Silk fibroin filaments are natural proteins produced by silkworm, Bombyx mori, which is bounded by sericin polymers in silk thread used in the cocoon. Fibroin gene expression and antioxidant enzymes were studied in the midgut of Bombyx mori larvae when reared on tropical mulberry plant varieties (Jorhat, TR10, BC2-59, and Hmute). In this study, the B. mori strain FC2 x FC1 showed a high expression of fibroin at both mRNA and protein levels when reared on four plant varieties. B. mori strains FC1 x FC2 (reared on Local, Jorhat and BC2-59) and CSR4 x CSR2 (reared on Jorhat, TR10 and BC2-59) had a higher level of expression of fibroin protein. The strain FC2 X FC1 showed relatively higher SOD and moderate catalase activities. This study reveals the differential expression of fibroin and tolerance to stress in B. mori strains which might justify the rationality of using the most suitable host plants and economically viable strains (FC2 X FC1) for producing commercially the best quality silk threads.

丝素蛋白长丝是由家蚕Bombyx mori生产的天然蛋白质，蚕茧中的丝线中的丝胶蛋白聚合物将其包围。在热带桑树品种（Jorhat，TR10，BC2-59和Hmute）上饲养的家蚕幼虫中肠中，研究了丝蛋白的基因表达和抗氧化酶。在这项研究中，家蚕双歧杆菌FC2 x FC1在四个植物品种上饲养时，在mRNA和蛋白质水平上都显示出高水平的丝素蛋白表达。桑蚕菌株FC1 x FC2（在Local，Jorhat和BC2-59上产生）和CSR4 x CSR2（在Jorhat，TR10和BC2-59上产生）具有较高的纤维蛋白蛋白表达水平。FC2 X FC1菌株显示相对较高的SOD和中等的过氧化氢酶活性。这项研究揭示丝心蛋白及公差的差异表达，来应力家蚕菌株可能证明使用最合适的宿主植物和经济上可行的菌株（FC2 X FC1）用于生产商业上最优质的丝线的合理性。