Distinct roles for strigolactones in cyst nematode parasitism of Arabidopsis roots

Abstract

Phytohormones play an essential role in different stages of plant-nematode interactions. Strigolactones (SLs) are a novel class of plant hormones which play an important role in plant development. Furthermore, certain soil-inhabiting organisms exploit this plant molecule as allelochemical. However, whether SLs play a role in plant parasitism by nematodes is as yet unknown. This prompted us to investigate the potential role of SLs in different stages of the nematode life cycle using the beet cyst nematode Heterodera schachtii and Arabidopsis as a model system. We analyzed the effect of SLs on cyst nematode hatching, host attraction and invasion, and the establishment of a feeding relation upon infection of the SL deficient mutant max4-1 and the SL signaling mutant max2-1. In addition, infection assays were performed under phosphate shortage to enhance SL production and in the presence of the synthetic SL analog GR24. From this study, we can conclude that SLs do not contribute to cyst nematode hatching at the levels tested but that they do play a role in host attraction and subsequent invasion in a MAX2 dependent manner. Furthermore, we observed that increased levels of exogenous and endogenous SLs change the root invasion zone. Upon root infection, cyst nematode development was enhanced in both the max2-1 and max4-1 mutants due to the formation of enlarged feeding cells. These data provide evidence for distinct roles of SLs during cyst nematode parasitism of plant roots.

Biological Control of Plant-Parasitic Nematodes by Filamentous Fungi Inducers of Resistance: Trichoderma, Mycorrhizal and Endophytic Fungi

“…Concerning hormones not directly related to plant defensive responses, it is known that strigolactones, after being exuded from the root, activate hyphal branching and enhanced growth and energy metabolism of symbiotic AMF, and once the symbiosis is established, its production by the plant roots fades (Rochange et al, 2019). Regarding the nematodes, it has been proven that the strigolactones do not contribute to cyst nematode (Heterodera schachtii) hatching but they do play a role in host attraction and subsequent invasion (Martinez et al, 2019). In rice, signaling mediated by strigolactones suppresses jasmonate accumulation and promotes RKN infection (Lahari et al, 2019).…”

“…on A. thaliana roots. Once the symbiosis is established, the fungi decompose strigolactones in planta and downregulate the expression of strigolactones biosynthesis genes (Rozpądek et al, 2018), preventing, therefore, root invasion by nematodes (Martinez et al, 2019).…”

Cyst nematode bio‐communication with plants: implications for novel management approaches

“…Ethylene signaling reduces H. glycines attraction to host roots, 52,55 unlike with H. schachtii for which ethylene signal transduction increases plant susceptibility 53 . Disruption of strigolactone signaling also compromises H. schachtii attraction to Arabidopsis roots 56 . ABC transporter genes modulate composition of root diffusates with knockdown of ABC‐G33 and ABC‐C6 in tomato, resulting in hatch inhibition and repulsion of both G. rostochiensis and G. pallida 57 .…”

Impacts of Root Metabolites on Soil Nematodes

“…In a bioassay, ethephon, methyl jasmonate, salicylic acid, indole acetic acid, and mannitol showed positive chemotaxis of G. pallida J2s (Fleming et al, 2017). In in vitro nematode infection assays, Arabidopsis mutants with a strigolactone signaling pathway deficiency reduced attraction and invasion by the cyst nematode Heterodera schachtii compared to the wildtype plant (Escudero Martinez et al, 2019).…”