RALF peptides modulate immune response in the moss Physcomitrium patens

Area of Science:

• Plant Biology
• Molecular Biology
• Evolutionary Biology

Background:

• Rapid Alkalinization Factors (RALFs) are peptide families that regulate plant physiology.
• The evolutionary expansion and ancestral roles of RALFs in stress responses remain largely unknown.
• Non-vascular plants offer insights into the ancient functions of RALF peptides.

Purpose of the Study:

• To investigate the role of RALF peptides in coordinating growth and stress responses in the moss Physcomitrium patens.
• To elucidate the function of previously uncharacterized RALF peptides in bryophytes.
• To understand the ancestral functions of RALFs in plant stress adaptation.

Main Methods:

• Quantitative proteomic analysis of PpRALF knockout (KO) lines.
• Phenotypic analysis of KO lines under abiotic and biotic stress conditions.
• Comparative transcriptome analysis of wild-type and PpRALF3 KO plants infected with Fusarium solani.

Main Results:

• Knockout of PpRALF1, 2, and 3 led to the downregulation of M6 metalloprotease and stress-related membrane proteins.
• PpRALF3 plays a significant role in regulating growth under both abiotic and biotic stress.
• PpRALF2 and PpRALF3 KO lines exhibited increased resistance to bacterial and fungal pathogens, indicating a negative regulatory role in immunity.
• Transcriptomic analysis revealed differential gene regulation in the phenylpropanoid pathway and cell wall biogenesis in PpRALF3 KO plants.

Conclusions:

• PpRALF3 is a key regulator of growth and stress responses in Physcomitrium patens.
• RALF peptides are involved in modulating plant immune responses and stress adaptation in early land plants.
• This study provides insights into the ancestral functions of RALF peptides in plant stress response mechanisms.