The genome and sex-dependent responses to temperature in the common yellow butterfly, Eurema hecabe.

BACKGROUND: Lepidoptera (butterflies and moths) is one of the most geographically widespread insect orders in the world, and its species play important and diverse ecological and applied roles. Climate change is one of the biggest challenges to biodiversity this century, and lepidopterans are vulnerable to climate change. Temperature-dependent gene expression differences are of relevance under the ongoing climate crisis. However, little is known about how climate affects gene expression in lepidopterans and the ecological consequences of this, particularly with respect to genes with biased expression in one of the sexes. The common yellow butterfly, Eurema hecabe (Family Pieridae), is one of the most geographically widespread lepidopterans that can be found in Asia, Africa, and Australia. Nevertheless, what temperature-dependent effects there may be and whether the effects differ between the sexes remain largely unexplored. RESULTS: Here, we generated high-quality genomic resources for E. hecabe along with transcriptomes from eight developmental stages. Male and female butterflies were subjected to varying temperatures to assess sex-specific gene expression responses through mRNA and microRNA transcriptomics. We find that there are more temperature-dependent sex-biased genes in females than males, including genes that are involved in a range of biologically important functions, highlighting potential ecological impacts of increased temperatures. Further, by considering available butterfly data on sex-biased gene expression in a comparative genomic framework, we find that the pattern of sex-biased gene expression identified in E. hecabe is highly species-specific, rather than conserved across butterfly species, suggesting that sex-biased gene expression responses to climate change are complex in butterflies. CONCLUSIONS: Our study lays the foundation for further understanding of differential responses to environmental stress in a widespread lepidopteran model and demonstrates the potential complexity of sex-specific responses of lepidopterans to climate change.

Micro-RNA Clusters Integrate Evolutionary Constraints on Expression and Target Affinities: The miR-6/5/4/286/3/309 Cluster in Drosophila.

A striking feature of micro-RNAs is that they are often clustered in the genomes of animals. The functional and evolutionary consequences of this clustering remain obscure. Here, we investigated a micro-RNA cluster miR-6/5/4/286/3/309 that is conserved across drosophilid lineages. Small RNA sequencing revealed expression of this micro-RNA cluster in Drosophila melanogaster leg discs, and conditional overexpression of the whole cluster resulted in leg appendage shortening. Transgenic overexpression lines expressing different combinations of micro-RNA cluster members were also constructed. Expression of individual micro-RNAs from the cluster resulted in a normal wild-type phenotype, but either the expression of several ancient micro-RNAs together (miR-5/4/286/3/309) or more recently evolved clustered micro-RNAs (miR-6-1/2/3) can recapitulate the phenotypes generated by the whole-cluster overexpression. Screening of transgenic fly lines revealed downregulation of leg-patterning gene cassettes in generation of the leg-shortening phenotype. Furthermore, cell transfection with different combinations of micro-RNA cluster members revealed a suite of downstream genes targeted by all cluster members, as well as complements of targets that are unique for distinct micro-RNAs. Considered together, the micro-RNA targets and the evolutionary ages of each micro-RNA in the cluster demonstrate the importance of micro-RNA clustering, where new members can reinforce and modify the selection forces on both the cluster regulation and the gene regulatory network of existing micro-RNAs. Key words: micro-RNA, cluster, evolution.

Terpenes and Terpenoids in Plants: Interactions with Environment and Insects.

The interactions of plants with environment and insects are bi-directional and dynamic. Consequently, a myriad of mechanisms has evolved to engage organisms in different types of interactions. These interactions can be mediated by allelochemicals known as volatile organic compounds (VOCs) which include volatile terpenes (VTs). The emission of VTs provides a way for plants to communicate with the environment, including neighboring plants, beneficiaries (e.g., pollinators, seed dispersers), predators, parasitoids, and herbivores, by sending enticing or deterring signals. Understanding terpenoid distribution, biogenesis, and function provides an opportunity for the design and implementation of effective and efficient environmental calamity and pest management strategies. This review provides an overview of plant-environment and plant-insect interactions in the context of terpenes and terpenoids as important chemical mediators of these abiotic and biotic interactions.

Infection patterns of dengue, Zika and endosymbiont Wolbachia in the mosquito Aedes albopictus in Hong Kong.

BACKGROUND: The mosquito Aedes albopictus is a vector of dengue and Zika viruses. Insecticide-resistant mosquito populations have evolved in recent decades, suggesting that new control strategies are needed. Hong Kong has a monsoon-influenced humid subtropical climate, which favours the spread of mosquitoes. However, baseline information on the composition and dynamics of the occurrence of endosymbiont Wolbachia in local Ae. albopictus is lacking, hindering the development of scientifically-informed control measures. This study identifies the presence and absence of dengue and Zika viruses, and Wolbachia infection in Aedes albopictus in Hong Kong. METHODS: Oviposition traps were set at 57 areas in Hong Kong, and both immature and adult mosquitoes were collected on a monthly basis between April 2018 and April 2019 as the study sample. Each individual mosquito in this sample was processed and screened for the presence of the dengue and Zika viruses and the endosymbionts Wolbachia wAlbA and wAlbB with PCR. RESULTS: Totals of 967 and 984 mosquitoes were tested respectively for the presence of dengue and Zika viruses, and no trace of either infection was found in these samples. The presence of wAlbA and wAlbB was also tested in 1582 individuals. Over 80% of these individuals were found to be stably infected with Wolbachia throughout the thirteen-month collection period (~ 47% singly-infected; ~ 36.8% doubly infected with both wAlbA and wAlbB). CONCLUSIONS: The high degree of Wolbachia wAlbA and wAlbB infection in Ae. albopictus mosquitoes in Hong Kong, coupled with the absence of any signs of infection by dengue and Zika viruses, contrasts significantly with the pattern of mosquito infection in other parts of Asia. Further studies of the infection pattern in local mosquitoes are warranted before mosquito control strategies used in other regions are implemented in Hong Kong.