Female tick salivary glands undergo rapid degeneration several days post engorgement. This degeneration may be caused by the increased concentration of ecdysone in the hemolymph during the fast feeding period and both autophagy and apoptosis occur. In this work, we first proved ATG and Caspase gene expression peaks during degeneration of the tick salivary glands. We explored the regulatory role of Rhipicephalus haemaphysaloides autophagy related 5 (RhATG5) in the degeneration of tick salivary glands. During the fast feeding phase, RhATG5 was cleaved and both calcium concentration and the transcription of RhCalpains increased in the salivary glands. Recombinant RhATG5 was cleaved by μ-Calpain only in the presence of calcium; the mutant RhATG5^191-199Δ was not cleaved. Treatment with 20-hydroxyecdysone (20E) led to programmed cell death in the salivary glands of unfed ticks in vitro, RhATG8-phosphatidylethanolamine (PE) was upregulated in ticks treated with low concentration of 20E. Conversely, RhATG8-PE decreased and RhCaspase-7 increased in ticks treated with a high concentration of 20E and transformed autophagy to apoptosis. High concentrations of 20E led to the cleavage of RhATG5. Calcium concentration and expression of RhCalpains were also upregulated in the tick salivary glands. RNA interference (RNAi) of RhATG5 in vitro inhibited both autophagy and apoptosis of the tick salivary glands. RNAi of RhATG5 in vivo significantly inhibited the normal feeding process. These results demonstrated that high concentrations of 20E led to the cleavage of RhATG5 by increasing the concentration of calcium and stimulated the transition from autophagy to apoptosis.

中文翻译：

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ATG5有助于sal唾液腺变性期间自噬向凋亡的转变

雌性tick唾液腺在充血后几天会迅速退化。这种变性可能是由于在快速进食期间血淋巴中的蜕皮激素浓度增加而引起的，自噬和凋亡均会发生。在这项工作中，我们首先证明了TG唾液腺变性期间ATG和Caspase基因表达的峰值。我们探讨了Rhipicephalus haemaphysaloides自噬相关5（RhATG5）在of唾液腺变性中的调节作用。在快速饲喂阶段，RhATG5被切割，唾液腺中的钙浓度和RhCalpains的转录均增加。重组RhATG5仅在钙存在下被μ-Calpain切割；突变型^{RhATG5191-199Δ}没有分裂。用20-羟基蜕皮酮（20E）处理导致体外未进食tick的唾液腺程序性死亡，RhATG8-磷脂酰乙醇胺（PE）在低浓度20E处理的tick中上调。相反，在高浓度20E处理的tick中，RhATG8-PE减少，RhCaspase-7增加，并使自噬转变为凋亡。高浓度的20E导致RhATG5的裂解。the唾液腺中的钙浓度和RhCalpains的表达也被上调。RhATG5的RNA干扰（RNAi）在体外抑制the唾液腺的自噬和细胞凋亡。RhATG5的RNAi体内明显抑制了正常的饲养过程。这些结果表明高浓度的20E通过增加钙的浓度导致RhATG5的裂解，并刺激了自噬向细胞凋亡的转变。