Abstract
To investigate the transcriptional regulation of nutrient uptake processes, we performed a large-scale RT-PCR-based screening of transcription factor mutant collection. All available candidates of transcription factor mutants were collected from RIKEN transposon-tag collection. Mutants were screened by quantifying the transcript abundance of NRT2;1 nitrate transporter. In this study, we isolated an AGL21 knockout mutant in which the accumulation of NRT2;1 was increased as compared with the wild-type plants. AGL21 belongs to MADS-box gene family, categorized as one of the 12 root-expressed genes in this family, and is grouped in an ANR1 clade. ANR1 is a key regulator of a signaling pathway which regulates lateral root growth in response to local nitrate supply. The AGL21 knockout mutant showed severe inhibition of primary root elongation under low nitrogen conditions. Our results suggest that AGL21 is a novel transcription factor essentially required for the maintenance of root growth under low nitrogen environment.
