Variation in immuno-reproductive milieu of testis in Clarias magur from pre-spawning to spawning phase: An indication towards non-canonical role of immune elements in testes.

Immune mechanisms are major players in ensuring the normal functioning of testicular functions. However, apart from their role in active defence against pathogens, prior studies have also suggested a possibility for reproduction-related (non-immune) functions of certain immune elements. This study employs a comparative transcriptomics approach followed by network analysis for tracking the variation in the immuno-reproductive milieu of Clarias magur testis in spawning versus pre-spawning phase. The results show a significant modulation of both reproduction and immune-relevant genes in spawning versus pre-spawning phase. The functional enrichment of the upregulated reproduction-relevant gene network also shows immune-related biological processes which indicates a probability of involvement of these candidates in spermatogenesis-related events for switching from pre-spawning to spawning phase. The upregulated immune network is highly dense with 40 hubs, 10 cluster sub-networks and 142 functionally enriched pathways in comparison to its downregulated counterpart with only 5 hubs, 1 cluster and 1 enriched pathway. These findings indicate that the synchronisation in modulation of both reproductive and immune-related factors is critical for progression of testicular events guiding the switch from pre-spawning to spawning phase. The reproductive phase-dependent variation in plasma sex steroid levels and the selected genes for quantitative PCR also corroborated this hypothesis. The study also serves as a preliminary screening step for probable immune candidates that may be involved in reproductive functions of testis in addition to defence.