Duplicated alkaline phosphatase genes in Bombyx mori ; structure and expression regulation

为了了解家蚕碱性磷酸酶（ALP）基因的结构，分别分离了mALP和sALP的基因组克隆。然而，这两个基因都位于一个小的基因组区域（11,495bp），可能在III染色体上。它们之间存在一个间隔序列（4341bp）。转录方向相同，mALP基因位于sALP基因的上游。mALP基因有5个外显子，而sALP基因有4个。这种差异与sALP基因中没有与mALP对应的内含子有关。每个外显子的核苷酸序列高度相同（60-80%）。另一方面，它们的内含子没有明显的同源性，尽管它们的相对位置很一致。RNA印迹分析表明，在孵化前首先出现了来自mALP基因的2.2Kb mRNA和来自sALP基因的2.0Kb和2.4Kb两个转录本。3种转录本的数量在5龄幼虫期第6天达到最大值，在变质期迅速消失。因此，它们的转录在时间上对幼虫中肠上皮的存在具有特异性，因此家蚕的摄食活性，尽管它们的转录的外观特征和消失阶段并不完全相同：在胚胎发生时，sALP转录的增加速度慢于mALP，并且在结束时比mALP早几天消失。

In order to know the structure of alkaline phosphatase (ALP) genes in the silkmoth, Bombyx mori, genomic clones each for mALP and sALP were independently isolated. Both genes, however, were located to a small genomic region (11,495bp) presumably on III chromosome. There were an intervening sequence (4,341bp) between them. The direction of transcription were the same : the mALP gene was located to upstream of the sALP gene. The mALP gene has five exons, but the sALP gene has four. This difference is involved in no intron corresponding to the mALP second one in the sALP gene. The nucleotide sequence of each exon were highly identical (60-80%) between them. On the other hands, there was no significant homology in their introns, although their relative positions accorded well.RNA blot analysis demonstrated that a 2.2Kb mRNA from the mALP gene and two transcripts, 2.0Kb and 2.4Kb, from the sALP gene appeared first just before hatching. The amounts of all three transcripts reached their maxima at the 6th day of the fifth instar larval stage and they disappeared rapidly in the metamorphic stage. Accordingly, their transcriptions are temporally specific for the existence of the larval midgut epithelium, thus the feeding activity of B.mori, although the appearance profiles and the disappearing stages of their transcription were not completely the same : sALP transcripts increased slower than that of mALP in embryogenesis and disappeared a few days earlier than that of mALP at the end.