The rice transcription factor Nhd1 regulates root growth and nitrogen uptake by activating nitrogen transporters
Kangning Li, Shunan Zhang, Shuo Tang, Jun Zhang, Hongzhang Dong, Shihan Yang, Hongye Qu, Wei Xuan, Mian Gu, Guohua Xu
Abstract
Plants adjust root architecture and nitrogen (N) transporter activity to meet the variable N demand, but their integrated regulatory mechanism remains unclear. We have previously reported that a floral factor in rice (Oryza sativa), N-mediated heading date-1 (Nhd1), regulates flowering time. Here, we show that Nhd1 can directly activate the transcription of the high-affinity ammonium (NH4+) transporter 1;3 (OsAMT1;3) and the dual affinity nitrate (NO3-) transporter 2.4 (OsNRT2.4). Knockout of Nhd1 inhibited root growth in the presence of NO3- or a low concentration of NH4+. Compared to the wild-type (WT), nhd1 and osamt1;3 mutants showed a similar decrease in root growth and N uptake under low NH4+ supply, while nhd1 and osnrt2.4 mutants showed comparable root inhibition and altered NO3- translocation in shoots. The defects of nhd1 mutants in NH4+ uptake and root growth response to various N supplies were restored by overexpression of OsAMT1;3 or OsNRT2.4. However, when grown in a paddy field with low N availability, nhd1 mutants accumulated more N and achieved a higher N uptake efficiency (NUpE) due to the delayed flowering time and prolonged growth period. Our findings reveal a molecular mechanism underlying the growth duration-dependent NUpE.