Nematogalectin, a nematocyst protein with GlyXY and galectin domains, demonstrates nematocyte-specific alternative splicing in Hydra
Nematogalectin, a nematocyst protein with GlyXY and galectin domains, demonstrates nematocyte-specific alternative splicing in Hydra
复制标题
DOI：
10.1073/pnas.1003256107
复制
发表时间：
2010-10-26
影响因子：
11.1
通讯作者：
Gojobori, Takashi
中科院分区：
文献类型：
--
作者：
Hwang, Jung Shan;Takaku, Yasuharu;Gojobori, Takashi
分类学限制基因或谱系特异性基因有助于后生动物的形态多样性，并为特定分类群提供适应特定环境的独特功能。为了了解这些基因是如何产生并参与形态进化的，我们研究了水螅中一种名为半乳糖凝集素的基因，它在刺胞的形成中起着结构性作用，刺胞是刺胞门所特有的。半乳糖凝集素是一种28 kDa的蛋白质，具有N-末端GlyXY结构域（甘氨酸，随后是两个疏水氨基酸），其可以形成胶原三螺旋，随后是半乳糖结合凝集素结构域。半乳糖凝集素转录物的选择性剪接允许该基因编码两种蛋白质，半乳糖凝集素A和半乳糖凝集素B。我们证明，在不同的包囊类型中，半乳糖凝集素A和B的表达是相互排斥的：Desmonemes表达半乳糖凝集素B，而stenoteles和isorhizas在分化早期表达半乳糖凝集素B，然后是半乳糖凝集素A。与水螅一样，海洋水螅动物Clytia也有两种半乳糖凝集素转录本，它们在不同的细胞类型中表达。相比之下，珊瑚虫只有一个半乳糖凝集素基因。基因同源性表明，在珊瑚虫和水母虫分化之前，半乳糖凝集素B外显子的串联重复产生了半乳糖凝集素A，并且半乳糖凝集素A随后在珊瑚虫中丢失。半乳糖凝集素A的出现可能在水母谱系中的微囊的形态多样化中发挥了作用。
Taxonomically restricted genes or lineage-specific genes contribute to morphological diversification in metazoans and provide unique functions for particular taxa in adapting to specific environments. To understand how such genes arise and participate in morphological evolution, we have investigated a gene called nematogalectin in Hydra, which has a structural role in the formation of nematocysts, stinging organelles that are unique to the phylum Cnidaria. Nematogalectin is a 28-kDa protein with an N-terminal GlyXY domain (glycine followed by two hydrophobic amino acids), which can form a collagen triple helix, followed by a galactose-binding lectin domain. Alternative splicing of the nematogalectin transcript allows the gene to encode two proteins, nematogalectin A and nematogalectin B. We demonstrate that expression of nematogalectin A and B is mutually exclusive in different nematocyst types: Desmonemes express nematogalectin B, whereas stenoteles and isorhizas express nematogalectin B early in differentiation, followed by nematogalectin A. Like Hydra, the marine hydrozoan Clytia also has two nematogalectin transcripts, which are expressed in different nematocyte types. By comparison, anthozoans have only one nematogalectin gene. Gene phylogeny indicates that tandem duplication of nematogalectin B exons gave rise to nematogalectin A before the divergence of Anthozoa and Medusozoa and that nematogalectin A was subsequently lost in Anthozoa. The emergence of nematogalectin A may have played a role in the morphological diversification of nematocysts in the medusozoan lineage.