Expression of XET‐related genes and its relation to elongation in leaves of barley (Hordeum vulgare L.)

• Published in: Plant, cell and environment cell and environment, 1997-12, Vol.20 (12), p.1439-1450
• Main Authors: SCHÜNMANN, P. H. D., SMITH, R. C., LÅNG, V., MATTHEWS, P. R., CHANDLER, P. M.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; cDNA; Economic plant physiology; Fundamental and applied biological sciences. Psychology; gene expression; gibberellin (GA); Growth and development; Hordeum vulgare; leaf elongation; Metabolism; Morphogenesis, differentiation, rhizogenesis, tuberization. Senescence; Photosynthesis, respiration. Anabolism, catabolism; Plant physiology and development; relative elemental growth rate (REGR); xyloglucan endotransglycosylase (XET)
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1046/j.1365-3040.1997.d01-49.x

ABSTRACT Five cDNA clones were isolated from barley (Hordeum vulgare L.) that encoded mRNAs related to xyloglucan endotransglycosylase (XET). One of the clones encoded a protein with XET activity in vitro. Sequence comparisons 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 were represented once, or possibly twice, in the barley genome. Treatment of dwarf mutants with gibberellic acid (GA3), or homozygosity at the ‘slender’ (sln1) locus, resulted in a 2.5‐fold (approximately) stimulation of blade elongation rate. Three of the five clones detected mRNAs that were maximally expressed towards the base of the blade, and present in greater quantities in GA3‐treated or slender seedlings. The remaining two clones detected mRNAs that were maximally expressed in the middle of the blade. Relative elemental growth rate (REGR) profiles of leaves growing with or without GA3 treatment revealed similar maximal REGR values despite a 2.5‐fold difference in leaf elongation rate. Segments of GA3‐treated leaves attained their maximal REGR values 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 GA3‐treated seedlings a second activity peak was observed near the distal end of the elongation zone. We conclude that there are likely to be several XET isoenzymes with different expression patterns, and identify those XET‐related proteins potentially involved in leaf elongation.