Selection of candidate reference genes for RT-qPCR analysis in Argulus siamensis and their validation through screening of drugs and drug targets

Evaluation of reference genes for qRT-PCR studies in the colchicine producing Gloriosa superba L

The flame lily, Gloriosa superba L., is one of the two primary sources of the anti-inflammatory drug, colchicine. Previous studies have shown that a higher level of colchicine production occurs in the rhizomes than in leaves and roots. Earlier precursor feeding and transcriptome analysis of G. superba have provided a putative pathway and candidate genes involved in colchicine biosynthesis. Comparative analysis of expression levels of candidate pathway genes in different tissues of G. superba using quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) can reveal highly expressed genes in the rhizome compared to other tissues which could suggest roles of the gene products in colchicine biosynthesis. Normalization is an important step in effectively analyzing differential gene expression by qRT-PCR with broader applications. The current study selected candidate reference genes from the transcriptome datasets and analyzed them to determine the most stable genes for normalization of colchicine biosynthesis-related genes. Using RefFinder, one stable reference gene, UBC22, was selected to normalize gene expression levels of candidate methyltransferase (MT) genes in the leaves, roots, and rhizomes of G. superba. With UBC22 as reference gene, the methyltransferases, GsOMT1, GsOMT3, and GsOMT4 showed significantly higher expression levels in the rhizome of G. superba, while MT31794 was more highly expressed in the roots. In conclusion, the current results showed a viable reference gene expression analysis system that could help elucidate colchicine biosynthesis and its exploitation for increased production of the drug in G. superba.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11816-023-00840-x.

Stability evaluation and validation of appropriate reference genes for real-time PCR expression analysis of immune genes in the rohu (Labeo rohita) skin following argulosis

Argulosis is one of the most unrestrained economically significant freshwater fish ectoparasitic diseases. Proper selection or normalization of the best reference gene governs the accuracy of results of gene expression studies using real-time PCR. Earlier studies in rohu carp (Labeo rohita) have used reference genes without proper validation. Here, seven candidate reference genes viz., acidic ribosomal protein (ARP0), glyceraldehyde 3-phosphate dehydrogenase, RNA polymerase II (RPo), elongation factor1α (EF1α), α- tubulin (AT), ribosomal protein L 10, and β-actin were evaluated using four algorithms (geNorm, BestKeeper, NormFinder and ∆Ct) followed by a comprehensive gene expression analysis using skin tissue of rohu at varied time points of experimental Argulus siamensis infection. ARP0 and EF1α were found to be the most stable whereas RPo and AT were considered as least stable genes based on basal expression level and variation in expression levels. Validation of candidate reference genes was undertaken by looking into the expression of six immune-related genes using the two most stable and two least stable genes as housekeeping genes in Argulus-infected rohu skin at different time points of infection. An increased expression of immune genes indicated the role of inflammation and the immune modulation process at the site of attachment of parasites in governing infection.

An insight into the interaction between Argulus siamensis and Labeo rohita offers future therapeutic strategy to combat argulosis

Aquaculture and fisheries are salient flourishing sectors in the world but their sustainability is often afflicted by several pathogenic diseases. Among all the pathogenic diseases of fish, parasitic diseases are found to be a major cause of concern. Argulosis is one of the dominant parasitic problems encountered in Indian aquaculture practices. Argulus siamensis is the most prevalent argulid species harming the Indian major carp species including Labeo rohita. The major carps respond to parasitic infestation by elevating various immune relevant genes. The therapeutic chemicals, synthetic drugs and other plant extracts have made a progress in the fight against argulosis. However, there is no effective vaccine and drugs are available for this disease. Thus, designing efficient, cost-effective and eco-friendly control and treatment strategies for argulosis is presently needed. Keeping the aforementioned facts in mind, the current review elaborated the immunological interaction between A. siamensis and L. rohita, available combat tactics, highlighted the already identified vaccine candidates to design effective control measures and illustrated the use of omics technology in future to combat argulosis.

Antiparasitic potentiality of ethanol and methanol extracts of Azadirachta indica leaf for eggs and copepodid stage of Argulus japonicus: in vitro study

In the present study, eggs and copepodid stages of Argulus japonicus were treated with ethanol and methanol extract of Azadirachta indica (neem) leaf and its antiparasitic efficacy (AE %) was determined. The experiments were performed in triplicate along with the positive (2% DMSO) and negative (without DMSO and extract) control groups. The reduced cumulative hatching percentage of eggs by 13% (in ethanolic) and 17% (in methanolic) extract of neem leaf at 1.5 g L^-1 was obtained during 15-day exposure compared to the control group showing 70-85% eggs hatching. The AE of 100% for ethanolic and 91.66% for methanolic extract against the copepodid stage was found at 1.25 and 1.5 g L^-1 respectively in 6 h. The histological analysis of the eggs showed the undifferentiated decaying mass of cells with extensively damaged eggs when treated with ethanolic extract of neem leaf. Further, severe degeneration in the branchial region, digestive tract and eye cells was observed in the copepodids treated with ethanol extract than the methanol extract. The terpenoids a potential antiparasitic compound of ethanolic extract produced more AE than the methanolic extract. Thus, the ethanolic extract of neem leaf can be potentially utilized as a natural parasiticide to disrupt the egg and other life phases of A. japonicus.

Safety of emamectin benzoate administered in feed to Nile tilapia Oreochromis niloticus (L.)

Emamectin benzoate (EB) premix top-coated onto feed is extensively used to treat ectoparasitic crustacean infestations in aquaculture. This study evaluated the safety of EB-dosing in Nile tilapia Oreochromis niloticus at the recommended dose and dosage of 50 μg/kg biomass/day for 7 consecutive days (1X) and compared with control and 10 times the recommended dose (10X). Depletion of EB-residues in the edible muscle of 1X-dosed Nile tilapia was also studied. Mortality, behavioural changes, feed consumption, biomass, EB-residue depletion, and histopathological alterations in the kidney, liver and intestine were determined at slated intervals. Significant dose-dependent reduction in feed intake and biomass and insignificant mortalities were noted in 1X and 10X EB-dosed fish. In 1X EB-dosed fish muscle, the residues peaked on day 7 EB-dosing (9.72 ng/g) and decreased subsequently. Nevertheless, the residue levels were within the acceptable limit of the European Commission and the Canadian Food Inspection Agency even during the EB-dosing period. Histologically, tubule degeneration in the kidney, mild glycogen vacuolation in the liver, and loss of absorptive vacuoles, inflammation and disintegration of the epithelial layer in the intestine of Nile tilapia fed the 1X EB-diet were observed. The fish reverted back to their normal functions with time upon termination of oral-EB-dosing. This work contributed scientific data on the safety of EB particularly on the feed intake, growth reduction, mortality, histopathological alterations, and EB-residue levels in the edible tissues of Nile tilapia fed at the recommended dose and dosage, which suggested that EB-therapy might be reasonably risky in a tropical climate.