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  • Botany & Plant Biology 2007 - Abstract Search
    quantified cell division elemental elongation and examined actin in the primary root of Arabidopsis thaliana In treatments for 48 hours that inhibit root elongation rate by 50 we find that auxins and auxin transport inhibitors can be put into two classes based on their effects on cell division elongation and actin Indoleacetic acid IAA 1 naphthalene acetic acid NAA and tri iodobenzoic acid TIBA inhibit root growth primarily through reducing the length of the growth zone rather than the maximal rate of elemental elongation and they do not reduce cell production rate These three compounds have little effect on the extent of filamentous actin as imaged in living cells or with chemical fixation and immuno cytochemistry but tend to increase actin bundling In contrast 2 4 dichlorophenoxy acetic acid 2 4 D and naphthylphthalamic acid NPA inhibit root growth primarily by reducing cell production rate These compounds remove actin slow cytoplasmic streaming yet do not lead to the mislocalization of the auxin efflux proteins PIN1 or PIN2 The effects of 2 4 D and NPA were mimicked by the actin inhibitor latrunculin B The effects of these compounds on actin were elicited with a 2 hour treatment at higher concentration

    Original URL path: http://2007.botanyconference.org/engine/search/index.php?func=detail&aid=41 (2016-02-01)
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  • Botany & Plant Biology 2007 - Abstract Search
    In a first phase of vascular differentiation defined cells are recruited within a growing organ to form continuous files the procambium In the second phase cells deriving from the procambium differentiate into xylem phloem and fibers The conducting functions of vascular tissues require perfect cell alignment and tissue continuity transverse patterning within veins as well as proper integration within the non vascular tissues The plant hormone auxin plays a primary role in procambium cell recruitment Early markers of cambium and xylem precursor cells are class III HD ZIP transcription factors They antagonize the expression of KANADI genes which are expressed in phloem precursor cells The aim of this study was to analyze direct relationships between these diverse regulatory mechanisms in vein patterning To this end we expressed KANADI1 under the control of the class III HD ZIP ATHB15 in order to reduce class III HD ZIP contents in provascular cells Ectopic expression of KAN1 in provascular cells and the shoot apical meristem inhibited the establishment of a bilateral axis during embryogenesis Furthermore seedlings developed a thicker and shortened hypocotyl had severely reduced root growth a variable number of cotyledons a reduced shoot apical meristem and no vascular system Ectopic expression

    Original URL path: http://2007.botanyconference.org/engine/search/index.php?func=detail&aid=2573 (2016-02-01)
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  • Botany & Plant Biology 2007 - Abstract Search
    elongation and microtubule organization in Chara Auxin plays important roles in multiple aspects of plant growth and development but its actions in Chara a close relative of land plants are poorly understood We tested the effets of α naphthylacetic acid NAA indole 3 acetic acid IAA and an anti auxin 4 4 4 trifluoro 3 indole 3 butyric acid TFIBA on internodal elongation and microtubule MT responses in Chara Unlike higher plants the elongation of Chara internodes did not respond to α NAA at concentrations of 10 or 0 1 µ M IAA 10 or 0 1 µ M inhibited internode elongation However the response depended on the number of internodal cells Thalli with one internodal cell were inhibited by 0 1 µM IAA and thalli with two internodal cells were inhibited by 10 µM IAA The root growth promoter TFIBA 100 µM showed no effect on internodal growth Interestingly methanol which was used as solvent for the tested compounds promoted internode elongation Rhizoid elongation and formation in Chara were not affected by IAA or TFIBA Similar to higher plants α NAA depolymerized MTs in developing antheridia in a transient and concentration dependent fashion After two h of incubation MTs

    Original URL path: http://2007.botanyconference.org/engine/search/index.php?func=detail&aid=298 (2016-02-01)
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  • Botany & Plant Biology 2007 - Abstract Search
    is null or not a SELECT 13 23 27 Abstract Detail Tropisms Pan Jianwei 1 Zhang Kuihua 2 Li Guangming 2 Chen Rujin 2 Auxin regulates polar axuin transport by regulating the auxin efflux facilitator PINs localization and activity Plant hormone auxin plays an important role in the regulation of almost all plant developmental processes such as the establishment of root and shoot architecture organ pattern formation vascular development and cell division elongation and response to the environment such as gravitropism phototropism Auxin can be polarly transported from synthesis sites to action sites in a strict directionality through influx carriers AUX1 LAX and efflux carriers PINs Recently the auxin efflux facilitator PIN proteins have been identified as rate limiting factors in the generation of local auxin gradients essential for plant development Consistent with their role in auxin transport PIN proteins are integral plasma membrane proteins exhibiting polar localization in specific plant cells However mechanisms controlling their plasma membrane localization and turnover are still unclear To understand molecular mechanisms of auxin transport involved in almost all growth and developmental processes the regulation of PINs polar localization and stability was studied using molecular genetic cellular and biochemical technologies in Arabidopsis Our primary

    Original URL path: http://2007.botanyconference.org/engine/search/index.php?func=detail&aid=1710 (2016-02-01)
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  • Botany & Plant Biology 2007 - Abstract Search
    Response Factor 9 a new player in gravity signal transduction Roberts Diana R Nadella Vijayandand Wyatt Sarah E Dept of Env Plant Biology Ohio University Athens OH 45701 Gravity is a constant stimulus involved in plant growth and development The gravity response in plants involves three basic steps signal perception signal transduction and differential growth Studies involving the gravity persistence signal gps mutants Wyatt et al 2002 have implicated the Auxin Response Factor ARF gene family in gravitropic signal transduction The goal of this research was to determine the role of ARF9 in the plant s response to gravity The expression pattern of the ARF9 transcript during the GPS treatment was studied in wild type Arabidopsis at several time points using quantitative RT PCR Interestingly expression of the ARF9 transcript was increased after the GPS treatment when compared to the cold untreated T DNA insertion mutants for ARF9 were obtained from the SALK Institute and screened for a gravity response phenotype using the GPS treatment One of the SALK lines with a T DNA insertion located in exon 12 near the C terminus of ARF9 displayed increased gravitropic curvature after the GPS treatment Semi quantitative RT PCR of the ARF9

    Original URL path: http://2007.botanyconference.org/engine/search/index.php?func=detail&aid=2705 (2016-02-01)
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  • Botany & Plant Biology 2007 - Abstract Search
    Auxin Signaling F Box 4 AFB4 is essential for hypocotyl elongation in Arabidopsis Auxin signaling involves ubiquitin mediated degradation of the Aux IAA proteins promoted by the SCF TIR1 E3 The Arabidopsis genome encodes 5 proteins that are closely related to TIR1 called AUXIN SIGNALING F BOX AFB proteins So far three of these AFB1 AFB3 have been characterized and function similarly to TIR1 A phylogenetically distinct group of F box proteins within this family is comprised of AFB4 At4g24390 and AFB5 At5g49980 To investigate the function of AFB4 in planta a mutant line has been obtained in which the AFB4 protein coding region is disrupted by T DNA insertion The afb4 mutants display a number of growth phenotypes that are more severe than any of the tir1 afb1 afb2 afb3 and afb5 mutant phenotypes Mature afb4 plants are dwarf and have a proliferation of secondary inflorescences Light grown afb4 seedlings have small tightly curled cotyledons and true leaves that display polarity defects Regardless of the light environment afb4 hypocotyls are shorter than wild type and fail to elongate when challenged with exogenous auxins or GA 3 at concentrations known to stimulate hypocotyl elongation However this apparent lack of response

    Original URL path: http://2007.botanyconference.org/engine/search/index.php?func=detail&aid=924 (2016-02-01)
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  • Botany & Plant Biology 2007 - Abstract Search
    as growth are tightly linked to GA biosynthesis by a feedback mechanism GA 20 oxidase GA20ox catalyzes a rate limiting step in the synthesis of bioactive GAs The current model for GA signaling proposes that feedback regulation functions via the activity of DELLA protein repressors where stabilization of these proteins by reduced GA levels or signaling results in the increased expression of GA20ox1 Previously we showed that AtGA20ox1 expression was up regulated in response to treatment with auxin transport inhibitors ATIs The up regulation of AtGA20ox1 caused by ATIs could be mediated by a feedback mechanism by an independent mechanism or by a combination of both We are investigating whether ATI effects on AtGA20ox1 are a consequence of feedback regulation or not Using the DR5 GUS reporter gene we showed that the auxin levels were altered following ATI treatments and RT PCR analysis showed that the expression of GA20ox1 was increased However the AtGA20ox1 up regulation caused by ATIs can be reversed by combination treatment with GA Our results suggests that the ATIs mediate their effect on AtGA20ox1 by reducing bioactive GA pools which in turn up regulates AtGA20ox1 by a feedback mechanism The effects of ATIs on GA levels

    Original URL path: http://2007.botanyconference.org/engine/search/index.php?func=detail&aid=896 (2016-02-01)
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  • Botany & Plant Biology 2007 - Abstract Search
    23 47 SQL Statement is null or not a SELECT 13 23 47 Abstract Detail Environmental Physiology Wu Hui Chen 1 Jinn Tsung Luo 2 A Versatile Calmodulin is Temperature dependent Sensor The calcium calmodulin CaM transduction pathways participated in early heat shock HS response and thermotolerance in rice Oryza sativa L seedlings was investigated HS initiates Ca 2 signal which is spatially distinct and the heat stress increased Ca 2 transients mainly from extracellular source are correlated with CaMs and OsHSP genes expression is confirmed A significant increase of Ca 2 i was observed during early HS response at 37C using Fluo 3 acetoxymethyl esters and laser scanning confocal microscopy Meanwhile exogenous application of Ca 2 and A23187 also accelerate OsCaM1 and OsHSP genes expression For turn on OsHSP genes in response to HS is depended on Ca 2 oscillations up down up down which may interpret by OsCaM1 is proposed OsCaM1 GFP mobilizes from extracellular to cytosol within 10 to 16 min with temperature dependent manner When over expression of OsCaM1 in Arabidopsis accelerate HSP genes expression during early HS response These results provide direct evidence that Ca 2 calmodulin mediated HS signaling is critical for thermotolerant acquisition

    Original URL path: http://2007.botanyconference.org/engine/search/index.php?func=detail&aid=1486 (2016-02-01)
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