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Disruptions in AUXl-Dependent Auxin Influx Alter Hypocotyl Phototropism in Arabidopsis

Molecular Plant 2008年第1期1卷 129-144页

作者： Bethany B. Stonea Emily L. Stowe-Evans Reneé M. Harper R. Brandon Celaya karin ljung Goran Sandbergc Emmanuel Liscum Division of Biological Sciences University of Missouri Columbia Missouri 65211 USA Christopher S. Bond Life Sciences Center University of Missouri Columbia Missouri 65211 USA Department of Forest Genetics and Plant Physiology Umea Plant Science Center SE-90183 Umea Sweden Current address: Biology Department Bucknell University Lewisburg Pennsylvania 17837 USA.

Phototropism represents a differential growth response by which plant organs can respond adaptively to changes in the direction of incident light to optimize leaf/stem positioning for photosynthetic light capture and root growth orientation for water/nutrient acquisition. Studies over the past few years have identified a number of compo- nents in the signaling pathway（s） leading to development of phototropic curvatures in hypocotyls. These include the pho- totropin photoreceptors （photl and phot2） that perceive directional blue-light （BL） cues and then stimulate signaling, leading to relocalization of the plant hormone auxin, as well as the auxin response factor NPH4/ARF7 that responds to changes in local auxin concentrations to directly mediate expression of genes likely encoding proteins necessary for development of phototropic curvatures, While null mutations in NPH4/ARF7 condition an aphototropic response to unidirectional BL, seedlings carrying the same mutations recover BL-dependent phototropic responsiveness if coirradiated with red light （RL） or pre-treated with either ethylene. In the present study, we identify second-site enhancer mutations in the nph4 background that abrogate these recovery responses. One of these mutations-mapl （modifier of arf7 phenotypes 1）-was found to represent a missense allele of AUX1-a gene encoding a high-affinity auxin influx carrier previously associated with a number of root responses. Pharmocological studies and analyses of additional auxl mutants confirmed that AUX1 functions as a modulator of hypocotyl phototropism. Moreover, we have found that the strength of dependence of hypocotyl phototropism on AUX1-mediated auxin influx is directly related to the auxin responsiveness of the seedling in question.

关键词： AUX1-Dependent Auxin NPH4/ARF7

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Hormonal control of the shoot stem-cell niche

Hormonal control of the shoot stem-cell niche

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从植物科学到农业发展——2012全国植物生物学大会

作者： Stig U.Andersen karin ljung Karel Dolezal Andrej Miotk Sebastian J.Schultheiss Jan U.Lohmann Max Planck Institute for Developmental Biology Department of Forest Genetics and Plant Physiology Umea Plant Science CentreSwedish University of Agricultural Sciences Laboratory of Growth Regulators Palacky University and Institute of Experimental Botany Academy of Sciences of the Czech Republic Department of Stem Cell Biology University of Heidelberg

The classic phytohormonescytokinin and auxin play essential roles in the maintenance of stem-cell systems embedded in shoot and root meristems,and exhibit complex functional *** we show that the activity of both hormones directly converges on the promoters of two A-type ARABIDOPSIS RESPONSE REGULATOR(ARR) genes,ARR7 and ARR15,which are negative regulators of cytokininsignalling and have important meristematic *** ARR7 and ARR15 expression in the shoot apical meristem (SAM) is induced by cytokinin,auxin has a negative effect,which is,at least in part, mediated by the AUXIN RESPONSE FACTOR5/MONOPTEROS(MP) transcription factor. Our results provide a mechanistic framework for hormonal control of the apical stem-cell niche and demonstrate how root and shoot stem-cell systems differ in their response to phytohormones.

关键词： stem-cell niche ARRs MONOPTEROS phytohormones cross talk.

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