Diffusible signals in associations of rice with arbuscular mycorrhizal fungi

Arbuscular mycorrhization (AM) is a beneficial root endosymbiosis which is initiated by plant perception of microbe produced signaling molecules, referred to as Myc factors. These signals are lipo-chito-oligosaccharides (LCOs), but AM fungi also produce chitin oligosaccharides (COs). We found that rice roots respond to both LCOs and COs with enhanced lateral root development, similar to the effect of colonization by mycorrhizal fungi. This response was dependent upon the symbiotic signaling proteins DMI3 and POLLUX. Using RNAseq we have also identified genes which are differentially expressed in response to these signals. Our results suggest that the perception of CO4 and CO8 results in similar host genetic regulation, however S-LCOs induce an opposite response.  These findings indicate that rice can perceive and respond to COs and LCOs by altering root morphology, and that this response is mediated by the mycorrhizal signaling pathway.