The negative regulator SMAX1 controls mycorrhizal symbiosis and strigolactone biosynthesis in rice

We present the identification of a negative regulator from rice, which operates downstream of the D14L receptor, corresponding to the homologue of the Arabidopsis thaliana Suppressor of MAX2-1 that functions in karrikin signalling

Jeongmin Choi; Tak Lee; Jungnam Cho; Emily K. Servante; Boas Pucker; William Summers; Sarah Bowden; Mehran Rahimi; Kyungsook An; Gynheung An; Harro J. Bouwmeester; Emma J. Wallington; Giles Oldroyd; Uta. Paszkowski

2020

Scholarcy highlights

  • Most plants associate with beneficial arbuscular mycorrhizal fungi that facilitate soil nutrient acquisition
  • The SMXL family was divided into four subclades, corresponding to three known biological roles in karrikin signalling, phloem development, and in SLsignalling
  • Rice SMAX1 consists of three exons, encoding a protein of 1040 amino acids
  • There are three predicted domains with a nuclear localisation signal at the N-terminus, aligning to the functionally characterised NLS from homologous AtSMXL732, and a doubleClpN domain involved in protein interaction of chaperons and two P-loop ATPases
  • We demonstrate that the AM symbiosis depends on double negative regulatory mechanisms that link hormonal and pre-symbiotic signalling
  • As expected d14l and d3 single mutants displayed strong symbiosis defects with below 5% total fungal colonisation; d14l/smax and d3/smax double homozygous mutants had restored fungal colonisation with 84.8% and 79.6%, respectively
  • We identified rice SMAX1 as a suppressor of AM symbiosis development, functioning downstream of the D14L/D3 receptor complex since the SMAX1 mutation fully restored AM fungal colonisation in the d14l and d3 mutant backgrounds
  • BEE 1 DIP1b CBF1/2 CYCLOPS* AP2 Nodulation Signalling Pathway2* AP2 AP2 B-box zinc finger C3HC4 zinc finger B3 auxin response factor 75 Myb-like bHelix-loop-helix propose that an endogenous signal conditions the root for presymbiotic recognition of arbuscular mycorrhizal fungi via activation of the D14Lsignalling pathway leading to elimination of SMAX1 suppression

Need more features? Save interactive summary cards to your Scholarcy Library.