Functional characterisation of Nicotiana tabacum xyloglucan endotransglycosylase (NtXET-1): generation of transgenic tobacco plants and changes in cell wall xyloglucan (original) (raw)

Abstract.

To study the function of xyloglucan endotransglycosylase (XET) in vivo we isolated, a tomato (Lycopersicon esculentum Mill.) XET cDNA (GenBank AA824986) from the homologous tobacco (Nicotiana tabacum L.) clone named _Nt_XET-1 (Accession no. D86730). The expression pattern revealed highest levels of _Nt_XET-1 mRNA in organs highly enriched in vascular tissue. The levels of _Nt_XET-1 mRNA decreased in midribs with increasing age of leaves. Increasing leaf age was correlated with an increase in the average molecular weight (MW) of xyloglucan (XG) and a decrease in the relative growth rates of leaves. Transgenic tobacco plants with reduced levels of XET activity were created to further study the biochemical consequences of reduced levels of _Nt_XET-1 expression. In two independent lines, total XET activity could be reduced by 56% and 37%, respectively, in midribs of tobacco plants transformed with an antisense construct. The decreased activity led to an increase in the average MW of XG by at least 20%. These two lines of evidence argue for _Nt_XET-1 being involved in the incorporation of small XG molecules into the cell wall by transglycosylation. Reducing the incorporation of small XG molecules will result in a shift towards a higher average MW. The observed reduction in _Nt_XET-1 expression and increase in the MW of XG in older leaves might be associated with strengthening of cell walls by reduced turnover and hydrolysis of XG.

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Authors and Affiliations

  1. U.D. Fisiología Vegetal, Facultad de Ciencias Biológicas, Univ. de Valencia, Dr. Moliner 50, Burjassot, 46100 Valencia, Spain, , , , , , ES
    Ester P. Lorences & Coral Barrachina
  2. Institut für Pflanzengenetik und Kulturpflanzenforschung, Corrensstr. 3, 06466 Gatersleben, Germany, , , , , , DE
    Karin Herbers & Uwe Sonnewald

Authors

  1. Karin Herbers
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  2. Ester P. Lorences
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  3. Coral Barrachina
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  4. Uwe Sonnewald
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Received: 24 January 2000 / Accepted: 21 July 2000

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Herbers, K., Lorences, E., Barrachina, C. et al. Functional characterisation of Nicotiana tabacum xyloglucan endotransglycosylase (_Nt_XET-1): generation of transgenic tobacco plants and changes in cell wall xyloglucan.Planta 212, 279–287 (2001). https://doi.org/10.1007/s004250000393

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