Abscisic Acid Coordinates Nod Factor and Cytokinin Signaling during the Regulation of Nodulation in Medicago truncatula

We show that application of abscisic acid inhibits nodulation, bacterial infection, and nodulin gene expression in Medicago truncatula

Yiliang Ding; Peter Kalo; Craig Yendrek; Jongho Sun; Yan Liang; John F. Marsh; Jeanne M. Harris; Giles E.D. Oldroyd

2008

Scholarcy highlights

  • The availability of nitrogen is crucial for plant growth, and legumes have evolved the capability to interact with nitrogenfixing rhizobial bacteria to provide a ready source of this nutrient
  • We have previously shown that ethylene and jasmonic acid are negative regulators of the Nod factor signaling pathway acting at or upstream of calcium spiking
  • It has previously been suggested that abscisic acid may regulate nodulation responses in root hair cells, and consistent with this, we found that external application of ABA is able to abolish both Nod factor–induced calcium spiking and gene expression
  • The effects of ABA on calcium spiking are similar to what we have previously observed with JA: high concentrations of ABA abolish calcium spiking, while lower concentrations impact the period between calcium spikes
  • Increasing the Nod factor concentration overwhelmed ABA inhibition allowing a recovery in calcium spiking, suggesting that the activation of Nod factor signaling is balanced between the ABA and Nod factor concentrations
  • These results indicate that ABA, like ethylene and JA, can inhibit Nod factor signaling at or above calcium spiking
  • The fact that the reduced nodulation mutant sta-1 is insensitive to abscisic acid for the regulation of Nod factor responses in epidermal cells, but hypersensitive to ABA for cytokinin induction of ENOD40 and NIN in cortical cells, highlights the importance of ABA regulation of cytokinin responses in the cortex during the regulation of

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