Abstract
Boron is an essential micronutrient required for plant growth and development. A mutant with inhibited root elongation under boron deficient and normal conditions was isolated from EMS treated Arabidopsis M2 populations. Map-based cloning revealed it is a new allele of mur1 mutants, mur1-9. Arabidopsis mur1-1 is a dwarf mutant with altered cell wall structures, in which L-fucose is partially substituted by L-galactose. In boron deficient condition, root elongation of mur1-9 was inhibited to ~70% and rhamnogalacturonan II (RG-II) borate diester cross-links decreased to ~50% that of wild-type. Interestingly, inhibited root elongation of mur1-9 was recovered by supply the excess boron, but the ratio of cross-liked RG-II did not change significantly. Furthermore, application of L-fucose was also induced root elongation of mur1-9 under low boron condition. These results imply that boron performs important roles in Arabidopsis root elongation through an RGII-independent pathway.
