Summary 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.faNTA was used as a tool to manipulate Ca2+influx infermutants. Light sheet fluorescence imaging was used to image the reporter R‐GECO1 to observe [Ca2+]cytdynamics during root hair elongation in various genotypes.We show that faNTA is sufficient to restore normal root hair development, [Ca2+]cytoscillations, and ROS levels tofer‐4. MLO15 was identified as a regulator of root hair tip growth based on disrupted root hair growth and [Ca2+]cytsignatures inmlo15‐4. We also link the FER/MLO module to ROS accumulation by showing that faNTA is sufficient to restore ROS levels infer‐4root hairs, but is unable to complement the burst root hairs ofrbohc.We propose that MLOs act downstream of FER to mediate Ca2+influx and promote ROS production to regulate root hair tip growth.
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A temperature-sensitive FERONIA mutant allele that alters root hair growth
Abstract In plants, root hairs undergo a highly polarized form of cell expansion called tip-growth, in which cell wall deposition is restricted to the root hair apex. In order to identify essential cellular components that might have been missed in earlier genetic screens, we identified conditional temperature-sensitive (ts) root hair mutants by ethyl methanesulfonate mutagenesis in Arabidopsis thaliana. Here, we describe one of these mutants, feronia-temperature sensitive (fer-ts). Mutant fer-ts seedlings were unaffected at normal temperatures (20°C), but failed to form root hairs at elevated temperatures (30°C). Map based-cloning and whole-genome sequencing revealed that fer-ts resulted from a G41S substitution in the extracellular domain of FERONIA (FER). A functional fluorescent fusion of FER containing the fer-ts mutation localized to plasma membranes, but was subject to enhanced protein turnover at elevated temperatures. While tip-growth was rapidly inhibited by addition of rapid alkalinization factor 1 (RALF1) peptides in both wild-type and fer-ts mutants at normal temperatures, root elongation of fer-ts seedlings was resistant to added RALF1 peptide at elevated temperatures. Additionally, at elevated temperatures fer-ts seedlings displayed altered reactive oxygen species (ROS) accumulation upon auxin treatment and phenocopied constitutive fer mutant responses to a variety of plant hormone treatments. Molecular modeling and sequence comparison with other Catharanthus roseus receptor-like kinase 1L (CrRLK1L) receptor family members revealed that the mutated glycine in fer-ts is highly conserved, but is not located within the recently characterized RALF23 and LORELI-LIKE-GLYCOPROTEIN 2 binding domains, perhaps suggesting that fer-ts phenotypes may not be directly due to loss of binding to RALF1 peptides.
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- PAR ID:
- 10281774
- Date Published:
- Journal Name:
- Plant Physiology
- Volume:
- 185
- Issue:
- 2
- ISSN:
- 0032-0889
- Page Range / eLocation ID:
- 405 to 423
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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