Glutathione S-transferases (GSTs) are a multifunctional supergene family and some play an important role in insecticide resistance. We have identified 23 putative cytosolic GSTs by searching the new assembly of the Bombyx mori genome sequence. Phylogenetic analyses on the amino acid sequences reveal that 21 of the B. mori GSTs fall into six classes represented in other insects, the other two being unclassified. The majority of the silkworm GSTs belong to the Delta, Epsilon, and Omega classes. Most members of each class are tandemly arranged in the genome, except for the Epsilon GSTs. Expressed sequence tags (ESTs) corresponding to 19 of the 23 GSTs were found in available databases. Furthermore RT-PCR experiments detected expression of all the GSTs in multiple tissues on day 3 of fifth instar larvae. Surprisingly, we found little or no expression of most Delta and Epsilon GSTs in the fat body, which is thought to be the main detoxification organ. This may explain the sensitivity of the silkworm to certain insecticides. Our data provide some insights into the evolution of the B. mori GST family and the functions of individual GST enzymes.

中文翻译：

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家蚕谷胱甘肽S-转移酶的鉴定，基因组组织和表达模式。

谷胱甘肽S-转移酶（GST）是一个多功能的超基因家族，其中一些在杀虫剂抗性中起重要作用。通过搜索家蚕基因组序列的新装配，我们已经鉴定出23种推测的胞质GST。氨基酸序列的系统发育分析表明，桑蚕中的21种GST属于其他昆虫所代表的六类，另外两类未分类。大多数蚕GST属于Delta，Epsilon和Omega类。除Epsilon GST外，每个类别的大多数成员都串联排列在基因组中。在可用数据库中找到了与23种GST中的19种相对应的表达序列标签（EST）。此外，RT-PCR实验在第五龄幼虫的第3天检测到了多种组织中所有GST的表达。出奇，我们发现在脂肪体内，大多数Delta和Epsilon GST几乎没有表达，甚至没有表达，这被认为是主要的排毒器官。这可以解释家蚕对某些杀虫剂的敏感性。我们的数据为桑蚕GST家族的进化和个别GST酶的功能提供了一些见识。