFA）-insensitive ARF-GEF, isolated through a confocal microscopy-based forward genetics screen of the Golgi in Arabidopsis thaliana. Specifically, we have analyzed the dependence of the integrity of trafficking routes and secretory organelles on GNL1 availability during expansion stages of cotyledon epidermal cells, an exquisite model system for vegetative cell growth analyses in intact tissues. We show that Golgi traffic is influenced largely by GNL1 availability at early stages of cotyledon cell expansion but by BFA- sensitive GEFs when cell growth terminates. These data reveal an unanticipated level of complexity in the biology of GNL1 by showing that its cellular roles are correlated with cell growth. These results also indicate that the cell growth stage is an important element weighting into functional analyses of the cellular roles of ARF-GEFs.展开更多
Plant cell walls are complex structures that offer structural and mechanical support to plant cells and are ultimately responsible for plant architecture and form. Pectins are a large group of complex polysaccharides ...Plant cell walls are complex structures that offer structural and mechanical support to plant cells and are ultimately responsible for plant architecture and form. Pectins are a large group of complex polysaccharides of the plant cell wall that are made in the Golgi and secreted to the wall. The methylesterification of pectins is believed to be an important factor for the dynamic properties of the cell wall. Here, we report on a protein of unknown function discovered using an extensive proteomics analysis of cotton Golgi. Through bioinformatic analyses, we identified the ortholog of such protein, here named cotton Golgi-related 3 （CGR3） in Arabidopsis and found that it shares conserved residues with S- adenosylmethionine methyltransferases. We established that CGR3 is localized at the Golgi apparatus and that the expression of the CGR3 gene is correlated with that of several cell wall biosynthetic genes, suggesting a possible role of the protein in pectin modifications. Consistent with this hypothesis, immunofluorescence microscopy with antibodies for homogalacturonan pectins （HG） indicated that the celt wails of cgr3 knockout mutants and plants overexpressing CGR3 are decreased and increased in HG methylesterification, respectively. Our results suggest that CGR3 plays a role in the methylesterification of homogalacturonan in Arabidopsis.展开更多
基金We acknowledge support by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, US Department of Energy （award number DE-FG02-91ER20021） and National Science Foundation （MCB 0948584） （F.B.）.We thank Eileen Morey for editing the manuscript. We thank Dr Sang Jin Kim, Dr Luciana Renna, and Ya Shiuan Lai for technical assistance. We are grateful to Prof. A. Nebenf0hr （University of Tennessee） for the gift of the ER-YK seeds, Prof. Ikuko Hara-Nishimura for the ermo 1-2 line, and Dr Sandra Rich and Prof. Gerd Jurgens for the GNLIIGNLI-YFP line. W.D. and F.B. designed the research W.D., K.T., and G.S. performed research+1 种基金 W.D. and F.B. analyzed data F.B. wrote the paper. No conflict of interest declared.
文摘Membrane traffic and organelle integrity in the plant secretory pathway depend on ARF-GTPases, which are activated by guanine-nucleotide exchange factors （ARF-GEFs）. While maintenance of conserved roles, evolution of unique functions as well as tissue-specific roles have been shown for a handful of plant ARF-GEFs, a fundamental yet unanswered question concerns the extent to which their function overlaps during cell growth. To address this, we have characterized pao, a novel allele of GNOM-like 1 （GNL1）, a brefeldin A （BFA）-insensitive ARF-GEF, isolated through a confocal microscopy-based forward genetics screen of the Golgi in Arabidopsis thaliana. Specifically, we have analyzed the dependence of the integrity of trafficking routes and secretory organelles on GNL1 availability during expansion stages of cotyledon epidermal cells, an exquisite model system for vegetative cell growth analyses in intact tissues. We show that Golgi traffic is influenced largely by GNL1 availability at early stages of cotyledon cell expansion but by BFA- sensitive GEFs when cell growth terminates. These data reveal an unanticipated level of complexity in the biology of GNL1 by showing that its cellular roles are correlated with cell growth. These results also indicate that the cell growth stage is an important element weighting into functional analyses of the cellular roles of ARF-GEFs.
文摘Plant cell walls are complex structures that offer structural and mechanical support to plant cells and are ultimately responsible for plant architecture and form. Pectins are a large group of complex polysaccharides of the plant cell wall that are made in the Golgi and secreted to the wall. The methylesterification of pectins is believed to be an important factor for the dynamic properties of the cell wall. Here, we report on a protein of unknown function discovered using an extensive proteomics analysis of cotton Golgi. Through bioinformatic analyses, we identified the ortholog of such protein, here named cotton Golgi-related 3 （CGR3） in Arabidopsis and found that it shares conserved residues with S- adenosylmethionine methyltransferases. We established that CGR3 is localized at the Golgi apparatus and that the expression of the CGR3 gene is correlated with that of several cell wall biosynthetic genes, suggesting a possible role of the protein in pectin modifications. Consistent with this hypothesis, immunofluorescence microscopy with antibodies for homogalacturonan pectins （HG） indicated that the celt wails of cgr3 knockout mutants and plants overexpressing CGR3 are decreased and increased in HG methylesterification, respectively. Our results suggest that CGR3 plays a role in the methylesterification of homogalacturonan in Arabidopsis.
