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

Planta. 2001 Jan;212(2):279-87. doi: 10.1007/s004250000393.

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 NtXET-1 (Accession no. D86730). The expression pattern revealed highest levels of NtXET-1 mRNA in organs highly enriched in vascular tissue. The levels of NtXET-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 NtXET-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 NtXET-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 NtXET-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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Wall / metabolism*
  • DNA, Complementary
  • Glucans*
  • Glycosyltransferases / genetics
  • Glycosyltransferases / metabolism*
  • Molecular Sequence Data
  • Plants, Genetically Modified / metabolism
  • Plants, Toxic*
  • Polysaccharides / metabolism*
  • RNA, Messenger / genetics
  • Tobacco / enzymology*
  • Xylans*

Substances

  • DNA, Complementary
  • Glucans
  • Polysaccharides
  • RNA, Messenger
  • Xylans
  • xyloglucan
  • Glycosyltransferases
  • xyloglucan endotransglycosylase

Associated data

  • GENBANK/AA824986
  • GENBANK/D86730