家蚕热休克蛋白70家族基因的染色体定位及表达特征

Chromosomal Localization and Expressional Profile of Heat Shock Protein 70 Family Genes in Silkworm,Bombyx mori

热休克蛋白70家族(Hsp70)是非常保守的蛋白家族,每个物种的Hsp70家族都有多个成员,每个成员都可能具有特殊的功能。为了能够对家蚕Hsp70家族各成员进行科学命名和了解其特有的功能,分析家蚕Hsp70家族成员的编码基因及其在染色体上的定位,并通过实时荧光定量PCR方法检测这些基因在5龄第3天幼虫中肠、脂肪体和丝腺组织中的转录表达情况。家蚕诱导型Hsp70家族成员Bmhsp70A和Bmhsp70B的编码基因集中分布在第27号染色体上,有多个拷贝;组成型Bmhsp70家族成员的编码基因则分布在不同的染色体上,一般仅有1个拷贝。家蚕Hsp70家族基因中有10个能转录并翻译蛋白质产物的成员,还有1个能正常转录但不能正确翻译的假基因。实时荧光定量PCR结果表明:在常温(25℃)条件下,组成型Bmhsp70家族基因Bmhsc70-4和Bmhsc70-3的表达水平较高,而其它基因成员的表达水平则相对较低,诱导型Bmhsp70家族基因成员在常温下也有一定程度的基础表达;40℃热激2 h后,Bmhsp70家族所有基因的表达水平都有所升高,其中诱导型Bmhsp70家族基因Bmhsp70B和Bmhsp68的转录表达上升水平远高于组成型Bmhsp70家族基因Bmhsc70-3和Bmhsc70-4。不同表达类型的家蚕Hsp70家族基因成员在5龄幼虫中肠、丝腺和脂肪体中的表达情况不同,热激2 h后的表达变化规律也不完全相同,提示家蚕Hsp70家族成员具有各自特殊的功能。

Heat shock protein 70 （Hsp70） family is very conservative. Hsp70 family has multiple members in each spe cies and the functional features of each family member can be quite different. In order to name each Hsp70 family mem ber of silkworm （ Bombyx mori） in accordance with the established nomenclature and understand unique functions of each member, the present study analyzed genes encoding silkworm Hsp70 family members and their locations on chro mosomes and employed realtime fluorescent quantitative PCR to determine their transcriptional levels in midgut, fat body and silk gland of day 3 silkworm larvae of the 5th instar. It was found that genes encoding the inducible silkworm Hsp70 family members Bmhsp70A and Bmhsp70B are collectively located on chromosome 27 with multiple copies, while thoseencoding the constitutive Bmhsp70 family members are scattered on different chromosomes with only one copy in general. Ten of the silkworm Hsp70 family genes can be transcribed and translated into proteins, and one of them can be transcribed but can not be translated correctly and is thus regarded as a pseudogene. Realtime fluores cent quantitative PCR analysis revealed that, at room temperature （25 °C）, transcriptional levels of the constitutive Bmhsp70 family genes BmhscTO4 and Bmhsc703 were high, while those of the other family members were rela tively low. The inducible Bmhsp70 family members had basal expression at room temperature as well. After heat shock at 40 °C for 2 h, the transcriptional levels of all BmhspT0 member genes were increased, among which the expressional lev els of inducible Bmhsp70 family genes Bmhsp70B and Bmhsp68 were far higher than those of constitutive Bmhsp70 fami ly genes Bmhsc703 and Bmhsc704. Silkworm Hsp70 family genes of different expressional patterns had different tran scriptional levels in midgut, fat body and silk gland of the 5th instar silkworm larvae. The expressional variation of them was also different upon heat shock for 2 h, suggesting that different members of silkworm Hsp70 have their own distinct functional features.