ANGUSTIFOLIA, a plant homolog of CtBP/BARS, functions outside the nucleus.
ABSTRACT CtBP/BARS is a unique protein family in having quite diversified cellular functions, intercellular localizations, and developmental roles. ANGUSTIFOLIA (AN) is the sole homolog of CtBP/BARS from Arabidopsis thaliana, although it has plant AN-specific motifs and a long C-terminus. Previous studies suggested that AN would function in the nucleus as a transcriptional co-repressor, as CtBPs function in animals; however, precise verification has been lacking. In this paper, we isolated a homologous gene (MAN) of AN from liverwort, Marchantia polymorpha. Transformation of the Arabidopsis an-1 mutant with 35S-driven MAN completely complemented the an-1 phenotype, although it lacks the putative nuclear localization signal (NLS) that exists in AN proteins isolated from other plant species. We constructed several plasmids for expressing modified ANs with amino acid substitutions in known motifs. The results clearly indicated that modified AN with mutations in the putative NLS-like domain could complement the an-1 phenotype. Therefore, we re-examined localization of AN using several techniques. Our results demonstrated that AN localizes on punctuate structures around the Golgi, partially overlapping with a trans-Golgi network resident, which highlighted an unexpected link between leaf development and membrane trafficking. We should reconsider the roles and evolutionary traits of AN based on these findings.
Full-textDOI: · Available from: Masataka Kajikawa, Oct 18, 2014
- SourceAvailable from: Holger Breuninger[Show abstract] [Hide abstract]
ABSTRACT: Author Summary Most of the visible growth of plant organs is driven by cell expansion without associated cell division. As plant cells are encased in cell walls, expansion requires the controlled loosening of the existing cell wall and synthesis of additional wall material. While a number of factors and plant hormones are known that promote cell expansion, what limits this process and thus restricts final cell and organ size is less well understood. Here, we identify a mutant that forms larger flowers because of increased cell expansion. The affected gene encodes a motor protein associated with the microtubule cytoskeleton that causes microtubule break-down and is required for ensuring an even distribution of secretory organelles within cells. Reduced activity of this motor protein triggers the activation of a pathway that detects defects in cell-wall integrity, which in turn leads to the observed increase in cell-wall synthesis and expansion. The Arabidopsis genome encodes another highly similar motor protein, and the combined loss of their activities causes severe defects, including reduced cell expansion. Thus, the two proteins fulfill an essential function in plant cell growth, and their full activity appears to be required to ensure normal cell-wall synthesis and a timely cessation of cell expansion.PLoS Genetics 09/2014; 10(9):e1004627. DOI:10.1371/journal.pgen.1004627 · 8.17 Impact Factor
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ABSTRACT: The highly elongated single-celled cotton fibre consists of lint and fuzz, similar to the Arabidopsis trichome. Endoreduplication is an important determinant in Arabidopsis trichome initiation and morphogenesis. Fibre development is also controlled by functional homologues of Arabidopsis trichome patterning genes, although fibre cells do not have a branched shape like trichomes. The identification and characterization of the homologues of 10 key Arabidopsis trichome branching genes in Gossypium arboreum are reported here. Nuclear ploidy of fibres was determined, and gene function in cotton callus and fibre cells was investigated. The results revealed that the nuclear DNA content was constant in fuzz, whereas a limited and reversible change occurred in lint after initiation. Gossypeum arboreum BRANCHLESS TRICHOMES (GaBLT) was not transcribed in fibres. The homologue of STICHEL (STI), which is essential for trichome branching, was a pseudogene in Gossypium. Targeted expression of GaBLT, Arabidopsis STI, and the cytokinesis-repressing GaSIAMESE in G. hirsutum fibre cells cultured in vitro resulted in branching. The findings suggest that the distinctive developmental mechanism of cotton fibres does not depend on endoreduplication. This important component may be a relic function that can be activated in fibre cells.Journal of Experimental Botany 08/2013; 64(14). DOI:10.1093/jxb/ert222 · 5.79 Impact Factor
Article: Leaf development.[Show abstract] [Hide abstract]
ABSTRACT: Leaves are the most important organs for plants. Without leaves, plants cannot capture light energy or synthesize organic compounds via photosynthesis. Without leaves, plants would be unable perceive diverse environmental conditions, particularly those relating to light quality/quantity. Without leaves, plants would not be able to flower because all floral organs are modified leaves. Arabidopsis thaliana is a good model system for analyzing mechanisms of eudicotyledonous, simple-leaf development. The first section of this review provides a brief history of studies on development in Arabidopsis leaves. This history largely coincides with a general history of advancement in understanding of the genetic mechanisms operating during simple-leaf development in angiosperms. In the second section, I outline events in Arabidopsis leaf development, with emphasis on genetic controls. Current knowledge of six important components in these developmental events is summarized in detail, followed by concluding remarks and perspectives.The Arabidopsis Book 01/2013; 11:e0163. DOI:10.1199/tab.0163