Independent signalling cues underpin arbuscular mycorrhizal symbiosis and large lateral root induction in rice

Abstract

Perception of arbuscular mycorrhizal fungi (AMF) triggers distinct plant signalling responses for parallel establishment of symbiosis and induction of lateral root formation. Rice receptor kinase CHITIN ELICITOR RECEPTOR KINASE 1 (CERK1) and α/β-fold hydrolase DWARF14-LIKE (D14L) are involved in pre-symbiotic fungal perception. After 6 wk post-inoculation with Rhizophagus irregularis, root developmental responses, fungal colonization and transcriptional responses were monitored in two independent cerk1 null mutants; a deletion mutant lacking D14L, and with D14L complemented as well as their respective wild-type cultivars (cv Nipponbare and Nihonmasari). Here we show that although essential for symbiosis, D14L is dispensable for AMF-induced root architectural modulation, which conversely relies on CERK1. Our results demonstrate uncoupling of symbiosis and the symbiotic root developmental signalling during pre-symbiosis with CERK1 required for AMF-induced root architectural changes.

Impairment in karrikin but not strigolactone sensing enhances root skewing in Arabidopsis thaliana

“…These two proteins have been implicated in promoting germination, hypocotyl elongation, light response, reducing hyponasty, establishing arbuscular mycorrhizal fungal (AMF) symbiosis, affecting leaf morphology and drought resistance (Nelson et al ., ; Sun and Ni, ; Waters et al ., ; Stanga et al ., ; Gutjahr et al ., ; Li et al ., ; Lee et al ., ). Root‐related phenotypes reported for any mutant deficient in KAI2 include the absence of AMF symbiosis in rice (Gutjahr et al ., ) and a lower large LRD in rice (Chiu et al ., ). The AMF symbiosis seems to be impaired in the early stages of the interactions as no physical contact between plant and fungus or gene expression changes generally triggered by fungal signals could be found.…”

Partner communication and role of nutrients in the arbuscular mycorrhizal symbiosis

“…In addition, it fails to induce lateral roots in response to AMF (Chiu et al, 2018). However, root colonization of oscerk1 is only delayed and not entirely abolished (Miyata et al, 2014;Zhang et al, 2015;Chiu et al, 2018), pointing towards redundant recognition mechanisms. By contrast, OsCEBiP, a LysM RLP, which acts as co-receptor of OsCERK1 in the perception of longchain chitin oligomers from pathogenic fungi (Kaku et al, 2006), is not required for the AM symbiosis and is not essential for Myc-COinduced Ca 2+ spiking (Carotenuto et al, 2017).…”

“…The rice LysM RLK OsCERK1, which has a dual role in both interactions with pathogenic fungi and AMF (Miyata et al, 2014), was shown to play a central role in the perception of Myc-COs because an oscerk1 mutant does not respond to these molecules with Ca 2+ -spiking (Carotenuto et al, 2017). In addition, it fails to induce lateral roots in response to AMF (Chiu et al, 2018). However, root colonization of oscerk1 is only delayed and not entirely abolished (Miyata et al, 2014;Zhang et al, 2015;Chiu et al, 2018), pointing towards redundant recognition mechanisms.…”

Karrikin Signaling Acts Parallel to and Additively with Strigolactone Signaling to Regulate Rice Mesocotyl Elongation in Darkness

“…The karrikin signaling component DWARF 14-LIKE (D14L) is required for colonization of rice roots by AM fungi (Gutjahr et al, 2015b). The D14L-mediated pathway may act in parallel with the CERK1-dependent pathway (Gutjahr et al, 2015b;Chiu et al, 2018). Moreover, the mesocotyls of the d3 mutant are longer than those of other SL pathway mutants, including d10 and d14 (Hu et al, 2010), and loss of function of D14L increases mesocotyl length in the dark (Gutjahr et al, 2015b;Kameoka and Kyozuka, 2015).…”