Phd. Schunmann et al., EXPRESSION OF XET-RELATED GENES AND ITS RELATION TO ELONGATION IN LEAVES OF BARLEY (HORDEUM-VULGARE L.), Plant, cell and environment, 20(12), 1997, pp. 1439-1450
Five cDNA clones were isolated from barley (Hordeum vulgare L.) that e
ncoded mRNAs related to xyloglucan endotransglycosylase (XET), One of
the clones encoded a protein with XET activity in vitro. Sequence comp
arisons revealed five families of XET-related sequences, one of which
(containing two of the barley genes) was novel, Hybridization studies
using clone-specific probes indicated that the corresponding genes wer
e represented once, or possibly twice, in the barley genome, Treatment
of dwarf mutants with gibberellic acid (GA(3)), or homozygosity at th
e 'slender' (sln1) locus, resulted in a 2.5-fold (approximately) stimu
lation of blade elongation rate, Three of the five clones detected mRN
As that were: maximally expressed towards the base of the blade, and p
resent in greater quantities in GA(3)-treated or slender seedlings, Th
e remaining two clones detected mRNAs that were maximally expressed in
the middle of the blade, Relative elemental growth rate (REGR) profil
es of leaves growing with or without GA(3) treatment revealed similar
maximal REGR values despite a 2.5-fold difference in leaf elongation r
ate, Segments of GA(3)-treated leaves attained their maximal REGR valu
es more rapidly, this being associated with enhanced expression of the
three 'basal' XET-related mRNAs, Highest XET activities were detected
in the base of the elongation zone, and in GA(3)-treated seedlings a
second activity peak was observed near the distal end of the elongatio
n zone, We conclude that there are likely to be several XET isoenzymes
with different expression patterns, and identify those XFT-related pr
oteins potentially involved in leaf elongation.