<div>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 two
<i>Medicago truncatula</i> ERF-VII TFs ( <i>MtERF74</i> and
<i>MtERF75</i>) in roots and nodules, <i>MtERF74</i> and <i>MtERF75</i>
in response to hypoxia stress and during the nodulation process using an
RNA interference strategy and targeted proteolysis of MtERF75. Knockdown
of <i>MtERF74</i> and <i>MtERF75</i> 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 <i>MtNR1</i> and <i>Pgb1.1</i>
expression for efficient Phytogb-NO respiration in the nodule.</div>