Abstract
We have isolated loss of function mutant of TRG1/XYL1 gene which encodes a cell wall hydrolyzing enzyme, α-xylosidase, as one of the high temperature resistant germination mutants of Arabidopsis. Over-expression of TRG1/XYL1 inhibited germination of the seeds at 28 oC, indicating that the gene has suppressive role on germination at supra-optimal temperature conditions. α-xylosidase removes xylose residue from the non-reducing end of xyloglucan oligosaccharides (XGOs), and it has been suggested to be a key step of further degradation of the oligosaccharides. HPLC and MALDI/TOFMS analyses revealed the over-accumulation of XGO molecules in developing fruits, leaves and seeds of trg1/xyl1 mutant. In addition to the germination phenotype, trg1/xyl1 had small flower organs, short and fat siliques, and the cells of the fruit wall showed disordered array and shape. The creep-extension analysis indicated that the elongating flower stem of trg1/xyl1 had lower elasticity and viscosity values than wild type. These results suggest that XGOs have enhancing role on cell wall loosening, and α-xylosidase plays a role to keep cell wall loosening state normal during cell elongation.
