Coordinated ethylene and reactive oxygen species signaling regulates root hair morphogenesis for nitrogen acquisition...

Root hairs are crucial for nutrient acquisition and exhibit high developmental plasticity in response to external nutrient availability. However, the specific root hair responses and mechanisms that integrate external nitrogen (N)-limitation signals into the root hair development remain poorly understood. This study revealed that under N deficiency, a set of genes associated with root hair development and ethylene responses was markedly upregulated in Arabidopsis roots. On a molecular level, the transcriptional activity of ETHYLENE INSENSITIVE 3 (EIN3), a master transcription factor of ethylene signaling, was augmented in the root vascular tissues under N deficiency, as shown by the 5×EBS:GUS staining. Further research using the ethylene-insensitive mutant ein3-1eil1-1 exhibited significantly reduced root hair length under low-N conditions. The inhibitory effect was further confirmed by ethylene synthesis inhibitor aminoethoxyvinylglycine (AVG). We also found that low nitrate significantly enriched ROS-related metabolic processes. Subsequent functional analyses revealed that the resulted ROS is specifically required for root hair elongation. Crucially, we demonstrate that ROS accumulation is required for the ethylene-dependent growth of root hairs under N deficiency. Taken together, these results suggest that N deficiency triggers a signaling cascade involving both ethylene and ROS to regulate root hair elongation, thereby enhancing the plant's capacity for nutrient acquisition.