Abstract
Boron (B) is an essential element for higher plants. In general, B deficiency leads to the inhibition of cell elongation in growing tissues. To elucidate the function of B in plants, EMS-mutagenized M2 populations of Arabidopsis thaliana was screened for mutants with altered-root elongation in response to B conditions in media. The isolated mutant showed short roots under normal B (30 μM), while the supply of high B (1 mM) rescued the root elongation partially. Two such lines named brr1-1 and brr2-1 (Boron Root Response) were studied in detail. Both lines carried a single recessive mutation. BRR1 and BRR2 were located on chromosomes 1 and 2, respectively. Under 30 μM B supply, root lengths of brr1-1 and brr2-1 were about 30 and 20% of the wild type, respectively. When 1 mM B was supplied, root lengths of brr1-1 and brr2-1 recovered to 70 and 30% of the wild type, respectively. In brr2-1 B concentration was lower in both roots and shoots, compared with the wild type. These data suggest that the mutants are defective in B utilization for root elongation. We expect that these mutants will reveal new aspects of boron involvement in root elongation.
