家蚕裸蛹基因(Nd)的SSR定位

家蚕裸蛹是自然突变产生的,裸蛹基因(Nd)与丝素重链基因(Fib-H)同处于第25染色体上,二者紧密连锁。利用家蚕雌性不交换的特点,以家蚕正常茧品种P50和裸蛹品种Nd为亲本获得P50×(P50×Nd)和(P50×Nd)×P50回交群体(分别记为BC1M和BC1F),再用已经构建的家蚕SSR分子标记连锁图谱对Nd基因进行定位,共筛选出7个与Nd基因连锁的SSR标记。BC1F群体中的所有裸蛹个体均表现出与(P50×Nd)F1相同的杂合型带型;而所有正常茧个体带型与亲本P50一致,为纯合型。利用另一个群体BC1M构建了Nd基因的遗传连锁图,连锁图的遗传距离为96.8 cM,Nd基因位于60.8 cM。同时得到了2个与Nd紧密连锁的SSR标记S2511及S2513,与Nd基因的距离分别为0.1 cM和1.1 cM。

Mapping of the Naked Pupa(Nd) Gene in Silkworm Bombyx mori Using SSR Markers

Naked pupa of the silkworm Bombyx mori is originated from a natural mutation. The naked (Nd) gene and the fibroin heavy-chain gene (Fib-H) had been found to locate on the 25th chromosome and are closely linked. Owing to the lack of crossing over in silkworm females, P50, a silkworm strain that spins normal cocoons, and Nd, a strain with naked pupa, were used as parents to obtain backcross populations P50×(P50×Nd) and (P50×Nd)×P50, designated as BC_1M and BC_1F respectively. Subsequently, mapping of Nd gene was conducted using the constructed simple sequence repeat (SSR) molecular marker linkage maps, and 7 SSR markers were found to link with Nd gene. It was found that all naked pupae from BC_1F progeny had the same heterozygous bands with the (P50×Nd) F_1 hybrid, and all pupae from normal cocoons had the same homozygous bands with the parental strain P50. By utilizing another BC_1M population, we constructed a genetic linkage map for the Nd gene. The genetic distance of this map is of 96.8 cM with the Nd gene located at 60.8 cM. Meanwhile, 2 closely linked SSR markers, namely S2511 and S2513 which is 0.1 cM and 1.1 cM away from the Nd gene respectively, were obtained.