Journal Article<scp>MLO</scp> ‐mediated Ca 2+ influx regulates root hair tip growth in ArabidopsisOgawa, Sienna T [Purdue Center for Plant Biology Purdue University 915 Mitch Daniels Blvd West Lafayette IN 47907 USA] (ORCID:0000000169817113); Zhang, Weiwei [EMBRIO Institute Purdue University 207 S. Martin Jischke Ave West Lafayette IN 47907 USA] (ORCID:0000000247546241); Staiger, Christopher J [EMBRIO Institute Purdue University 207 S. Martin Jischke Ave West Lafayette IN 47907 USA] (ORCID:0000000323211671); Kessler, Sharon A [Purdue Center for Plant Biology Purdue University 915 Mitch Daniels Blvd West Lafayette IN 47907 USA] (ORCID:0000000279640451)<title>Summary</title> <list list-type='bullet'><list-item>Root hair tip‐growth involves coordinated Ca2+and ROS signaling to promote growth while maintaining tip integrity. MILDEW RESISTANCE LOCUS‐O (MLO) proteins act downstream of FERONIA (FER) receptor‐like kinases in pollen tubes and synergids to regulate calcium dynamics. This study uses a constitutively active MLO (faNTA) to identify a new role for the FER/MLO signaling module in regulating [Ca2+]cytoscillations in growing root hairs.</list-item><list-item>faNTA was used as a tool to manipulate Ca2+influx in<italic>fer</italic>mutants. Light sheet fluorescence imaging was used to image the reporter R‐GECO1 to observe [Ca2+]cytdynamics during root hair elongation in various genotypes.</list-item><list-item>We show that faNTA is sufficient to restore normal root hair development, [Ca2+]cytoscillations, and ROS levels to<italic>fer‐4</italic>. MLO15 was identified as a regulator of root hair tip growth based on disrupted root hair growth and [Ca2+]cytsignatures in<italic>mlo15‐4</italic>. We also link the FER/MLO module to ROS accumulation by showing that faNTA is sufficient to restore ROS levels in<italic>fer‐4</italic>root hairs, but is unable to complement the burst root hairs of<italic>rbohc.</italic></list-item><list-item>We propose that MLOs act downstream of FER to mediate Ca2+influx and promote ROS production to regulate root hair tip growth.</list-item></list>Wiley, New Phytologist Foundation2025-12-0110672196New Phytologist24863024 to 30390028-646Xhttps://doi.org/10.1111/nph.703782224038National Science Foundation