A CLE-BAM-CIK signalling module controls root protophloem differentiation in Arabidopsis

Area of Science:

• Plant Biology
• Developmental Biology
• Molecular Signaling

Background:

• CLAVATA3 (CLV3)/EMBRYO SURROUNDING REGION (CLE) peptides regulate plant development, but specific peptides and receptors controlling protophloem differentiation remain unclear.
• Exogenous CLE peptides inhibit protophloem differentiation and cause root meristem consumption, indicating their crucial role.

Purpose of the Study:

• To identify the specific CLE peptides and their receptor complex involved in regulating protophloem differentiation.
• To elucidate the molecular mechanism by which this signaling pathway controls root development.

Main Methods:

• Expression pattern and phylogenetic analyses to identify candidate CLE peptides.
• Genetic analyses (mutant characterization), physiological assays, and protophloem marker observations.
• In vivo interaction assays and in vitro phosphorylation assays.

Main Results:

• CLE25, CLE26, and CLE45 were identified as key peptides regulating protophloem differentiation.
• The receptor complex BARELY ANY MERISTEM1/3 (BAM1/3) and CLV3 INSENSITIVE KINASEs (CIKs) are essential components of this pathway.
• Mutations in CLE25/26/45 or CIK2/3/4/5/6 rescued root defects in brevis radix (brx) and octopus (ops) mutants.
• CLE25/26/45 peptides induced interactions between BAMs and CIKs, enhancing CIK phosphorylation.

Conclusions:

• The CLE25/26/45-BAM1/3-CIK2/3/4/5/6 signaling module suppresses protophloem differentiation.
• This module functions genetically downstream of BRX and OPS, providing a novel regulatory mechanism for root development.