Starvation-Induced Calcium Dysregulation Is Associated with Autophagy, Apoptosis, and Posterior Silk Gland Injury in Bombyx mori

The silkworm (Bombyx mori) is a key economic insect in sericulture, and silk production relies on nutrition and posterior silk gland (PSG) development. Nutritional deficiency impairs silk protein synthesis and secretion in the silkworm PSG, potentially affecting silk yield and quality. In this study, we investigated the cellular and molecular changes associated with starvation-induced injury in the PSG. Starvation impaired PSG development and altered NADPH levels, accompanied by increased dihydroethidium (DHE) fluorescence, elevated glutathione S-transferase (GST) activity, increased superoxide dismutase (SOD) activity at 24 and 48 h, and increased BmCAT transcript abundance. Transmission electron microscopy (TEM) revealed that short-term starvation was associated with the accumulation of autophagic structures, including double-membrane autophagosomes and autolysosomes. By contrast, prolonged starvation resulted in severe ultrastructural damage, characterized by nuclear envelope disruption and chromatin condensation. Furthermore, reverse transcription quantitative PCR (RT-qPCR) and Western blotting revealed increased expression of autophagy-related markers and apoptosis-associated changes, including cleaved caspase-3 accumulation after 72 h of starvation. Notably, prolonged starvation was accompanied by increased intracellular Ca2+ levels and elevated NtATG5 abundance, suggesting that altered Ca2+ homeostasis may be associated with the apoptosis-associated responses observed in the PSG. Together, these findings identify coordinated changes in redox status, Ca2+ homeostasis, and autophagy- and apoptosis-associated markers during starvation-induced PSG injury, providing a basis for further mechanistic studies and evaluation of food deprivation in sericulture.