Evidence for multiple receptors mediating RALF‐triggered Ca2+ signaling and proton pump inhibition. (18th August 2020)

• Record Type: Journal Article
• Authors: Gjetting, Sisse K.; Mahmood, Khalid; Shabala, Lana; Kristensen, Astrid; Shabala, Sergey; Palmgren, Michael; Fuglsang, Anja T.
• Is Part Of: Plant journal. Volume 104:Number 2(2020)
• Page Start: 433
• Page End: 446
• Publication Date: 2020-08-18
• Subjects: apoplastic pH -- cell elongation -- FERONIA -- PSY1 peptide -- proton pump -- receptor kinase -- signaling pathway -- Arabidopsis thaliana; Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.14935
• Languages: English
• ISSNs: 0960-7412

Abstract

SUMMARY: Acidification of the apoplastic space facilitates cell wall loosening and is therefore a key step in cell expansion. PSY1 is a growth‐promoting secreted tyrosine‐sulfated glycopeptide whose receptor directly phosphorylates and activates the plasma membrane H + ‐ATPase, which results in acidification and initiates cellular expansion. Although the mechanism is not clear, the Rapid Alkalinization Factor (RALF) family of small, secreted peptides inhibits the plasma membrane H + ‐ATPase, leading to alkalinization of the apoplastic space and reduced growth. Here we show that treating Arabidopsis thaliana roots with PSY1 induced the transcription of genes encoding the RALF peptides RALF33 and RALFL36. A rapid burst of intracellular Ca 2+ preceded apoplastic alkalinization in roots triggered by RALFs, with peptide‐specific signatures. Ca 2+ channel blockers abolished RALF‐induced alkalinization, indicating that the Ca 2+ signal is an obligatory part of the response and that it precedes alkalinization. As expected, fer mutants deficient in the RALF receptor FERONIA did not respond to RALF33. However, we detected both Ca 2+ and H + signatures in fer mutants upon treatment with RALFL36. Our results suggest that different RALF peptides induce extracellular alkalinization by distinct mechanisms that may involve different receptors. Significance Statement: Secreted peptides from the Rapid Alkalinization Factor (RALF) family raise the pH of the root apoplasmic space, but how RALF peptides inhibit the activity of the plasma membrane H + ATPase is not clear. We show here that two RALF peptides trigger distinct Ca 2+ burst signatures inside the cell upon binding to their cognate receptors, which then leads to H + ATPase inactivation.