Uridine diphosphate glycosyltransferases (UGTs) are multifunctional detoxification enzymes, which are involved in metabolizing various chemicals and contribute to the development of insecticide resistance. However, the possible roles of UGTs in chlorantraniliprole resistance in Chilo suppressalis have rarely been studied in detail. Based on genome data, 24 UGT genes in C. suppressalis belonging to 11 families were identified, which were designated by the UGT nomenclature committee. Synergism assay data suggested that UGTs are potentially involved in chlorantraniliprole resistance in C. suppressalis. CsUGT40AL1 and CsUGT33AG3 were significantly overexpressed in the chlorantraniliprole resistant strain (12.36- and 5.34-fold, respectively). The two UGTs were highly expressed in the larval Malpighian tubules, fat body, and midgut; however, expression was lowest in the head. Injection of individual dsRNAs reduced the expression of the two target genes (by 69.34% and 48.74%, respectively) and caused significant higher larval mortality (81.33% and 54.67%, respectively). Overexpression of CsUGT40AL1 and CsUGT33AG3 was potentially involved in chlorantraniliprole resistance in C. suppressalis, as confirmed by the RNAi assay. Our findings suggest that overexpression of UGTs may contribute to chlorantraniliprole resistance in C. suppressalis.

Plant terpene synthases (TPSs) are key enzymes responsible for terpene biosynthesis, and can play important roles in defense against herbivore attack. In rice, the protein sequence of TPS46 was most closely related to maize TPS10. However, unlike maize tps10, tps46 was also constitutively expressed in rice even in the absence of herbivore attack. Potential roles or constitutive emissions of specific volatiles may due to the constitutive expressions of tps46 in rice. Therefore, in the present study, RNA interference (Ri) and overexpression (Oe) rice lines were generated to investigate the potential function of TPS46 in Oryza sativa sp. japonica. Interestingly, the rice plants become more susceptible to Rhopalosiphum padi when expression of tps46 was silenced compared with Wt in greenhouse conditions. Artificial infestation bioassays further confirmed that Ri rice lines were susceptible to R. padi, whereas Oe rice lines were repellent to R. padi. Based on GC-MS and ToF-MS analysis, a total of eight volatile products catalyzed by TPS46 in rice were identified. Among them, only limonene and Eβf could be detected in all the Ri, Oe, and Wt lines, whereas other six volatiles were only found in the blend of volatiles from Oe lines. Moreover, the amount of constitutive limonene and Eβf in the Ri lines was significantly lower than in Wt lines, while the amounts of these two volatiles in the Oe line were obviously higher than in control rice. Our data suggested that the constitutive emissions of Eβf and limonene regulated by the constitutive expression of tps46 may play a crucial role in rice defense against R. padi. Consequently, tps46 could be a potential target gene to be employed for improving the resistance of plants to aphids.

Chilo suppressalis (Walker; Lepidoptera: Crambidae) is one of the most damaging rice pests in China. Insecticides play a major role in its management. We describe how we monitored the resistance of C. suppressalis to four insecticides in seven field populations from Jiangxi, Hubei, and Hunan Provinces, China, in 2014–2016. The topical application method for resistance monitoring was suitable for triazophos, monosultap, and abamectin. The conventional rice seedling dipping method proved ineffective for testing chlorantraniliprole so the new artificial diet incorporation method was substituted. This new method provided more consistent results than the other methods, once baseline toxicity data had been established. All populations had moderate to high resistance to triazophos from 2014 to 2016. Monosultap resistance in two populations increased from low in 2014 to moderate in 2016 and the other five populations showed moderate to high-level resistance throughout. Abamectin resistance in three populations increased from sensitive or low in 2014 to moderate in 2015–2016, and the other populations had moderate to high levels of resistance. Resistance to chlorantraniliprole increased from sensitive or low in 2014 to moderate to high in 2016. These results suggested that resistance management strategies should be developed according to the needs of a specific location. It was suggested that, in these localities, organophosphate insecticides should be prohibited, the application of nereistoxin, macrolide antibiotic, and diamide insecticides should be limited, and other insecticides, including spinetoram and methoxyfenozide, that exhibited no resistance should be used rationally and in rotation to delay resistance development.

Long non-coding RNAs, referred to as lncRNAs, perform essential functions in some biological processes, including reproduction, metamorphosis, and other critical life functions. Yet, lncRNAs are poorly understood in pesticide resistance, and no reports to date have characterized which lncRNAs are associated with chlorantraniliprole resistance in Chilo suppressalis. Here, RNA-seq was performed on two strains of C. suppressalis exposed to chlorantraniliprole: one is a susceptible strain (S), and the other is a resistant strain (R). In total, 3,470 lncRNAs were identified from 40,573 merged transcripts in six libraries, including 1,879 lincRNAs, 245 intronic lncRNAs, 853 sense lncRNAs, and 493 antisense lncRNAs. Moreover, differential expression analysis revealed 297 and 335 lncRNAs upregulated in S and R strains, respectively. Differentially expressed (DE) lncRNAs are usually assumed to be involved in the chlorantraniliprole resistance in C. suppressalis. As potential targets, adjacent protein-coding genes (within <1000 kb range upstream or downstream of DE lncRNAs), especially detoxification enzyme genes (cytochrome P450s, carboxyl/cholinesterases/esterases, and ATP-binding cassette transporter), were analyzed. Furthermore, the strand-specific RT-PCR was conducted to confirm the transcript orientation of randomly selected 20 DE lincRNAs, and qRT-PCR was carried out to verify the expression status of 8 out of them. MSTRG.25315.3, MSTRG.25315.6, and MSTRG.7482.1 were upregulated in the R strain. Lastly, RNA interference and bioassay analyses indicated overexpressed lincRNA MSTRG.7482.1 was involved in chlorantraniliprole resistance. In conclusion, we represent, for the first time, the genome-wide identification of chlorantraniliprole-resistance-related lncRNAs in C. suppressalis. It elaborates the views underlying the mechanism conferring chlorantraniliprole resistance in lncRNAs.