The D3 F-box protein is a key component in host strigolactone responses essential for arbuscular mycorrhizal symbiosis.

ABSTRACT

Arbuscular mycorrhiza (AM) represents an ancient endosymbiosis between plant roots and Glomeromycota fungi. Strigolactones (SLs), plant-derived terpenoid lactones, activate hyphal branching of AM fungi before physical contact. Lack of SL biosynthesis results in lower colonization of AM fungi. The F-box protein, DWARF3 (D3), and the hydrolase family protein DWARF14 (D14) are crucial for SL responses in rice. Here we conducted AM fungal colonization assays with the SL-insensitive d3 and d14 mutants. The d3 mutant exhibited strong defects in AM fungal colonization, whereas the d14 mutant showed higher AM fungal colonization. As D14 has a homologous protein, D14-LIKE, we generated D14-LIKE knockdown lines by RNA interference in the wildtype and d14 background. D14 and D14-LIKE double knockdown lines exhibited similar colonization rates as those of the d14-1 mutant. D3 is crucial for establishing AM symbiosis in rice, whereas D14 and D14-LIKE are not. Our results suggest distinct roles for these SL-related components in AM symbiosis.