Discovery of SOD5 as a novel regulator of nitrogen‐use efficiency and grain yield via altering auxin level

Auxin has emerged as a crucial regulator of plant nitrogen (N)-use efficiency (NUE) through indirect effects on plant growth and development and direct regulation of N metabolism-related genes. We previously reported DULL NITROGEN RESPONSE1 (DNR1) as an amino transferase that inhibits auxin accumulation and negatively regulates rice (Oryza sativa) NUE and grain yield. However, the identities of molecular regulators acting upstream of DNR1 await exploration. Our current work identifies SUPPRESSOR OF DNR1 ON CHROMOSOME 5 (SOD5) from a DNR1 suppressor mutant. SOD5 encodes a v-myb avian myeloblastosis viral oncogene homolog (MYB) transcription factor that directly binds to the DNR1 promoter, activating its expression and further repressing auxin accumulation. Knocking out SOD5 significantly increases NUE and grain yield, especially under low N conditions. Therefore, targeting SOD5 offers a promising strategy for enhancing crop performance, supporting the development of crops better suited for sustainable agriculture.