KNOCKDOWN OF THE IONOTROPIC γ‐AMINOBUTYRIC ACID RECEPTOR (GABAR) RDL GENE DECREASES FIPRONIL SUSCEPTIBILITY OF THE SMALL BROWN PLANTHOPPER, Laodelphax striatellus (HEMIPTERA: DELPHACIDAE)

Abstract

Insect γ-aminobutyric acid receptors (GABARs) are important molecular targets of cyclodiene and phenylpyrazole insecticides. Previously GABARs encoding rdl (resistant to dieldrin) genes responsible for dieldrin and fipronil resistance were identified in various economically important insect pests. In this study, we cloned the open reading frame cDNA sequence of rdl gene from fipronil-susceptible and fipronil-resistant strains of Laodelphax striatellus (Lsrdl). Sequence analysis confirmed the presence of a previously identified resistance-conferring mutation. Different alternative splicing variants of Lsrdl were noted. Injection of dsLsrdl reduced the mRNA abundance of Lsrdl by 27-82%, and greatly decreased fipronil-induced mortality of individuals from both susceptible and resistant strains. These data indicate that Lsrdl encodes a functional RDL subunit that mediates susceptibility to fipronil. Additionally, temporal and spatial expression analysis showed that Lsrdl was expressed at higher levels in eggs, fifth-instar nymphs, and female adults than in third-instar and fourth-instar nymphs. Lsrdl was predominantly expressed in the heads of 2-day-old female adults. All these results provide useful background knowledge for better understanding of fipronil resistance related ionotropic GABA receptor rdl gene expressed variants and potential functional differences in insects.

Cross‐resistance to three phenylpyrazole insecticides and A2′N mutation detection of GABA receptor subunit in fipronil‐resistant Laodelphax striatellus (Hemiptera: Delphacidae)

“…They have caused huge economic losses and developed resistance to multiple insecticides, as mentioned earlier. In recent years, many studies have focused on the fipronil and ethiprole resistance mechanisms of rice planthoppers, which mainly involve various types of detoxification such as esterase and P450 monooxygenases, and RDL GABA receptor mutation such as A302S and R300Q in BPH and A2′N in WBPH and SBPH . All these factors accelerated the development of resistance to fipronil.…”

“…Blank controls using sterile ultrapure water instead of the cDNA template were performed. β‐ actin was used as the internal reference gene . The primers used for qPCR are shown in Table .…”

“…However, after decades of intensive use, many target pests have developed higher resistance to fipronil, with mechanisms of increasing detoxification enzymes and target‐site cross‐resistance to cyclodiene insecticides owing to mutations of A2′S, A2′G and/or T3′M of RDL GABA receptors . More recently, an A2′N mutation of the same position subunit has been found to confer fipronil resistance in two planthopper species, the white‐backed planthopper (WBPH), Sogatella furcifera , and SBPH . Owing in part to its high toxicity to honeybee and aquatic crustaceans, China placed heavy restrictions on the use of fipronil, starting in 2009, and the European Union followed suit in 2013…”

“…Based on previous research, the A2′N mutant RDL GABA receptor plays a key role in the resistance of SBPH to fipronil, and therefore a mutation detection method must be established. The allele‐specific polymerase chain reaction (AS‐PCR), also known as PCR amplification of specific alleles (PASA) or the amplification refractory mutation system (ARMS), is a PCR‐based technology that can be applied to detect the known single nucleotide polymorphism (SNP) .…”

Transcription activity of genes taking part in Colorado potato beetle diapause regulation and its changes under the fipronil impact

“…Эта ре-акция характерна не только для фипронила. Показано, что и другие ксенобиотики также связываются с субъ-единицей рецептора, снижая уровень экспрессии как у насекомых, так и у теплокровных [23]. В частности, установлено, что у Anopheles gambiae эта субъединица является мишенью также для пиретроидов и неоникоти-ноидов [24], а кроме того, отмечено связывание с этим аллостерическим сайтом как у насекомых, так и у тепло-кровных барбитуратов и стероидов [14,25].…”