Determination of Cry toxin activity and identification of an aminopeptidase N receptor-like gene in Asymmathetes vulcanorum (Coleoptera: Curculionidae)

Status of knowledge of the broad-nosed weevils of Colombia (Coleoptera, Curculionidae, Entiminae)

Broad-nosed weevils in the subfamily Entiminae (Coleoptera: Curculionidae) are highly diverse, not only in terms of number of species, but also in their sizes, forms and colours. There are eight tribes, 50 genera and 224 entimine species recorded from Colombia: seven genera and 142 species are considered endemic and only a handful of species, which are recognised as pests of Citrus or potatoes, are broadly known. The large diversity of this subfamily in the country is only superficially known and even though genus level identifications are generally achievable, species identification remains quite challenging, due in part to limited access to broadly-scattered basic information. Summaries of available information and bibliographic resources for each of the tribes represented in Colombia are offered, along with a checklist of the species of Entiminae recorded from the country, obtained from literature and a pictorial key for tribal recognition. New combinations are proposed for eight species of the genus Lanterius Alonso-Zarazaga & Lyal. Information on the distribution of entimine species in Colombia is compiled for the first time, including complete references to each original description and available taxonomic revisions. About a third of the species of Entiminae remain as recorded from the country without specific locality information. In addition, genus level distributional maps are presented, generated from data obtained from four Colombian entomological collections. Lastly, some challenges for entimine identification in Colombia, which likely extend throughout the Neotropical region, are briefly discussed. This contribution aims, in part, to facilitate and promote entimine research in northern South America.

Insecticidal Activity of Bacillus thuringiensis Proteins Against Coleopteran Pests

Bacillus thuringiensis is the most successful microbial insecticide agent and its proteins have been studied for many years due to its toxicity against insects mainly belonging to the orders Lepidoptera, Diptera and Coleoptera, which are pests of agro-forestry and medical-veterinary interest. However, studies on the interactions between this bacterium and the insect species classified in the order Coleoptera are more limited when compared to other insect orders. To date, 45 Cry proteins, 2 Cyt proteins, 11 Vip proteins, and 2 Sip proteins have been reported with activity against coleopteran species. A number of these proteins have been successfully used in some insecticidal formulations and in the construction of transgenic crops to provide protection against main beetle pests. In this review, we provide an update on the activity of Bt toxins against coleopteran insects, as well as specific information about the structure and mode of action of coleopteran Bt proteins.

Analysis of Homologs of Cry-toxin Receptor-Related Proteins in the Midgut of a Non-Bt Target, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae)

The brown planthopper (BPH) Nilaparvata lugens is one of the most destructive insect pests in the rice fields of Asia. Like other hemipteran insects, BPH is not susceptible to Cry toxins of Bacillus thuringiensis (Bt) or transgenic rice carrying Bt cry genes. Lack of Cry receptors in the midgut is one of the main reasons that BPH is not susceptible to the Cry toxins. The main Cry-binding proteins (CBPs) of the susceptible insects are cadherin, aminopeptidase N (APN), and alkaline phosphatase (ALP). In this study, we analyzed and validated de novo assembled transcripts from transcriptome sequencing data of BPH to identify and characterize homologs of cadherin, APN, and ALP. We then compared the cadherin-, APN-, and ALP-like proteins of BPH to previously reported CBPs to identify their homologs in BPH. The sequence analysis revealed that at least one cadherin, one APN, and two ALPs of BPH contained homologous functional domains identified from the Cry-binding cadherin, APN, and ALP, respectively. Quantitative real-time polymerase chain reaction used to verify the expression level of each putative Cry receptor homolog in the BPH midgut indicated that the CBPs homologous APN and ALP were expressed at high or medium-high levels while the cadherin was expressed at a low level. These results suggest that homologs of CBPs exist in the midgut of BPH. However, differences in key motifs of CBPs, which are functional in interacting with Cry toxins, may be responsible for insusceptibility of BPH to Cry toxins.