Rice Defense Responses Orchestrated by Oral Bacteria of the Rice Striped Stem Borer, Chilo suppressalis

Abstract

Plant defenses in response to chewing insects are generally regulated by jasmonic acid (JA) signaling pathway, whereas salicylic acid (SA) signaling is mainly involved in plant defense against biotrophic pathogens and piercing-sucking insects. Previous studies showed that both JA- and SA-related defenses in rice plants were triggered by the infestation of the rice striped stem borer (SSB, Chilo suppressalis), a destructive pest causing severe damage to rice production. Herbivore-associated microbes play an important role in modulating plant–insect interaction, and thus we speculate that the SSB symbiotic microbes acting as a hidden player may cause this anomalous result. The antibiotics (AB) treatment significantly depressed the performance of field-collected SSB larvae on rice plants, and reduced the quantities of bacteria around the wounds of rice stems compared to non-AB treatment. In response to mechanical wounding and oral secretions (OS) collected from non-AB treated larvae, rice plants exhibited lower levels of JA-regulated defenses, but higher levels of SA-regulated defenses compared to the treatment of OS from AB-treated larvae determined by using a combination of biochemical and molecular methods. Among seven culturable bacteria isolated from the OS of SSB larvae, Enterobacter and Acinetobacter contributed to the suppression of JA signaling-related defenses in rice plants, and axenic larvae reinoculated with these two strains displayed better performance on rice plants. Our findings demonstrate that SSB larvae exploit oral secreted bacteria to interfere with plant anti-herbivore defense and avoid fully activating the JA-regulated antiherbivore defenses of rice plants.

Early transcriptomic responses of rice leaves to herbivory by Spodoptera frugiperda

“…To understand the multitrophic interaction between FAW, its oral microbiota and rice, it would be relevant to focus further studies on JA, the central hormone of the response to herbivory. In particular, by studying the ability of the FAW bacterial microbiota to suppress the JA pathway in rice, as has been shown in response to C. suppresalis attack 25 , as well as to study the impact of JA on FAW fitness.…”

“…Rice can also recognize elicitors from the OS of various herbivores such as Spodoptera mauritia (Boisduval, 1833), Mythimna loreyi (Duponchel, 1827), and Parnara guttata (Bremer & Grey, 1852) and, in response, accumulates higher levels of JA/JA-Ile (jasmonate-isoleucin) and/or defense related secondary metabolites compared with wounding alone 22 , 23 . SSB larvae also increase JA levels in rice 24 and induce the expression of OsLOX9 and OsAOS2 , two genes encoding enzymes involved in the biosynthesis of JA 25 . Salicylic acid (SA) is also induced by herbivory.…”

“…Salicylic acid (SA) is also induced by herbivory. Upon SSB attack, the OsPAL1 and OsPR-1a genes, involved in the SA signaling pathway, are induced 24 h after treatment 25 . ET is also induced in rice by SSB and Mythimna separata (Walker, 1865) 26 .…”

Herbivory by Striped Stem Borer Triggers Polyamine Accumulation in Host Rice Plants to Promote Its Larval Growth

“…The laboratory-maintained rice striped stem borer ( Chilo suppressalis , SSB) colony, generously provided by Prof. Yunhe Li from the Institute of Plant Protection, Chinese Academy of Agricultural Sciences, was used in this study. SSB larvae were reared on an artificial diet following Xue et al [ 42 ] and kept in an insectary under a 12 h/12 h day/night cycle, with the temperature at 25–27 °C, and a relative humidity of 70–80%. Thirty third-instar larvae (each weighing approximately 20 mg) were fixed on the main stems of 30-d-old rice plants (one larva per plant) using a plastic tube (D × L: 3 cm × 6 cm) sealed at both ends with cotton (SSB).…”