Duplication of NRAMP3 gene in poplars generated two homologous transporters with distinct functions

ABSTRACT Transition metals are essential for a wealth of metabolic reactions, but their concentrations need to be tightly controlled across cells and cell compartments, as metal excess or imbalance has deleterious effects. Metal homeostasis is achieved by a combination of metal transport across membranes and metal binding to a variety of molecules. Gene duplication is a key process in evolution, as emergence of advantageous mutations on one of the copies can confer a new function. Here, we report that the poplar genome contains two paralogues encoding NRAMP3 metal transporters localized in tandem. All Populus species analyzed had two copies of NRAMP3 , whereas only one could be identified in Salix species indicating that duplication occurred when the two genera separated. Both copies are under purifying selection and encode functional transporters, as shown by expression in the yeast heterologous expression system. However, genetic complementation revealed that only one of the paralogues has retained the original function in release of metals stored in the vacuole previously characterized in A. thaliana . Confocal imaging showed that the other copy has acquired a distinct localization to the Trans Golgi Network (TGN). Expression in poplar indicated that the copy of NRAMP3 localized on the TGN has a novel function in the control of cell-to-cell transport of manganese. This work provides a clear case of neo-functionalization through change in the subcellular localization of a metal transporter as well as evidence for the involvement of the secretory pathway in cell-to-cell transport of manganese

AUXIN BINDING PROTEIN1 links cell wall remodelling, auxin signalling and cell expansion in Arabidopsis

[EN] Cell expansion is an increase in cell size and thus plays an essential role in plant growth and development. Phytohormones and the primary plant cell wall play major roles in the complex process of cell expansion. In shoot tissues, cell expansion requires the auxin receptor AUXIN BINDING PROTEIN1 (ABP1), but the mechanism by which ABP1 affects expansion remains unknown. We analyzed the effect of functional inactivation of ABP1 on transcriptomic changes in dark-grown hypocotyls and investigated the consequences of gene expression on cell wall composition and cell expansion. Molecular and genetic evidence indicates that ABP1 affects the expression of a broad range of cell wall-related genes, especially cell wall remodeling genes, mainly via an SCFTIR/AFB-dependent pathway. ABP1 also functions in the modulation of hemicellulose xyloglucan structure. Furthermore, fucosidase-mediated defucosylation of xyloglucan, but not biosynthesis of nonfucosylated xyloglucan, rescued dark-grown hypocotyl lengthening of ABP1 knockdown seedlings. In muro remodeling of xyloglucan side chains via an ABP1-dependent pathway appears to be of critical importance for temporal and spatial control of cell expansion.We thank Markus Pauly (University of California, Berkeley) for kindly providing the seeds of AXY8 overexpressor, Mark Estelle (University of California, San Diego, Howard Hughes Medical Institute) for seeds of the triple tir afb2 afb3 mutant, Xing Wang Deng (Yale University) for seeds of cop10-4, Doan Luu (CNRS, Montpellier) for seeds of the 35S: PIP2; 1-GFP line, and Jiri Friml (Institute of Science and Technology, Vienna) for seeds of the abp1-5 mutant. We thank Sylvie Citerne from the Plant Observatory at Institut Jean-Pierre Bourgin (INRA) for cell wall composition analysis. This work has benefitted from the facilities and expertise of the Imagif Cell Biology Unit of the Gif campus, which is supported by the Conseil General de l'Essonne, France. We also thank Jessica Marion for technical assistance in electron microscopy. This work was supported by the ANR blanc AuxiWall Project ANR-11-BSV5-0007. C.P.-R.'s team is also funded by the CNRS and G.M. by INRA. Work in the laboratories of D.A. and M.A.B. was supported by grants from the Spanish Ministry of Science and Innovation (BIO2010-15071 and CSD2007-00057) and the Generalitat Valenciana (ACOMP/2011/288 and PROMETEO/2010/020). We thank Philip Harris (University of Auckland) and Spencer Brown (Institut des Sciences du Vegetal, CNRS) for critical reading of the article and useful comments.Parque, S.; Mouille, G.; Grandont, L.; Alabadí Diego, D.; Gaertner, C.; Goyallon, A.; Muller, P.... (2014). AUXIN BINDING PROTEIN1 links cell wall remodelling, auxin signalling and cell expansion in Arabidopsis. Plant Cell. 26(1):280-291. https://doi.org/10.1105/tpc.113.120048S28029126

Insertion mutagenesis in <em>Medicago truncatula</em>. The grain legume (FP6-GLIP) Tnt1 project

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