MAPK信号通路参与热激诱导家蚕未受精卵发生孤雌生殖发育的研究

An Investigation on MAPK Signal Pathway Involved in Thermal Induction Parthenogenesis of Non-fertilized Silkworm Eggs

通过检测家蚕未受精卵细胞中参与丝裂原活化蛋白激酶(MAPK)信号通路的几个关键基因的转录水平,分析热激诱导家蚕未受精卵发生孤雌生殖发育的分子机制。首先基于家蚕未受精卵RNA-seq数据分析表明,在家蚕孤雌生殖系和有性生殖系间,无论是经过热激诱导处理(46℃水浴18 min)或未热激处理的未受精卵,MAPK途径都存在差异表达的基因。实时荧光定量PCR(qRT-PCR)检测分析MAPK途径的mos、mek、erk和p38mapk基因在热激诱导前家蚕孤雌生殖系及有性生殖系未受精卵之间的转录水平差异:位于MAPK通路中上游的2个基因mos和mek,无论中系品系还是日系品系中,均表现为在孤雌生殖系表达极显著下调(P<0.01);而位于MAPK通路下游的基因erk和p38mapk,其转录水平在中系品系的孤雌生殖系与有性生殖系间无显著性差异,但在日系品系中则表现为在孤雌生殖系中极显著下调(P<0.01)。qRT-PCR检测分析家蚕孤雌生殖系未受精卵的4个基因在热激诱导孤雌生殖发育过程中的转录水平变化也表现出差异性:热激处理后mos和mek的转录水平极显著下调(P<0.01),并维持在低水平;p38mapk则在热激处理前后保持稳定;而热激处理后erk基因的转录先显著升高(P<0.05),而后逐步下降,并维持在热激处理前的水平。研究结果提示,MAPK途径可能参与了热激诱导家蚕孤雌生殖发育过程。

To explore the molecular mechanism of parthenogenesis in non-fertilized eggs of silkworm（ Bombyx mori）,the transcriptional level of several key genes in the mitogen-activated protein kinase（ MAPK） cascade of non-fertilized silkworm eggs was determined. Based on RNA-seq data of non-fertilized silkworm eggs,differentially expressed genes in MAPK pathway were identified between parthenogenetic line and amphigenetic line and between non-fertilized eggs after heat shock treatment at 46 ℃ for 18 min and non-fertilized eggs without heat shock treatment. qRT-PCR was conducted to compared the transcriptional levels of mos,mek,erk and p38 mapk genes in MAPK pathway of non-fertilized eggs between parthenogenetic line（ PL） and its original amphigenetic line（ AL）. The expressional levels of mos and mek,which are the up- and middle-stream genes in MAPK pathway,were significantly down-regulated in silkworm varieties of Chinese and Japanese strains（ P 0. 01）. The expressional levels of down-stream genes erk and p38 mapk in MAPK pathway had no significant difference between AL and PL of Chinese strain silkworm varieties,but those in PL of Japanese strain silkworm varieties were significantly down-regulated（ P 0. 01）. qRT-PCR assay revealed that the expressional profiles of those four genes showed difference in non-fertilized eggs of PL during parthenogenesis after heat shock. The expressional levels of mos and mek were significantly down-regulated（ P 0. 01） and maintained at low level after heat shock,while the expressional level of p38 mapk kept constant before and after heat shock. On the contrary,the expression level of erk was increased first after heat shock（ P 0. 05）,and then gradually declined to normal level before heat shock. These results showed that the MAPK pathway is probably involved in the thermal induction of parthenogenesis in silkworm.