Abstract
NOB is a line of transgenic Arabidopsis that expresses GFP according to sulfur status (*1). From NOB M2, nbm2(NOB mutant 2) -1 and 2 were isolated, in which GFP fluorescence increased. NBM2 locus was mapped to a 55 kb region on the chromosome 3, containing ten genes, including BIG. Phenotypes of the big mutants (*2) were similar to nbm2. Independent nonsense mutations were found in the BIG ORF of nbm2 mutants. In nbm2-2, concentrations of sulfate and glutathione did not significantly change, but concentration of nitrate decreased. Additionally, cysteine content was reduced, while γ-EC content was increased to some extents. Accumulation of mRNA corresponding to the γ-EC synthetase gene was elevated in nbm2. Polar auxin transport (PAT) is deficient in the big mutant. Possible relationship between PAT and sulfur deficiency response are being investigated.
*1 Ohkama et al. (2002) PCP 43,1493-1501: *2 Gil et al. (2001) Genes Dev. 15:1985-1997
