Using de novo transcriptome assembly and analysis to study RNAi in Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae)

Phenacoccus solenopsisis one of the major polyphagous crop pests in India. Inadequate genomic or transcriptomic resources have limited the molecular studies in this insect despite its huge economic importance. The existing molecular sequence resources of this insect were supplemented through RNA sequencing,de novotranscriptome assembly and analysis, which generated 12, 925 CDS from 23,643 contigs with an average size of 1077.5 bp per CDS and 85.1% positive BLAST hits with NCBI Non redundant (nr) database. Twenty three genes involved in RNAi machinery identified through BLASTx search against NCBI nr database suggested the existence of robust RNAi in mealybug. RNAi inP. solenopsiswas demonstrated through knockdown ofIAP(Inhibitor of Apoptosis), AQP(Aquaporin), CAL(Calcitonin), VATPase(V-type proton ATPase subunit F 1), bursicon, chitin synthase, SNF7andα-amylaseby injecting sequence specific dsRNA of respective genes in adult female. Additionally, feeding RNAi has been demonstrated in 2ndinstar nymph through dsRNA uptake in plant. The knockdown of core RNAi machinery genes such asDicer,ArgonauteandStaufensignificantly hampered RNAi efficiency in this insect. However, downregulation ofdsRNasesimproved RNAi efficiency. Sequential studies for understanding RNAi inP. solenopsisusing transcriptome sequences have also been reported. The present study provides a base for future research on developing RNAi as strategy for management of this pest.