OsEIL1 is involved in the response to heterogeneous high ammonium in rice: A split-root analysis

Ammonium (NH₄⁺) concentrations in rice fields show heterogeneous spatial distribution under the combined influences of nitrogen fertilizer application and modern agronomic practices. However, the characteristics and mechanisms of rice roots in response to heterogeneous NH₄⁺ supply are not well understood. Here, we found a systemic response of rice roots to heterogeneous and high (10 mM) NH₄⁺ supply using a split-root experiment, and show root growth on the NH₄⁺-free (NO₃^-) side was also inhibited by localized high-NH₄⁺ supply. Moreover, OsEIL1 (encoding a core transcription factor in the ethylene signaling pathway) was found to be involved in the response of rice roots to heterogeneous NH₄⁺. OsEIL1 mutation significantly increased the inhibitory effect of localized high-NH₄⁺ on root growth of the NO₃^- side, as well as significantly increased NH₄⁺ efflux there. Furthermore, our results indicate that the mitigating effect of OsEIL1 on NH₄⁺ efflux is related to the regulated expression of OsVTC1-3 (encoding a GDP-mannose pyrophosphorylase). These findings provide insight into the mechanisms by which OsEIL1 responds to heterogeneous high NH₄⁺ and contribute to our understanding of rice adaptation to heterogeneous NH₄⁺ supply.