HAR1 receptor kinase links nodule autoregulation with repression of auxin signaling and lateral root development.

Loss of the Lotus japonicus HAR1 receptor kinase causes NF-YA4 overexpression and broad transcriptional changes, boosting auxin signaling and lateral root development.

• Why it matters: Autoregulation of nodulation restricts nitrogen-fixing nodule formation, but how its systemic control evolved and connects to root architecture remains unclear.
• What they did: The study identifies NF-YA4 (and NF-YA1) as HAR1 targets; under nonsymbiotic conditions HAR1 suppresses them via a miR169-dependent mechanism, and grafting tests local versus systemic effects.
• The result: HAR1 constrains NF-YA4-driven branching both locally and from shoots, suggesting AON may have been co-opted from an LRR-RK/miR169/NF-YA module that normally limits lateral root development.

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