Nodule development in Medicago truncatula is promoted by EPIDERMAL PATTERNING FACTOR-LIKE peptides

Area of Science:

• Plant Biology
• Molecular Plant-Microbe Interactions
• Symbiosis Research

Background:

• Epidermal Patterning Factor-Like (EPFL) peptides regulate plant development, particularly stomatal formation.
• The functions of EPFL peptides in below-ground processes, such as symbiotic interactions, are not well understood.

Purpose of the Study:

• To investigate the role of Medicago truncatula EPFL peptides (MtEPFL9 and MtEPFL14) in nodule organogenesis during nitrogen-fixing symbiosis.
• To elucidate the molecular mechanisms by which these peptides regulate symbiotic development.

Main Methods:

• Gene expression analysis of MtEPFL9 and MtEPFL14 in response to rhizobia and Nod factors.
• Application of synthetic MtEPFL peptides to assess their effects on root development and nodulation.
• Phenotypic analysis of mutant lines (nf-ya1, noot1/noot2) treated with MtEPFL peptides.
• Transcriptomic analysis to identify signaling pathways regulated by MtEPFL peptides.

Main Results:

• MtEPFL9 and MtEPFL14 genes are transcriptionally induced by rhizobia and Nod factors via a common symbiosis signaling pathway.
• Exogenous MtEPFL9 and MtEPFL14 peptides enhance root development and nodule formation by promoting cell division and growth.
• MtEPFL peptides partially rescue nodulation defects in nf-ya1 mutants and suppress nodule-to-root conversion in noot1/noot2 mutants.
• Transcriptomic data indicate MtEPFL peptides modulate rhizobia-induced signaling pathways involving gibberellin, auxin, and cytokinin.

Conclusions:

• MtEPFL9 and MtEPFL14 are identified as positive regulators of nodule organogenesis in Medicago truncatula.
• These EPFL peptides are crucial for regulating meristematic activity and organ growth in symbiotic nodules and lateral roots.
• The study reveals novel roles for EPFL peptides as host-derived signals that promote symbiotic organogenesis.