A female-specific odorant receptor mediates oviposition deterrence in the moth Helicoverpa armigera

Presence of low-energy chlorophylls d in photosystem I trimer and monomer cores isolated from Acaryochloris sp. NBRC 102871

Acaryochloris species belong to a special category of cyanobacteria possessing chlorophyll (Chl) d. One of the photosynthetic characteristics of Acaryochloris marina MBIC11017 is that the absorption spectra of photosystem I (PSI) showed almost no bands and shoulders of low-energy Chls d over 740 nm. In contrast, the absorption spectra of other Acaryochloris species showed a shoulder around 740 nm, suggesting that low-energy Chls d within PSI are diversified among Acaryochloris species. In this study, we purified PSI trimer and monomer cores from Acaryochloris sp. NBRC 102871 and examined their protein and pigment compositions and spectral properties. The protein bands and pigment compositions of the PSI trimer and monomer of NBRC102871 were virtually identical to those of MBIC11017. The absorption spectra of the NBRC102871 PSIs exhibited a shoulder around 740 nm, whereas the fluorescence spectra of PSI trimer and monomer displayed maximum peaks at 754 and 767 nm, respectively. These spectral properties were different from those of MBIC11017, indicating the presence of low-energy Chls d within the NBRC102871 PSIs. Moreover, we analyzed the NBRC102871 genome to identify amino acid sequences of PSI proteins and compared them with those of the A. marina MBIC11017 and MBIC10699 strains whose genomes are available. The results showed that some of the sequences in NBRC102871 were distinct from those in MBIC11017 and MBIC10699. These findings provide insights into the variety of low-energy Chls d with respect to the protein environments of PSI cores among the three Acaryochloris strains.

Genome-Wide Identification, Evolution, and Female-Biased Expression Analysis of Odorant Receptors in Tuta absoluta (Lepidoptera: Gelechiidae)

The tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae), is a highly destructive invasive pest targeting Solanaceae crops. Its olfactory system plays a crucial role in host location, mate finding, and other behavioral activities. However, there is a notable gap in the literature regarding the characterization of its chemosensory genes. In this study, we conducted a genome-wide identification of 58 odorant receptors (ORs) of T. absoluta. The identified ORs exhibit coding sequence (CDS) lengths ranging from 1062 bp to 1419 bp, encoding proteins of 354 to 473 amino acids. Gene structure analysis showed that the majority of these ORs consist of five, seven, eight, or nine exons, collectively representing 67% of the total ORs identified. Through chromosomal mapping, we identified several tandemly duplicate genes, including TabsOR12a, TabsOR12b, TabsOR12c, TabsOR21a, TabsOR21b, TabsOR34a, TabsOR34b, TabsOR34c, TabsOR62a, and TabsOR62b. The phylogenetic analysis indicated that six TabsORs were clustered within the lepidopteran sex pheromone receptor clade, while an expansion clade containing ten TabsORs resulted from tandem duplication events. Additionally, five TabsORs were classified into a specific OR clade in T. absoluta. Furthermore, through RNA-Seq and RT-qPCR analyses, we identified five TabsORs (TabsOR21a, TabsOR26a, TabsOR34a, TabsOR34c, and TabsOR36) exhibiting female-antennae-biased expression. Our study provides a valuable foundation to further investigations into the molecular and ecological functions of TabsORs, particularly in relation to oviposition behavior. These findings provide foundational data for the future exploration of the functions of female-biased expression OR genes in T. absoluta, thereby facilitating the further development of eco-friendly attract-and-kill techniques for the prevention and control of T. absoluta.

Candidate membrane protein gene families related to chemoreception in a wood-boring beetle, Pharsalia antennata Gahan (Coleoptera: Cerambycidae)

The longhorned beetles are key players for the maintenance of biodiversity in the terrestrial ecosystem. As xylophagous cerambycid insects in Coleoptera, the beetles have evolved specialized olfactory and gustatory systems to recognize chemical cues in the surrounding habitats. Despite over 36,000 described species in the Cerambycidae family including a wood-boring pest Pharsalia antennata, only a limited number of them (<1 %) have been characterized regarding their chemical ecology at the molecular level. Here, we surveyed four membrane protein gene families in P. antennata related to chemoreception through transcriptomics, phylogenetics and expression profiling analyses. In total, 144 genes encoding 72 odorant receptors (ORs), 33 gustatory receptors (GRs), 23 ionotropic receptors (IRs), four sensory neuron membrane proteins (SNMPs) and 12 ionotropic glutamate receptors (iGluRs) were harvested from the transcriptome of multiple tissues including antennae and legs of both sexes. The lineage-specific expansion of PantORs possibly implied a diverse range of host plants in this beetle, supporting this correlation between the host range and olfactory receptor repertoire sizes across cerambycid species. Further phylogenetic analysis revealed that Group 2 was contributed mainly to the large OR gene repertoire in P. antennata, representing 18 genes in Group 2A and eight in Group 2B. On the other hand, some key chemosensory genes were identified by applying a phylogenetics approach, such as PantOR21 close to the 2-phenylethanol receptor in Megacyllene caryae, three carbon dioxide GRs and seven Antennal IRs (A-IRs) clades. We also determined sex- and tissue-specific expression profiles of 69 chemosensory genes, revealing the high expression of most PantORs in antennae. Noticeably, 10 sex-biased genes (six PantORs, three PantIRs and PantSNMP1a) were presented in antennae, five sex-biased PantGRs in legs and 39 sex-biased genes (15 PantORs, 13 PantGRs, eight PantIRs and three PantSNMPs) in abdomens. These findings have greatly enhanced our knowledge about the chemical ecology of P. antennata and identify candidate molecular targets for mediating smell and taste of this beetle.

Selection and Validation of Reference Genes for Gene Expression in Bactericera gobica Loginova under Different Insecticide Stresses

Insecticide resistance has long been a problem in crop pest control. Bactericera gobica is a major pest on the well-known medicinal plants Lycium barbarum L. Investigating insecticide resistance mechanisms of B. gobica will help to identify pesticide reduction strategies to control the pest. Gene expression normalization by RT-qPCR requires the selection and validation of appropriate reference genes (RGs). Here, 15 candidate RGs were selected from transcriptome data of B. gobica. Their expression stability was evaluated with five algorithms (Delta Ct, GeNorm, Normfinder, BestKeeper and RefFinder) for sample types differing in response to five insecticide stresses and in four other experimental conditions. Our results indicated that the RGs RPL10 + RPS15 for Imidacloprid and Abamectin; RPL10 + AK for Thiamethoxam; RPL32 + RPL10 for λ-cyhalothrin; RPL10 + RPL8 for Matrine; and EF2 + RPL32 under different insecticide stresses were the most suitable RGs for RT-qPCR normalization. EF1α + RPL8, EF1α + β-actin, β-actin + EF2 and β-actin + RPS15 were the optimal combination of RGs under odor stimulation, temperature, developmental stages and both sexes, respectively. Overall, EF2 and RPL8 were the two most stable RGs in all conditions, while α-TUB and RPL32 were the least stable RGs. The corresponding suitable RGs and one unstable RG were used to normalize a target cytochrome P450 CYP6a1 gene between adult and nymph stages and under imidacloprid stress. The results of CYP6a1 expression were consistent with transcriptome data. This study is the first research on the most stable RG selection in B. gobica nymphs exposed to different insecticides, which will contribute to further research on insecticide resistance mechanisms in B. gobica.

Insect neurobiology: Oviposition crowd control

A new study examines how Helicoverpa armigera females detect chemicals released by conspecific eggs in order to avoid laying more eggs on the same substrate. This work opens new avenues for basic research inquiries and offers a potential strategy for controlling insect pests.