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Rice blast, caused by the fungal pathogen Magnaporthe grisea, is one of the most devastating diseases in rice worldwide. The dominant resistance gene, Pi-d2 [previously named Pi-d(t)2], present in the rice variety Digu, confers gene-for-gene resistance to the Chinese blast strain, ZB15. Pi-d2 was previously mapped close to the centromere of chromosome 6. In this study, the Pi-d2 gene was isolated by a map-based cloning strategy. Pi-d2 encodes a receptor-like kinase protein with a predicted extracellular domain of a bulb-type mannose specific binding lectin (B-lectin) and an intracellular serine-threonine kinase domain. Pi-d2 is a single-copy gene that is constitutively expressed in the rice variety Digu. Transgenic plants carrying the Pi-d2 transgene confer race-specific resistance to the M. grisea strain, ZB15. The Pi-d2 protein is plasma membrane localized. A single amino acid difference at position 441 of Pi-d2 distinguishes resistant and susceptible alleles of rice blast resistance gene Pi-d2. Because of its novel extracellular domain, Pi-d2 represents a new class of plant resistance genes.

Genome tiling microarray studies have consistently documented rich transcriptional activity beyond the annotated genes. However, systematic characterization and transcriptional profiling of the putative novel transcripts on the genome scale are still lacking. We report here the identification of 25,352 and 27,744 transcriptionally active regions (TARs) not encoded by annotated exons in the rice (Oryza. sativa) subspecies japonica and indica, respectively. The non-exonic TARs account for approximately two thirds of the total TARs detected by tiling arrays and represent transcripts likely conserved between japonica and indica. Transcription of 21,018 (83%) japonica non-exonic TARs was verified through expression profiling in 10 tissue types using a re-array in which annotated genes and TARs were each represented by five independent probes. Subsequent analyses indicate that about 80% of the japonica TARs that were not assigned to annotated exons can be assigned to various putatively functional or structural elements of the rice genome, including splice variants, uncharacterized portions of incompletely annotated genes, antisense transcripts, duplicated gene fragments, and potential non-coding RNAs. These results provide a systematic characterization of non-exonic transcripts in rice and thus expand the current view of the complexity and dynamics of the rice transcriptome.

To obtain accurate and reliable results from quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) analysis, it is necessary to select suitable reference genes as standards for normalizing target gene expression data. QRT-PCR is a popular analytical methodology for studying gene expression and it has been used widely in studies of Aphis gossypii Glover in recent years. However, there is absence of study on the stability of the expression of reference genes in A. gossypii. In this study, eight commonly used candidate reference genes, including 18S, 28S, β-ACT, GAPDH, EF1α, RPL7, α-TUB, and TBP, were evaluated under various experimental conditions to assess their suitability for use in the normalization of qRT-PCR data. The optimal number of reference genes was determined using the geNorm program, and the suitability of particular reference genes was empirically validated by performing normalizations of expression data for the HSP70 gene. The results showed the most suitable combinations of reference genes for the different experimental conditions. For experiments based on divergent developmental stages, EF1α, β-ACT, and RPL7 are the optimal reference gene combination, both EF1α and β-ACT are the optimal combination used in the experiments of different geographical populations, whereas for experiments of the temperature changes, the combination of GAPDH and RPL7 is optimal, both 18S and β-ACT are an optimal combination for feeding assay experiments. These research results should be useful for the selection of the suitable reference genes to obtain reliable qRT-PCR data in the gene expression study of A. gossypii.

Sulfoxaflor is a novel insecticide belonging to sulfoximine chemical class that can be used to control sap-feeding insects, notably Aphis gossypii Glover. In addition to its acute toxicity, it is also important to consider the possible sublethal effects when establishing a comprehensive understanding of the toxicity of a new insecticide. We assessed the effects of a low lethal concentration (LC) of sulfoxaflor on biological parameters of A. gossypii adults (F0) and subsequent transgenerational effects, i.e., on the progeny (F1 generation). The data were analyzed using an age-stage life table procedure. The results showed that the longevity and fecundity were not significantly affected by the LC of sulfoxaflor in the F0 or F1 generations. In addition, no significant differences were observed on the developmental time of each instar, the adult pre-oviposition period, and on the longevity of F1 individuals. However, the duration of their pre-adult stage and total pre-oviposition period, as well as their mean generation time were significantly increased. These observed effects affected aphid demographic traits; the survival rate, the intrinsic rate of increase (r ), the finite rate of increase (λ), the net reproductive rate (R), and the gross reproduction rate (GRR) of the F1 individuals (i.e., from F0 mothers) were significantly lower compared to the control. Our results showed that sublethal effects of sulfoxaflor significantly slowed down A. gossypii population growth; they indicated that effects of sulfoxaflor might be increased (beyond lethal effect) through sublethal effects when concentrations decreased in sulfoxaflor-treated areas after initial application in field.

The mutation M918 L in the voltage-gated sodium channel along with detoxifying metabolism was contributed to the pyrethroid resistance in the field populations of Aphis gossypii from cotton growing regions of China. And insecticides with different modes of action should be recommended for the control of A. gossypii in the future. © 2017 Society of Chemical Industry.

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BACKGROUND The cotton aphid Aphis gossypii Glover is one of the most destructive insect pests. It has evolved resistance to numerous insecticides around the world due to the application of insecticides. Uridine diphosphate (UDP)‐glycosyltransferases (UGTs) have been reported to potentially facilitate the detoxification process of imidacloprid and thiamethoxam in A. gossypii. RESULTS In this study, the field populations of A. gossypii developed different levels of resistance to multiple insecticides. A UGT inhibitor, 5‐nitrouracil, dramatically increased the toxicity of acetamiprid in resistant populations, moderately increased the toxicity of sulfoxaflor in the imidacloprid susceptible (IMI_S) population, and populations from Yuncheng in Shanxi Province (SXYC) and Jingzhou in Hubei Province (HBJZ), and increased the toxicity of bifenthrin in the IMI_S and HBJZ populations, but there was no synergism on omethoate or carbosulfan. Quantitative real‐time PCR analysis revealed that UGT344B4 and UGT344C7 were overexpressed in all field populations, and UGT344N4 was overexpressed in the SDBZ and HBZJ populations. Furthermore, the suppression of UGT344B4 or UGT344C7 by RNA interference significantly increased the susceptibility to bifenthrin in the IMI_S population and the susceptibility to sulfoxaflor in the SXYC population. CONCLUSION These results suggested that UGTs are potentially involved in the detoxification of neonicotinoid, sulfoximine, and pyrethroid insecticides in A. gossypii. Furthermore, the overexpression of UGTs could be associated with insecticide resistance in field populations of A. gossypii. The results might be helpful for the management of insecticide resistance in field populations of A. gossypii. © 2019 Society of Chemical Industry