IDD10 is Involved in the Interaction between NH4 (+) and Auxin Signaling in Rice Roots

摘要

NH4 (+) is an important nitrogen resource for rice plants in paddy soil. Therefore, it is likely that NH4 (+)-triggered plant growth interacts with phytohormone-mediated developmental mechanisms. Our previous transcriptomic analysis revealed that many genes involved in auxin signaling and efflux are sensitive to NH4 (+). In the current study, we found that NH4 (+) treatment causes a delayed gravity response in rice roots. To further elucidate the interlocking relationship between NH4 (+) and auxin signaling during root development, we utilized mutants and overexpressors of a key NH4 (+) signaling transcription factor INDETERMINATE DOMAIN 10 (IDD10), encoding a transcription factor that regulates the expression of NH4 (+) uptake and N-assimilation genes. We obtained several lines of evidence that auxin affects NH4 (+)-mediated gene expression and root development in rice plants via IDD10. First, the gravity response was delayed in idd10 roots and accelerated in IDD10 overexpressor (IDD10 OX) roots in the absence and (especially) presence of NH4 (+). Second, idd10 plants showed strong root coiling only in the presence of NH4 (+). However, treatment of 1-N-naphthylphthalamic acid (NPA), a polar auxin transport inhibitor suppressed the NH4 (+)-specific root phenotype of idd10. Third, the expression of NH4 (+)-responsive auxin-related genes was affected in idd10 and IDD10 overexpressors. Finally, IDD10 expression was induced by IAA and suppressed by NPA. These findings suggest that the gene expression patterns and phenotypes triggered by NH4 (+) are influenced by the actions of auxin during root development, pointing to a regulatory circuit between NH4 (+) and auxin signaling that functions in root development in rice.