滞育诱导发生温度与光周期对家蚕垂体同源框激素基因Pitx表达的影响

家蚕垂体同源框激素PITX对滞育激素DH的分泌与作用有直接影响。为了探讨家蚕滞育的信号传导机制,研究了3种典型的滞育发生诱导温度和光周期条件对Pitx基因表达的影响。结果显示,亲代催青期滞育卵诱导发生条件25LL显著上调了蚕卵中Pitx基因表达水平。整个世代持续25LL环境中,3龄前幼虫和成虫体内,Pitx基因的表达水平高于15DD环境中的蚕体;胚后蚕体Pitx基因的表达水平有显著组织差异,幼虫眠中表达水平有下调趋势。子代卵内Pitx基因mRNA的水平变化与亲代诱导所致的蚕卵滞育性差异密切相关,滞育性卵中未检测到母源Pitx基因的mRNA,卵龄12～24h的胚胎发生期则有较高水平的表达,卵龄72h后的滞育发生阶段后只有痕迹量;非滞育性卵中有较高水平的母源Pitx基因mRNA,胚胎发生及发育期,Pitx基因转录水平显著高于滞育性卵;亲代20LD催青条件下所产卵滞育性不稳定,Pitx基因的mRNA水平显著高于滞育性卵,也高于非滞育性卵。亲代卵的孵化温度与光周期决定子代卵的滞育性,也影响到Pitx基因表达水平,子代卵内Pitx基因表达水平高低不是蚕卵滞育与否的关键。

Effects of Diapause-induction Temperature and Photoperiod on Expression of Silkworm Pituitary Homeobox Gene pitx

Pituitary homeobox hormone （PITX） affected directly on the secretion and the role of DH in Bombyx mori. In order to explore the signal transduction pathway of diapause, we investigated the effects of three typical diapause inducing temperature and photo- period on expression of Pitx gene. The results showed that the constant illumination at 25~C （25LL） significantly up-regulated the ex- pression level. The Pitx mRNA level from 1st to 3rd instar larvae and adults in 25LL were higher than the which in 15DD. Moreover, the gene expression level were significantly differences between tissues, and down-regnlated during moulting period. The Pitx gene mR- NA levels in progeny eggs were influenced by diapause-inducing temperature and photoperiod during the parental stage. The maternal Pitx gene mRNA had not detected from diapause eggs. Howerer, the gene up-regnlated the expression level during egg age of 12h to 24h, and almost stoped the expression in diapause occuring stage elder than age 72h. The non-diapause eggs had higher level of mater- nal Pitx mRNA, and had higher gene expression level during embryogenesis and development period. The diapause of eggs from 20LD parental conditions were unstable. However, the Pitx gene mRNA level in those eggs were significantly higher than the level in dia- pause eggs and non-diapause eggs. The incubation temperature and photoperiod of parental eggs determined the diapause of progeny eggs, and also affected the Pitx gene expression level. Anyway, the gene expression level of progeny eggs might be not related to the diapause of eggs itself.