RALF1 peptide triggers biphasic root growth inhibition upstream of auxin biosynthesis

Abstract

Plant cell growth responds rapidly to various stimuli, adapting architecture to environmental changes. Two major endogenous signals regulating growth are the phytohormone auxin and the secreted peptides rapid alkalinization factors (RALFs). Both trigger very rapid cellular responses and also exert long-term effects [Du et al., Annu. Rev. Plant Biol. 71, 379–402 (2020); Blackburn et al., Plant Physiol. 182, 1657–1666 (2020)]. However, the way, in which these distinct signaling pathways converge to regulate growth, remains unknown. Here, using vertical confocal microscopy combined with a microfluidic chip, we addressed the mechanism of RALF action on growth. We observed correlation between RALF1-induced rapid Arabidopsis thaliana root growth inhibition and apoplast alkalinization during the initial phase of the response, and revealed that RALF1 reversibly inhibits primary root growth through apoplast alkalinization faster than within 1 min. This rapid apoplast alkalinization was the result of RALF1-induced net H + influx and was mediated by the receptor FERONIA (FER). Furthermore, we investigated the cross-talk between RALF1 and the auxin signaling pathways during root growth regulation. The results showed that RALF-FER signaling triggered auxin signaling with a delay of approximately 1 h by up-regulating auxin biosynthesis, thus contributing to sustained RALF1-induced growth inhibition. This biphasic RALF1 action on growth allows plants to respond rapidly to environmental stimuli and also reprogram growth and development in the long term.

Reorganization of three-dimensional chromatin architecture inMedicago truncatulaunder phosphorus deficiency

“…Its homologous gene in Arabidopsis was identified to contain a single nucleotide polymorphism site that was associated with phosphate use efficiency ( El-Soda et al , 2019 ). Chr7g0219691 encodes a feronia receptor-like kinase which regulates root elongation and responds to stresses ( Gigli-Bisceglia et al , 2022 ; Li et al , 2022 ). Moreover, this protein family regulates root microbiome regulation to alleviate phosphate starvation ( Tang et al , 2022 ).…”

Comprehensive Analysis of Peptide-Coding Genes Identifies an LRR-only Microprotein That Regulates Reproductive Organs in Marchantia polymorpha

“…Notably, auxin-responsive genes were significantly repressed in gametophores, suggesting that attenuation of the auxin signal correlates with the transition to the reproductive phase in M. polymorpha (Flores-Sandoval et al, 2018). Additionally, recent studies showed that RALF1-FER inhibited root growth by induction of auxin biosynthesis in A. thaliana (Li et al, 2022), suggesting crosstalk between signaling peptides and phytohormones (Oh et al, 2018).…”

Cell-specific clock-controlled gene expression program regulates rhythmic fiber cell growth in cotton

“…We noted that the GhRALF1 transcription peaks appear to coincide with fiber cell elongation velocity peaks as well as apoplastic pH troughs, probably due to a temporal delay between transcription and physiological consequences as the peptides need time to be translated, secreted, and transduced. Another hypothesis is that GhRALF1 might in vivo promote fiber cell elongation, although a recent study also showed that RALF1 of Arabidopsis also inhibits cell growth in vivo [51]. Whether GhRALF1 promotes or inhibits the growth of cotton fiber cells in vivo remains to be elucidated by further studies.…”