Summary
Group VII Ethylene Response Factors (ERF-VII) are plant-specific
transcription factors (TFs) known for their role in the activation of
hypoxia-responsive genes under low oxygen stress but also in plant
endogenous hypoxic niches. However, their function in the
microaerophilic nitrogen-fixing nodules of legumes has not yet been
investigated. We investigated regulation and the function of the twoMedicago truncatula ERF-VII TFs (MtERF74 andMtERF75 ) in roots and nodules, MtERF74 and MtERF75in response to hypoxia stress and during the nodulation process using an
RNA interference strategy and targeted proteolysis of MtERF75.
Knockdown of MtERF74 and MtERF75 partially blocked the
induction of hypoxia-responsive genes in roots exposed to hypoxia
stress. In addition, a significant reduction in nodulation capacity and
nitrogen fixation activity was observed in mature nodules of double
knockdown transgenic roots. Overall, the results indicate that MtERF74
and MtERF75 are involved in the induction of MtNR1 andPgb1.1 expression for efficient Phytogb-NO respiration in the
nodule.
Keywords: Ethylene Response Factors Group VII family; hypoxia-responsive
genes (HRGs); N-degron; nitrogen fixation; O2-sensing;
hypoxia stress; Rhizobium legumes symbiosis