Contamination of insect DNA for RAPD-PCR analysis can be a problem because many primers are non-specific and DNA from parasites or gut contents may be simultaneously extracted along with that of the insect. We measured the quantity of food ingested and assimilated by two sympatric populations of brown planthopper (BPH), Nilaparvata lugens, one from rice and the other from Leersia hexandra (Poaceae), a wetland forage grass, and we also investigated whether host plant DNA contaminates that of herbivore insects in extractions of whole insects. Ingestion and assimilation of food were reduced significantly when individuals derived from one host plant were caged on the other species. The bands, OPA3 (1.25), OPD3 (1.10), OPD3 (0.80), OPD3 (0.60), pUC/M13F (0.35), pUC/M13F (0.20), BOXAIR (0.50), peh#3 (0.50), and peh#3 (0.17) were found in both rice-infesting populations of brown planthopper and its host plant (rice). Similarly, the bands, OPA4 (1.00), OPB10 (0.70), OPD3 (0.90), OPD3 (0.80), OPD3 (0.60), pUC/ M13F (0.35), pUC/M13F (0.20), and BOXAIR (0.50) were found in both Leersia-infesting populations of brown planthopper and the host plant. So, it is clear that the DNA bands amplified in the host plants were also found in the extracts from the insects feeding on them.
Vibriosis is a prevalent aquatic disease caused by Vibrio species and has led to massive loss of brown-marbled grouper, Epinephelus fuscoguttatus. The complexity of molecular mechanisms associated with immune defence can be studied through transcriptomics analysis. High quality and quantity of total RNAs are crucial for the veracity of RNA sequencing and gene expression analysis. A low quality RNA will compromise downstream analysis, resulting in loss of time and revenue to re-acquire the data again. Thus, a reliable and an efficient RNA isolation method is the first and most important step to obtain high quality RNA for gene expression studies. There are many aspects need to be considered when deciding an extraction method, such as the cost-effectiveness of the protocol, the duration of chemical exposure, the duration required for a complete extraction and the number of sample-transferring. A good RNA extraction protocol must be able to produce high yield and purity of RNA free from enzyme inhibitors, such as nucleases (RNase), phenols, alcohols or other chemicals carryover, apart from protein and genomic DNA contamination, to maintain isolated RNA integrity in storage condition. In this study, TransZolTM Up produced clean and pure RNA samples from control gills only but not from the infected gill and whole-body tissues. Modified conventional CTAB (conventional hexadecyltrimethylammonium bromide) method was then used as an alternative method to isolate RNA from gill and whole-body tissues of Vibrio-infected E. fuscoguttatus. Modified CTAB method produced intact RNA on gel electrophoresis with higher RIN number (>6.5) for infected gill and whole-body tissues, suggesting that this method could also be used to isolate high quality RNA from fish samples. Therefore, this method is potentially suitable to be used to extract RNA from other fish species especially those that have been infected.