No abstract

Nitrate (NO3-) plays a pivotal role in stimulating lateral root (LR) formation and growth in plants. However, the role of NO3- in modulating rice LR formation and the signalling pathways involved in this process remain unclear. Phenotypic and genetic analyses of rice were used to explore the role of strigolactones (SLs) and auxin in NO3--modulated LR formation in rice. Compared with ammonium (NH4+), NO3- stimulated LR initiation due to higher short-term root IAA levels. However, this stimulation vanished after 7 d, and the LR density was reduced, in parallel with the auxin levels. Application of the exogenous auxin α-naphthylacetic acid to NH4+-treated rice plants promoted LR initiation to levels similar to those under NO3- at 7 d; conversely, the application of the SL analogue GR24 to NH4+-treated rice inhibited LR initiation to levels similar to those under NO3- supply by reducing the root auxin levels at 14 d. D10 and D14 mutations caused loss of sensitivity of the LR formation response to NO3-. The application of NO3- and GR24 downregulated the transcription of PIN-FORMED 2(PIN2), an auxin efflux carrier in roots. LR number and density in pin2 mutant lines were insensitive to NO3- treatment. These results indicate that NO3- modulates LR formation by affecting the auxin response and transport in rice, with the involvement of SLs.

No abstract

No abstract

SUMMARYNitrogen (N) is a vital major nutrient for rice (Oryza sativa). Rice responds to different applications of N by altering its root morphology, including root elongation. Although ammonium () is the primary source of N for rice, is toxic to rice roots and inhibits root elongation. However, the precise molecular mechanism that ‐inhibited root elongation of rice is not well understood. Here, we identified a rice T‐DNA insert mutant of OsMADS5 with a longer seminal root (SR) under sufficient N conditions. Reverse‐transcription quantitative PCR analysis revealed that the expression level of OsMADS5 was increased under compared with supply. Under conditions, knocking out OsMADS5 (cas9) produced a longer SR, phenocopying osmads5, while there was no significant difference in SR length between wild‐type and cas9 under supply. Moreover, OsMADS5‐overexpression plants displayed the opposite SR phenotype. Further study demonstrated that enhancement of OsMADS5 by supply inhibited rice SR elongation, likely by reducing root meristem activity of root tip, with the involvement of OsCYCB1;1. We also found that OsMADS5 interacted with OsSPL14 and OsSPL17 (OsSPL14/17) to repress their transcriptional activation by attenuating DNA binding ability. Moreover, loss of OsSPL14/17 function in osmads5 eliminated its stimulative effect on SR elongation under conditions, implying OsSPL14/17 may function downstream of OsMADS5 to mediate rice SR elongation under supply. Overall, our results indicate the existence of a novel modulatory pathway in which enhancement of OsMADS5 by supply represses the transcriptional activities of OsSPL14/17 to restrict SR elongation of rice.