Chromosome-level genome assembly of the western flower thrips Frankliniella occidentalis.

The western flower thrips Frankliniella occidentalis (Thysanoptera: Thripidae) is a global invasive species that causes increasing damage by direct feeding on crops and transmission of plant viruses. Here, we assemble a previously published scaffold-level genome into a chromosomal level using Hi-C sequencing technology. The assembled genome has a size of 302.58 Mb, with a contig N50 of 1533 bp, scaffold N50 of 19.071 Mb, and BUSCO completeness of 97.8%. All contigs are anchored on 15 chromosomes. A total of 16,312 protein-coding genes are annotated in the genome with a BUSCO completeness of 95.2%. The genome contains 492 non-coding RNA, and 0.41% of interspersed repeats. In conclusion, this high-quality genome provides a convenient and high-quality resource for understanding the ecology, genetics, and evolution of thrips.

A chromosome-level genome for the flower thrips Frankliniella intonsa.

The flower thrips Frankliniella intonsa (Thysanoptera: Thripidae) is a common insect found in flowers of many plants. Sometimes, F. intonsa causes damage to crops through direct feeding and transmission of plant viruses. Here, we assembled a chromosomal level genome of F. intonsa using the Illumina, Oxford Nanopore (ONT), and Hi-C technologies. The assembled genome had a size of 209.09 Mb, with a contig N50 of 997 bp, scaffold N50 of 13.415 Mb, and BUSCO completeness of 92.5%. The assembled contigs were anchored on 15 chromosomes. A set of 14,109 protein-coding genes were annotated in the genome with a BUSCO completeness of 95.0%. The genome contained 491 non-coding RNA and 0.57% of interspersed repeats. This high-quality genome provides a valuable resource for understanding the ecology, genetics, and evolution of F. intonsa, as well as for controlling thrips pests.

Spinosad resistance of melon thrips, Thrips palmi, is conferred by G275E mutation in α6 subunit of nicotinic acetylcholine receptor and cytochrome P450 detoxification.

To examine the resistance mechanisms of Thrips palmi against spinosad, we cloned partial nucleotide sequences of the nicotinic acetylcholine receptor α6 subunit (TPα6) gene from susceptible (OK) and resistant (TS1 and TS5) strains and compared the deduced amino acid sequences among the three strains. The OK, TS1, and TS5 strains respectively showed LC50 values of 3.4mg/L, 2838.5mg/L, and 6655.5mg/L. The deduced amino acid sequence of TPα6 gene showed 96% identity with that of Frankliniella occidentalis. Comparison of the deduced amino acid sequences of TPα6 gene among the three strains showed that the TS1 and TS5 strains had a resistant amino acid, Glu, at amino acid position 275. On the other hand, a susceptible amino acid, Gly, was encoded at the corresponding amino acid position for the OK strain. The synergist, piperonyl butoxide, respectively caused 1.1-fold , 5.8-fold , and 9.0-fold decreases in the resistance ratios of the OK, TS1, and TS5 strains. These results suggest that spinosad resistance of T. palmi is conferred by reduced sensitivity of TPα6 and cytochrome P450-mediated detoxification.

Genomic analyses of sodium channel α-subunit genes from strains of melon thrips, Thrips palmi, with different sensitivities to cypermethrin.

We examined the genomic organization of the sodium channel α-subunit gene in two strains of melon thrips, Thrips palmi, having differing sensitivity to cypermethrin. The nucleotide sequences of the strains included 18 or 16 putative exons which covered the entire coding region of the gene producing 2039 amino acid residues. Deduced amino acid sequences of both strains showed 80% homology with those of Periplaneta americana and Cimex lectularius. Comparison of deduced amino acid sequences of both strains showed no consistent amino acid difference. In addition to the previously reported resistant amino acid (Ile) at the T929I site, both strains encoded another resistant amino acids at two positions which are involved in pyrethroid resistance in other arthropods. These amino acids might also involve in the basal levels of resistance to pyrethroids of both strains.