Abstract
Sulfur is an essential nutrient required for plant growth. Plants have developed a regulatory mechanism that activates sulfur assimilation for survival under sulfur deficiency (-S). However, the molecular mechanisms controlling the -S-inducible gene expression is almost unknown. To identify the key regulator, we isolated Arabidopsis mutants showing aberrant responses to -S. The expression of SULTR1;2 sulfate transporter was visualized as GFP fluorescence in a transgenic plant expressing SULTR1;2 promoter-GFP fusion gene. This plant was used as a parental line for the EMS mutagenesis. The isolated mutant, slim1, lacked the -S response of SULTR1;2 expression. SLIM1 encoded a transcription factor localized in the nucleus. Microarray analysis of the slim1 mutant indicated that majority of the -S-responsive genes were regulated by SLIM1. The plant growth on -S was affected by the slim1 mutation, but was stimulated by over-expression of SLIM1. These results indicate that SLIM1 is a positive regulator of -S response.
