College of Life Sciences, Shangrao Normal University, Shangrao, China; Key Laboratory of Insect Developmental and Evolutionary Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, China.
College of Life Sciences, Shangrao Normal University, Shangrao, China.
Dev Comp Immunol. 2020 Oct;111:103754. doi: 10.1016/j.dci.2020.103754. Epub 2020 May 26.
Bt protein, produced by Bacillus thuringiensis, can bind receptors to destroy the physiological functions of the insect midgut. It is unknown whether Bt can also target the hindgut and influence its defense against fecal bacteria. Here we show that Crystal protein 1Ab (Cry1Ab), a Bt protein, was detected in the larval hindgut contents of Bombyx mori after ingestion of this toxin protein. The number of fecal bacteria that can be inhibited by the hindgut prophenoloxidase-induced melanization was significantly enhanced after oral ingestion of Cry1Ab. Although the hindgut contents became brown, the activity of hindgut phenoloxidase was decreased. LC-MS/MS analysis of the hindgut lumen contents revealed that many new proteins including several proteases were newly secreted. The enhanced secretion of proteases cleaved prophenoloxidase to decrease its activity, including the corresponding activity to inhibit the fecal bacteria. In addition, after ingestion of Cry1Ab, the pylorus (between the midgut and hindgut) could not autonomously contract due to the physical detachment of the acellular cuticle-like membrane from the epidermal cells, which prevented the movement of food from the midgut to the hindgut. Some cells in the cryptonephry of the hindgut became swollen and degraded, possibly due to the presence of Cry1Ab in the hindgut. These findings demonstrate that the inhibition of feces bacteria by the hindgut prophenoloxidase-induced melanization is out of control after Cry1Ab ingestion.
苏云金芽孢杆菌产生的 Bt 蛋白可以与受体结合，破坏昆虫中肠的生理功能。目前尚不清楚 Bt 是否也能靶向后肠并影响其对粪便细菌的防御。在这里，我们发现，在摄入这种毒素蛋白后，家蚕幼虫后肠内容物中检测到了一种 Bt 蛋白——Cry1Ab。后肠原酚氧化酶诱导黑化所抑制的粪便细菌数量在口服 Cry1Ab 后显著增加。尽管后肠内容物变成棕色，但后肠酚氧化酶的活性降低。对后肠腔内容物的 LC-MS/MS 分析显示，许多新的蛋白质被新分泌，包括几种蛋白酶。蛋白酶的大量分泌可切割原酚氧化酶，从而降低其活性，包括对抑制粪便细菌的相应活性。此外，在摄入 Cry1Ab 后，由于无细胞角质层样膜与表皮细胞的物理分离，中肠和后肠之间的幽门不能自主收缩，从而阻止食物从中肠向后肠移动。后肠隐窝中的一些细胞肿胀和降解，可能是由于后肠中存在 Cry1Ab。这些发现表明，Cry1Ab 摄入后，后肠原酚氧化酶诱导的黑化对粪便细菌的抑制失去控制。
