Biology and gene alternation studies of pink mealybug against gibberellic acid, a commonly used agrochemical in grape

Maconellicoccus hirsutus (Green) is a destructive pest of agricultural and horticultural crops. Gibberellic acid (GA3) is one of the most widely sprayed agrochemicals in the grape field, and the mealybug is often exposed to this chemical. Gene expression analyses are vital for unveiling the molecular mechanisms which regulate the xenobiotic metabolism. In this study, we did biology and gene expression study of mealybug exposed to a suboptimal dose of GA3. The lifecycle analyses revealed that Gibberellic acid (250ppm) registered longest total female life cycle with an average of 58.3 ± 0.78 days, with the highest average fecundity (264.6 ± 5.42 eggs/ovisac) compared to the sublethel doses of insecticides(buprofezin -150ppm; imidacloprid- 66ppm) control. To analyse the gene alternation, a total of six samples (3 GA3 treated and 3 control) were subjected to Illumina-based RNAseq with two replicates for each strain has been carried out and the transcriptome data has been submitted to NCBI (Bioproject Id PRJNA808162). A total of 41824 transcripts and 37492 unigenes were assembled with an average contig length of 1292.5. The BUSCO scores for the assembly is C:93.4%[S:82.4%,D:11.0%], F:1.4% (fragmented), M:5.2% (missing), n:1367 (total no of conserved genes). De novo transcriptome analysis showed the 153 unigenes were differentially expressed and the important genes belonged to the m-TOR signaling pathways, Apoptosis- fly pathways, Ubiquitin-mediated proteolysis pathways, wnt signaling pathways, and fox-O signaling pathways were highly enriched. This finding supports the possible hormesis induction by the suboptimal dose of GA3 with the changes in the biology and gene expression.