Download Lipo-chitooligosaccharides (LCOs) were first identified as secreted

Perception of symbiotic lipo-chitooligosaccharides and chitooligosaccharides by
plants
John A Smith1 and Eric Dupont2
1LRSV,
Université de Toulouse-CNRS, Castanet-Tolosan, France; 2LIPM, INRACNRS, Castanet-Tolosan, France.
Lipo-chitooligosaccharide (LCO) signal molecules were first identified as secreted by
rhizobial bacteria and essential for establishment of the root nodule symbiosis in
many legumes. More recently the arbuscular mycorhizal (AM) fungus Rhizophagus
irregularis was shown to secrete LCOs1, and short chain chitooligosaccharides
(COs)2. In contrast to the rhizobial LCOs, the exact role of fungal LCOs and COs in
symbiosis is not yet known, but their application on different plant species induces
molecular and developmental responses. We aim to better understand the roles of
these fungal molecules by identifying their plant receptors through a combination of
biochemical and reverse genetic approaches. Proteins encoded by the Lysin-Motif
Receptor-Like Kinase (LysM-RLK) and Lysin-Motif Receptor-Like Protein (LysM-RLP)
multigenic families are candidates to be LCO and CO receptors. We have chosen the
dicotyledonous Solanaceae tomato and the monocotyledonous Poaceae
Brachypodium distachyon for reverse genetics. We have also analyzed biochemical
functions of LysM-RLK/Ps from these and additional non-legume plant species. We
are using Virus Induced Gene Silencing to screen for Solanaceae LysM-RLK/Ps
playing major roles in the AM symbiosis. Similarly, B. distachyon lines mutated in
LysM-RLK/Ps are being collected and analyzed for responses to LCOs and COs, and
for their abilities to establish the AM symbiosis. We have shown that a tomato LysMRLK is required for colonization by R. Irregularis. LCO binding assays showed that
various LysM-RLKs have affinity for LCOs, and differences found between species
suggest diverse sensitivities to LCOs between plants.
1Maillet
et al. (2011) Nature 469: 58-63, Genre et al. (2013)
2Genre
et al. (2013) New Phytol 198: 190-202