Strigolactone deficiency induces jasmonate, sugar and flavonoid phytoalexin accumulation enhancing rice defense against the blast fungus Pyricularia oryzae

Abstract

Summary Strigolactones (SLs) are carotenoid‐derived phytohormones that regulate plant growth and development. While root‐secreted SLs are well‐known to facilitate plant symbiosis with beneficial microbes, the role of SLs in plant interactions with pathogenic microbes remains largely unexplored. Using genetic and biochemical approaches, we demonstrate a negative role of SLs in rice (Oryza sativa) defense against the blast fungus Pyricularia oryzae (syn. Magnaporthe oryzae). We found that SL biosynthesis and perception mutants, and wild‐type (WT) plants after chemical inhibition of SLs, were less susceptible to P. oryzae. Strigolactone deficiency also resulted in a higher accumulation of jasmonates, soluble sugars and flavonoid phytoalexins in rice leaves. Likewise, in response to P. oryzae infection, SL signaling was downregulated, while jasmonate and sugar content increased markedly. The jar1 mutant unable to synthesize jasmonoyl‐l‐isoleucine, and the coi1‐18 RNAi line perturbed in jasmonate signaling, both accumulated lower levels of sugars. However, when WT seedlings were sprayed with glucose or sucrose, jasmonate accumulation increased, suggesting a reciprocal positive interplay between jasmonates and sugars. Finally, we showed that functional jasmonate signaling is necessary for SL deficiency to induce rice defense against P. oryzae. We conclude that a reduction in rice SL content reduces P. oryzae susceptibility by activating jasmonate and sugar signaling pathways, and flavonoid phytoalexin accumulation.

The phenylalanine ammonia‐lyase inhibitor AIP induces rice defence against the root‐knot nematode Meloidogyne graminicola

“…To quantify naringenin and sakuranetin, the 1260 HPLC‐QTRAP 6500 mass spectrometer system equipped with a turbo‐spray ion source was operated in positive ionization mode, as detailed in Lahari et al. (2024). The concentrations of naringenin and sakuranetin were determined by comparison to D 6 ‐ABA, applying the experimental response factors.…”

“…(1998) reported that JA increases the activity of PAL enzymes in tobacco and the accumulation of phenylpropanoids like coumarin and scopoletin. In rice, JA is known to enhance the accumulation of phenylpropanoid pathway‐derived phytoalexins, including naringenin and sakuranetin, enhancing defence against blast fungus (Lahari et al., 2024; Ogawa et al., 2017). On the other hand, an earlier study shows that the activation of the phenylpropanoid pathway leads to a decrease in JA concentration and downstream signalling (Alon et al., 2013), indicating complex relationships between both pathways.…”

Chemically Mediated Plant–Plant Interactions: Allelopathy and Allelobiosis

“…Additionally, AtD14, MAX2 encoding an F-box protein, and the transcription factors BRC1/2 are involved in the strigolactone signaling pathway in Arabidopsis [ 251 ]. Strigolactones not only participate in stimulating the germination of parasitic plants like striga but also play a crucial role in the symbiosis between plant roots and arbuscular mycorrhizal fungi [ 252 ]. Recent studies have found that root-secreted strigolactones promote plant symbiosis with beneficial microorganisms and participate in the interaction between plants and pathogenic microorganisms.…”

“…For example, SLs play a negative regulatory role in the defense of rice against the rice blast fungus ( pyricaria oryzae ). The reduction in strigolactone levels in rice enhances its defense against the rice blast fungus by activating jasmonic acid and sugar signaling pathways, as well as accumulating flavonoid phytoalexins [ 252 ].…”

The link between changing in host carbon allocation and resistance to Magnaporthe oryzae : a possible tactic for mitigating the rice blast fungus

“…Studying the relationship between alterations in carbon allocation and resistance to M. oryzae will be crucial to comprehend the molecular processes that underlie plant defense reactions. 25 , 31 , 62 The goal of these investigations is to understand how changes in the carbon distribution of resources affect a plant’s capacity to fend off and defeat the invasive pathogen. Future research should examine how dynamic changes in carbon allocation patterns occur during rice blast infections, with an emphasis on how photosynthetically fixed carbon is redistributed to areas that are being attacked by pathogens.…”