Abstract: 【Aim】 The aim of this study is to elucidate the effect of Nosema bombycis infection on the expression level of Bombyx Turtle (Bmtutl) gene in different tissues of larvae of the silkworm (Bombyx mori) at different time post infection, so as to lay the foundation for revealing the infection mechanism of N. bombycis. 【Methods】 The sequence characteristics of three isoforms of Bmtutl (Bmtutl-464, Bmtutl-519 and Bmtutl-810) of B. mori were analyzed by bioinformatics methods. The expression levels of Bmtutl-464, Bmtutl-519 and Bmtutl-810 in the midgut, hemolymph, and fat body of B.mori larvae infected by N. bombycis at 12, 24, 48, 72, 96 and 120 h post inoculation, respectively, were detected by qPCR. 【Results】 The secondary structures of the three Bmtutl isoforms are mainly composed of random coil, α-helix, β-turn and extended strand, and the proportion of random coil is the highest. However, PredictProtein analysis indicated that there was a large difference in protein/polynucleotide binding sites between Bmtutl-464, Bmtutl-519 and Bmtutl-810. qPCR analysis showed that the expression of Bmtutl-464, Bmtutl-519 and Bmtutl-810 in the midgut, hemolymph and fat body of B. mori larvae was inhibited after N. bombycis infection, and most significantly inhibited in the fat body. The expression of Bmtutl-519 and Bmtutl-810 in the fat body of B. mori larvae infected by N. bombycis was strongly inhibited since 72 h post inoculation, and especially the relative expression level of Bmtutl-519 in the fat body in the treatment group was less than 5.0% of that in the control. 【Conclusion】 The three isoforms of Bmtutl have different sequence characteristics. N. bombycis infection inhibits the expression of Bmtutl-464, Bmtutl-519 and Bmtutl-810 in the midgut, hemolymph and fat body of B. mori larvae, especially the expression of Bmtutl-519. These results suggest that Bmtutl-519 protein may play a major role in the process of N. bombycis infecting the silkworms as compared with the other two Bmtutl isoforms.

Key words:  Bombyx mori, Nosema bombycis, Bombyx mori Turtle protein, sequence analysis, phase expression