The potential pigmentation-related genes in spider mites revealed by comparative transcriptomes of the red form of Tetranychus urticae

Uridine Diphosphate Glycosyltransferases (UGTs) Involved in the Carotenoid-Based Body Color Difference between Tetranychus cinnabarinus (Red) and Tetranychus urticae (Green)

It has long been disputed whether Tetranychus cinnabarinus and Tetranychus urticae belong to the same genus, with T. cinnabarinus regarded as a red form of T. urticae. However, it is unclear why T. urticae and T. cinnabarinus have different body colors. Since carotenoids are responsible for the color of many organisms, the carotenoid profiles of T. cinnabarinus and T. urticae were compared by HPLC. There was no difference in carotenoid type, but T. cinnabarinus contained significantly more neoxanthin, astaxanthin, α-carotene, β-carotene, and γ-carotene, which may contribute to the deep red color. The transcriptome sequencing of both species identified 4079 differentially expressed genes (DEGs), of which 12 were related to carotenoid metabolism. RNA interference (RNAi) experiments demonstrated that silencing seven of these DEGs resulted in the different accumulation of carotenoid compounds in T. cinnabarinus and T. urticae. In addition, the body of T. urticae turned yellow after two days of feeding with UGT double-stranded RNAs and β-UGT small interfering RNAs. In conclusion, differences in the carotenoid profiles of T. urticae and T. cinnabarinus may be responsible for the different body colors.

Biology of Two-Spotted Spider Mite (Tetranychus urticae): Ultrastructure, Photosynthesis, Guanine Transcriptomics, Carotenoids and Chlorophylls Metabolism, and Decoyinine as a Potential Acaricide

Two-Spotted Spider Mites (TSSMs, Tetranychus urticae Koch 1836 (Acari: Tetranychidae)) is one of the most important pests in many crop plants, and their feeding activity is based on sucking leaf cell contents. The purpose of this study was to evaluate the interaction between TSSMs and their host Lima bean (Phaseolus lunatus) by analyzing the metabolomics of leaf pigments and the transcriptomics of TSSM guanine production. We also used epifluorescence, confocal laser scanning, and transmission electron microscopies to study the morphology and structure of TSSMs and their excreta. Finally, we evaluated the potential photosynthetic ability of TSSMs and the activity and content of Ribulose-1,5-bisphosphate Carboxylase/Oxigenase (RubisCO). We found that TSSMs express several genes involved in guanine production, including Guanosine Monophosphate Synthetase (GMPS) and decoyinine (DCY), a potential inhibitor of GMPS, was found to reduce TSSMs proliferation in infested Lima bean leaves. Despite the presence of intact chloroplasts and chlorophyll in TSSMs, we demonstrate that TSSMs do not retain any photosynthetic activity. Our results show for the first time the transcriptomics of guanine production in TSSMs and provide new insight into the catabolic activity of TSSMs on leaf chlorophyll and carotenoids. Finally, we preliminary demonstrate that DCY has an acaricidal potential against TSSMs.

Comparative transcriptome analysis of skin color-associated genes in leopard coral grouper (Plectropomus leopardus)

BACKGROUND

The leopard coral grouper (Plectropomus leopardus) is an important economic species in East Asia-Pacific countries. To meet the market demand, leopard coral grouper is facing overfishing and their population is rapidly declining. With the improvement of the artificial propagation technique, the leopard coral grouper has been successfully cultured by Fisheries Research Institute in Taiwan. However, the skin color of farmed individuals is often lacking bright redness. As such, the market price of farmed individuals is lower than wild-type.

RESULTS

To understand the genetic mechanisms of skin coloration in leopard coral grouper, we compared leopard coral grouper with different skin colors through transcriptome analysis. Six cDNA libraries generated from wild-caught leopard coral grouper with different skin colors were characterized by using the Illumina platform. Reference-guided de novo transcriptome data of leopard coral grouper obtained 24,700 transcripts, and 1,089 differentially expressed genes (DEGs) were found between red and brown skin color individuals. The results showed that nine candidate DEGs (epha2, sema6d, acsl4, slc7a5, hipk1, nol6, timp2, slc25a42, and kdf1) significantly associated with skin color were detected by using comparative transcriptome analysis and quantitative real-time polymerase chain reaction (qRT-PCR).

CONCLUSIONS

The findings may provide genetic information for further skin color research, and to boost the market price of farmed leopard coral grouper by selective breeding.