The whitefly Bemisia tabaci is an important agricultural pest with global distribution. This phloem-sap feeder harbors a primary symbiont, “Candidatus Portiera aleyrodidarum”, which compensates for the deficient nutritional composition of its food sources, and a variety of secondary symbionts. Interestingly, all of these secondary symbionts are found in co-localization with the primary symbiont within the same bacteriocytes, which should favor the evolution of strong interactions between symbionts. In this paper, we analyzed the genome sequences of the primary symbiont Portiera and of the secondary symbiont Hamiltonella in the B. tabaci Mediterranean (MED) species in order to gain insight into the metabolic role of each symbiont in the biology of their host. The genome sequences of the uncultured symbionts Portiera and Hamiltonella were obtained from one single bacteriocyte of MED B. tabaci. As already reported, the genome of Portiera is highly reduced (357 kb), but has kept a number of genes encoding most essential amino-acids and carotenoids. On the other hand, Portiera lacks almost all the genes involved in the synthesis of vitamins and cofactors. Moreover, some pathways are incomplete, notably those involved in the synthesis of some essential amino-acids. Interestingly, the genome of Hamiltonella revealed that this secondary symbiont can not only provide vitamins and cofactors, but also complete the missing steps of some of the pathways of Portiera. In addition, some critical amino-acid biosynthetic genes are missing in the two symbiotic genomes, but analysis of whitefly transcriptome suggests that the missing steps may be performed by the whitefly itself or its microbiota. These data suggest that Portiera and Hamiltonella are not only complementary but could also be mutually dependent to provide a full complement of nutrients to their host. Altogether, these results illustrate how functional redundancies can lead to gene losses in the genomes of the different symbiotic partners, reinforcing their inter-dependency.

Jumonji C (JmjC) domain-containing proteins are a group of functionally conserved histone lysine demethylases in Eukaryotes. Growing evidences have shown that JmjCs epigenetically regulate various biological processes in plants. However, their roles in plant biotic stress, especially in rice bacterial blight resistance have been barely studied so far. In this study, we found that the global di- and tri-methylation levels on multiple lysine sites of histone three were dramatically altered after being infected by bacterial blight pathogen Xanthomonas oryzae pv. oryzae (Xoo). Xoo infection induced the transcription of 15 JmjCs, suggesting these JmjCs are involved in rice bacterial blight defense. Further functional characterization of JmjC mutants revealed that JMJ704 is a positive regulator of rice bacterial blight resistance as the jmj704 became more susceptible to Xoo than the wild-type. In jmj704, the H3K4me2/3 levels were significantly increased; suggesting JMJ704 may be involved in H3K4me2/3 demethylation. Moreover, JMJ704 suppressed the transcription of the rice defense negative regulator genes, such as NRR, OsWRKY62 and Os-11N3, by reducing the activation marks H3K4me2/3 on them. JMJ704 may be a universal switch controlling multiple genes of the bacterial blight resistance pathway. JMJ704 positively regulates rice defense by epigenetically suppressing master negative defense regulators, presenting a novel mechanism distinct from its homolog JMJ705 which also positively regulates rice defense but via activating positive defense regulators.

Four strains of the Q biotype and one of the B biotype of the whitefly Bemisia tabaci collected from China were characterised for resistance to four neonicotinoid insecticides and pymetrozine. Q biotype strains showed moderate to strong resistance to imidacloprid, thiamethoxam and acetamiprid, but little or no cross-resistance to dinotefuron. Resistance to neonicotinoids was consistently associated with resistance to pymetrozine, despite the latter having a distinct (though unresolved) mode of action. The single B biotype strain proved largely susceptible to all the insecticides investigated. Resistance in the Q biotype strains was associated with over-expression of a cytochrome P450 monooxygenase gene, CYP6CM1, whose substrate specificity presumably accounts for the observed cross-resistance profiles

The tobacco whitefly, Bemisia tabaci (Gennadius), causes severe crop losses in many agricultural systems. The worst of these losses are often associated with the invasion and establishment of specific whitefly biotypes. In a comprehensive survey of biotypes present in central China between 2005 and 2007, we obtained 191 samples of B. tabaci from 19 districts in Hubei province and its surrounds. Biotypes were identified by RAPD-PCR and by sequencing the mitochondrial cytochrome oxidase I gene (mtCO1). We determined that these central Chinese haplotypes included the world's two most invasive B. tabaci biotypes (B and Q) and two indigenous biotypes (ZHJ1 and ZHJ3). The B biotype shared >99.7% identity with other Chinese B biotypes and the Q biotype shared >99.5% of its identity with Q samples from the Mediterranean, USA, Africa and East Asia. By 2007, the Q biotype was dominant over much of Hubei province and appeared to be supplanting all other biotypes, although both the invasive and indigenous biotypes existed in sympatry in some regions. The invasion and rapid establishment of the Q biotype in China mirrors events elsewhere in the world, and we suggest that this is a consequence of its reproductive isolation, its polyphagous nature and its broad-spectrum resistance to insecticides. Its dominance has severe implications for the sustainability of some insecticide groups and for the production of a number of crops.

Spodoptera frugiperda is a serious invasive pest, which has attracted attention globally in recent years. Research on the sublethal effects of common insecticides on S. frugiperda is important for its comprehensive management in the field. In this paper, the sublethal effects have been studied for S. frugiperda exposed to the LC₃₀ concentration of three insecticides, chlorantraniliprole, dinotefuran, and beta-cypermethrin. The results showed that the pupation rates of the treatment groups were significantly lower than that of control group, but there were no significant differences in the eclosion rate. Chlorantraniliprole and beta-cypermethrin significantly inhibited fecundity of the F₀ and F₁ generations, and the number of eggs laid per female decreased by 67.4% and 43.1%, respectively, and that of the F₁ generation decreased by 28.0% and 21.7%, respectively. The intrinsic growth rate (r_m), net growth rate (R₀), and weekly growth rate (λ) of the F₀ generation in the chlorantraniliprole and beta-cypermethrin treatment groups were significantly lower than those in the control group. Additionally, dinotefuran had a certain role in promoting oviposition in the F₀ and F₁ generations, which may stimulate the growth of offspring population and cause the resurgence of pests. The results provide a reference for the effective implementation of the IPM plan in the field to control S. frugiperda.