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，这两个基因被定位到一个小的基因组区域（11，495 bp）推测在III染色体上。它们之间存在一个4, 341 bp的插入序列。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个外显子。这种差异与sALP基因中没有对应于mALP第二内含子的内含子有关。它们之间每个外显子的核苷酸序列高度一致（60-80%）。RNA印迹分析表明，在孵化前最先出现的是mALP基因的2.2Kb mRNA和sALP基因的2.0Kb和2.4Kb转录本。三种转录本的含量均在五龄幼虫期的第6天达到最大值，在变态期迅速消失。因此，它们的转录具有时间特异性，即中肠上皮细胞的存在和家蚕的摄食活动具有时间特异性，尽管它们的转录的出现和消失阶段并不完全相同：在胚胎发育过程中，sALP转录的增加速度比mALP慢，在胚胎发育结束时，sALP转录的消失时间比mALP早几天。

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.