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

• Published in: Nature communications Vol. 11; no. 1; p. 2114
• Main Authors: Choi, Jeongmin, Lee, Tak, Cho, Jungnam, Servante, Emily K., Pucker, Boas, Summers, William, Bowden, Sarah, Rahimi, Mehran, An, Kyungsook, An, Gynheung, Bouwmeester, Harro J., Wallington, Emma J., Oldroyd, Giles, Paszkowski, Uta
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 30-04-2020; Nature Publishing Group; Nature Portfolio
• Subjects: 14/19; 38/77; 38/91; 45; 45/70; 631/449; 631/449/2676; 631/449/2676/2061; 96/95; Arabidopsis - genetics; Arabidopsis - microbiology; Arabidopsis Proteins - genetics; Arabidopsis Proteins - physiology; Arbuscular mycorrhizas; Biosynthesis; Colonization; Crosstalk; Down-regulation; Fungi; Furans - metabolism; Gene Expression Regulation, Plant; Germination; Heterocyclic Compounds, 3-Ring - metabolism; Homology; Homozygote; Humanities and Social Sciences; Intracellular Signaling Peptides and Proteins - genetics; Intracellular Signaling Peptides and Proteins - physiology; Lactones - metabolism; multidisciplinary; Multigene Family; Mycorrhizae - physiology; Oryza - genetics; Oryza - microbiology; Phylogeny; Phytohormones; Plant Proteins - genetics; Plant Proteins - physiology; Plant Roots - microbiology; Pyrans - metabolism; Receptors; Rice; RNA-Seq; Science; Science (multidisciplinary); Signal Transduction; Signaling; Soil microorganisms; Symbiosis; Transcription
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-020-16021-1

Most plants associate with beneficial arbuscular mycorrhizal (AM) fungi that facilitate soil nutrient acquisition. Prior to contact, partner recognition triggers reciprocal genetic remodelling to enable colonisation. The plant Dwarf14-Like (D14L) receptor conditions pre-symbiotic perception of AM fungi, and also detects the smoke constituent karrikin. D14L-dependent signalling mechanisms, underpinning AM symbiosis are unknown. Here, 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 (AtSMAX1) that functions in karrikin signalling. We demonstrate that rice SMAX1 is a suppressor of AM symbiosis, negatively regulating fungal colonisation and transcription of crucial signalling components and conserved symbiosis genes. Similarly, rice SMAX1 negatively controls strigolactone biosynthesis, demonstrating an unexpected crosstalk between the strigolactone and karrikin signalling pathways. We conclude that removal of SMAX1, resulting from D14L signalling activation, de-represses essential symbiotic programmes and increases strigolactone hormone production.
Signaling via the D14L karrikin receptor conditions rice roots for association with arbuscular mycorrhizal fungi. Here, Choi
et al
. show that SMAX1, a rice homolog of an Arabidopsis repressor of karrikin signaling, acts downstream of D14L to suppress mycorrhizal symbiosis and strigolactone biosynthesis.