Studies On Biological Characters Of The Mutant In Colleterial Gland And Mapping Of The Mutant Gene (Ng) Using SSR Markers In Silkworm, Bombyx Mori

The character of no glue egg in silkworm follows the pseudo-maternal inherited mode and is mainly caused by mutation at the colleterial gland which secretes no or little glue-like substance and controlled by Ngene which was mapped at28.0of the silkworm classical genetic linkage group12. Currently, few reports about it were found, especially about the research of Nggene and its regulation mechanism.In this paper, morphologic changes of colleterial glands were observed and the main composition of secretion was determined in different developmental stages of No-Glue (Ng) mutant strain H9by using normal strain P50as a control. The results show that the colleterial gland is differentiated into two parts, a secretory region and a reservoir lobe. During the pupal-adult development of normal strain P50, the glands exhibited two distinct growth phases:a slightly increase until day8and abruptly increase toward adult emergence (10d); After oviposition, the storage lobe shrank markedly. However, for H9, all this changes were not distinctand. The secretory content of carbohydrates, free amino acids, lipids and proteins reaches the maximum at the day of adult emergence, respectively9.32μg/ml,0.086mg/ml,0.007mg/ml,8.7mg/ml for H9, while15.35μg/ml,0.117mg/ml,0.024mg/ml,15.3mg/ml for P50. In addition, the secretory proteins were analyzed by SDS-PAGE. Two differential proteins were identified as endothelial-monocyte activating polypeptide II from P50and myosin heavy chain variant from H9by mass spectrometry.In the silkworm, Bombyxmori, no glue egg is mainly controlled by Ng (No glue) gene located on the12th chromosome. Owning to a lack of crossing over in females, reciprocal backcrossed Fi (BCi) progenies were used for linkage analysis and mapping of the Ng gene based on the SSR linkage map using silkworm strains H9and P50, which are Ng mutant and normal to egg, respectively. The Ng gene was found to be linked to three SSR markers. Using a reciprocal BCiM cross, we constructed a linkage map of36.4cM, with Ng mapped at15.9cM and the nearest SSR marker at a distance of7.4cM. The result of kaikoblast shows that the physical distance between the near markers (containing Ng gene) is181.7Kb. Further analysis show that BGIBMGA005833, BGIBMGA005835and BGIBMGA005836are closer to Ng, and the BGIBMGA005835is nearest to Ng, which physical distance is only44Kb.In short, the above results in Bombyx mori have the important meaning to clarify the regulation mechanism of producing no glue egg and the fine positioning of Ng gene and to use this mutation characteristic for molecular assisted breeding.