A principal role for AtXTH18 in Arabidopsis thaliana root growth: a functional analysis using RNAi plants

Osato, Y.; Yokoyama, Ryusuke; Nishitani, Kazuhiko

doi:10.1007/s10265-006-0262-6

Cited by 104 publications

(97 citation statements)

References 56 publications

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“…Although untested at present, AtXTH31 and/or AtXTH32 may not have the capacity to access such regions. Collectively, these observations may explain why XTH-related wall phenotypes are often slight in those cases where they are observed (Cosgrove, 2000(Cosgrove, , 2005Osato et al, 2006;Miedes et al, 2011;Nishikubo et al, 2011).…”

Section: Discussionmentioning

confidence: 87%

Group III-AXTHGenes of Arabidopsis Encode Predominant Xyloglucan Endohydrolases That Are Dispensable for Normal Growth

et al. 2012

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The molecular basis of primary wall extension endures as one of the central enigmas in plant cell morphogenesis. Classical cell wall models suggest that xyloglucan endo-transglycosylase activity is the primary catalyst (together with expansins) of controlled cell wall loosening through the transient cleavage and religation of xyloglucan-cellulose cross links. The genome of Arabidopsis (Arabidopsis thaliana) contains 33 phylogenetically diverse XYLOGLUCAN ENDO-TRANSGLYCOSYLASE/ HYDROLASE (XTH) gene products, two of which were predicted to be predominant xyloglucan endohydrolases due to clustering into group III-A. Enzyme kinetic analysis of recombinant AtXTH31 confirmed this prediction and indicated that this enzyme had similar catalytic properties to the nasturtium (Tropaeolum majus) xyloglucanase1 responsible for storage xyloglucan hydrolysis during germination. Global analysis of Genevestigator data indicated that AtXTH31 and the paralogous AtXTH32 were abundantly expressed in expanding tissues. Microscopy analysis, utilizing the resorufin b-glycoside of the xyloglucan oligosaccharide XXXG as an in situ probe, indicated significant xyloglucan endohydrolase activity in specific regions of both roots and hypocotyls, in good correlation with transcriptomic data. Moreover, this hydrolytic activity was essentially completely eliminated in AtXTH31/AtXTH32 double knockout lines. However, single and double knockout lines, as well as individual overexpressing lines, of AtXTH31 and AtXTH32 did not demonstrate significant growth or developmental phenotypes. These results suggest that although xyloglucan polysaccharide hydrolysis occurs in parallel with primary wall expansion, morphological effects are subtle or may be compensated by other mechanisms. We hypothesize that there is likely to be an interplay between these xyloglucan endohydrolases and recently discovered apoplastic exo-glycosidases in the hydrolytic modification of matrix xyloglucans.

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Section: Discussionmentioning

confidence: 87%

Group III-AXTHGenes of Arabidopsis Encode Predominant Xyloglucan Endohydrolases That Are Dispensable for Normal Growth

et al. 2012

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“…6 and 7), an indicator of apoplastic lesions of Al toxicity, this reinforces the importance of XET activity changes in the expression of Al toxicity. Recently, experimental evidence supporting that a specific member of the XTH protein family plays an indispensable role in the cell elongation process has been reported (Osato et al, 2006;Liu et al, 2007).…”

Section: Discussionmentioning

confidence: 99%

Cell Wall Hemicellulose Contributes Significantly to Aluminum Adsorption and Root Growth in Arabidopsis

et al. 2011

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The cell wall (CW) has been recognized as the major target of aluminum (Al) toxicity. However, the components responsible for Al accumulation and the mechanisms of Al-induced CW function disruption are still elusive. The contribution of different CW components (pectin, hemicellulose 1 [HC1], and HC2) to adsorb Al and the effect of Al on xyloglucan endotransglucosylase/ hydrolyase activity were investigated in Arabidopsis (Arabidopsis thaliana) in this study. A fractionation procedure was optimized to effectively extract different CW components, especially to prevent the HC fraction from pectin contamination. When CW materials extracted from Al-treated roots (50 mM Al for 24 h) were fractionated, about 75% of CW Al accumulated in the HC1 fraction. A time-dependent kinetic study showed that only when the HC1 fraction was removed was the amount of Al adsorbed decreased sharply. In vivo localization of xyloglucan endotransglucosylase (XET) activity showed that Al greatly inhibited this enzyme activity within 30 min of exposure, which was concomitant with Al-induced callose deposition in roots. Results from real-time reverse transcription-polymerase chain reaction indicated that three genes may constitute the major contributors to XET activity and that the inhibition of XET activity by Al is caused by transcriptional regulation. These results, to our knowledge for the first time, demonstrate that HC is the major pool for Al accumulation. Furthermore, Al-induced reduction in XET activity could play an important role in Al-induced root growth inhibition.

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“…Accordingly, most XTHs possess either one or both of these activities (Rose et al, 2002). XTH protein activity and transcript levels have also been correlated with various aspects of plant growth and development (Redgwell and Fry, 1993;Bourquin et al, 2002;Hyodo et al, 2003;Matsui et al, 2005;Van Sandt et al, 2007a) in which cellular expansion is required, and this functionality has been confirmed using transgenic approaches (Cho et al, 2006;Osato et al, 2006). Here too, there are instances where this correlation does not hold (Pritchard et al, 1993;Palmer and Davies, 1996).…”

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confidence: 99%

The Regulation of Cell Wall Extensibility during Shade Avoidance: A Study Using Two Contrasting Ecotypes of Stellaria longipes

Sasidharan¹,

Chinnappa²,

Voesenek³

et al. 2008

Plant Physiol.

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Shade avoidance in plants involves rapid shoot elongation to grow toward the light. Cell wall-modifying mechanisms are vital regulatory points for control of these elongation responses. Two protein families involved in cell wall modification are expansins and xyloglucan endotransglucosylase/hydrolases. We used an alpine and a prairie ecotype of Stellaria longipes differing in their response to shade to study the regulation of cell wall extensibility in response to low red to far-red ratio (R/FR), an early neighbor detection signal, and dense canopy shade (green shade: low R/FR, blue, and total light intensity). Alpine plants were nonresponsive to low R/FR, while prairie plants elongated rapidly. These responses reflect adaptation to the dense vegetation of the prairie habitat, unlike the alpine plants, which almost never encounter shade. Under green shade, both ecotypes rapidly elongate, showing that alpine plants can react only to a deep shade treatment. Xyloglucan endotransglucosylase/hydrolase activity was strongly regulated by green shade and low blue light conditions but not by low R/FR. Expansin activity, expressed as acid-induced extension, correlated with growth responses to all light changes. Expansin genes cloned from the internodes of the two ecotypes showed differential regulation in response to the light manipulations. This regulation was ecotype and light signal specific and correlated with the growth responses. Our results imply that elongation responses to shade require the regulation of cell wall extensibility via the control of expansin gene expression. Ecotypic differences demonstrate how responses to environmental stimuli are differently regulated to survive a particular habitat.

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A principal role for AtXTH18 in Arabidopsis thaliana root growth: a functional analysis using RNAi plants

Cited by 104 publications

References 56 publications

Group III-AXTHGenes of Arabidopsis Encode Predominant Xyloglucan Endohydrolases That Are Dispensable for Normal Growth

Group III-AXTHGenes of Arabidopsis Encode Predominant Xyloglucan Endohydrolases That Are Dispensable for Normal Growth

Cell Wall Hemicellulose Contributes Significantly to Aluminum Adsorption and Root Growth in Arabidopsis

The Regulation of Cell Wall Extensibility during Shade Avoidance: A Study Using Two Contrasting Ecotypes of Stellaria longipes

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