Transcriptomic analysis of Bombyx mori in its early larval stage (2nd instar) of development upon Nosema bombycis transovarial infection

[Display omitted] •N. bombycis infection affects the physiology, development and immunity of B. mori.•Nosema altered expression of host genes, of which 1888 genes were significant.•Cecropins, DUOX and PIRK play a vital role in regulating the IMD pathway.•Nosema infection downregulates PPAE gene and suppress the synthesis of eumelanin. The infection caused by Nosema bombycis often known as pebrine, is a devastating sericulture disease. The infection can be transmitted to the next generation through eggs laid by infected female Bombyx mori moths (transovarial) as well as with N. bombycis contaminated food (horizontal). Most diagnoses were carried out in the advanced stages of infection until the time that infection might spread to other healthy insects. Hence, early diagnosis of pebrine is of utmost importance to quarantine infected larvae from uninfected silkworm batches and stop further spread of the infection. The findings of our study provide an insight into how the silkworm larval host defence system was activated against early N. bombycis transovarial infection. The results obtained from transcriptome analysis of infected 2nd instar larvae revealed significant (adjusted P-value