DELLA proteins are common components of symbiotic rhizobial and mycorrhizal signalling pathways

Nat Commun. 2016 Aug 12;7:12433. doi: 10.1038/ncomms12433.

Abstract

Legumes form symbiotic associations with either nitrogen-fixing bacteria or arbuscular mycorrhizal fungi. Formation of these two symbioses is regulated by a common set of signalling components that act downstream of recognition of rhizobia or mycorrhizae by host plants. Central to these pathways is the calcium and calmodulin-dependent protein kinase (CCaMK)-IPD3 complex which initiates nodule organogenesis following calcium oscillations in the host nucleus. However, downstream signalling events are not fully understood. Here we show that Medicago truncatula DELLA proteins, which are the central regulators of gibberellic acid signalling, positively regulate rhizobial symbiosis. Rhizobia colonization is impaired in della mutants and we provide evidence that DELLAs can promote CCaMK-IPD3 complex formation and increase the phosphorylation state of IPD3. DELLAs can also interact with NSP2-NSP1 and enhance the expression of Nod-factor-inducible genes in protoplasts. We show that DELLA is able to bridge a protein complex containing IPD3 and NSP2. Our results suggest a transcriptional framework for regulation of root nodule symbiosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism
  • Gene Expression Regulation, Plant
  • Medicago truncatula / microbiology
  • Medicago truncatula / physiology*
  • Mutation
  • Mycorrhizae / physiology*
  • Phosphorylation
  • Plant Proteins / genetics
  • Plant Proteins / metabolism*
  • Rhizobium / physiology*
  • Root Nodules, Plant / microbiology
  • Root Nodules, Plant / physiology
  • Signal Transduction / physiology
  • Symbiosis / physiology*

Substances

  • Plant Proteins
  • Calcium-Calmodulin-Dependent Protein Kinases