Sommer R J, Tautz D
Zoologisches Institut der Universität München, Germany.
Dev Genet. 1994;15(1):32-7. doi: 10.1002/dvg.1020150105.
The mesodermal region in Drosophila is determined by a maternally derived morphogenetic gradient system which specifies the different cell fates along the dorsoventral axis, including the prospective mesodermal cells at the ventral side of the embryo. There are at least two zygotic target genes, twist and snail, which are required for mesoderm formation in Drosophila. To analyze whether a similar mode of mesoderm specification might also apply to short germband insect embryos, we have cloned twist and snail-related gene fragments from the flour beetle Tribolium and have analyzed their expression pattern. Both genes are expressed in a ventral stripe at early blastoderm stage, which is restricted to the region of the developing germ rudiment. The cells expressing the two genes are those that invaginate during gastrulation, indicating that the early stages of mesoderm specification are indeed very similar between the two species. Interestingly, both genes are also expressed during germband extension in a subregion of the growth zone of the embryo which forms the mesodermal cells. This suggests that the expression of the two genes is required for mesoderm formation both at early blastoderm stage and during germband elongation until the end of the segmental growth process.
果蝇中的中胚层区域由一种母体来源的形态发生梯度系统决定，该系统沿背腹轴指定不同的细胞命运，包括胚胎腹侧的预期中胚层细胞。果蝇中胚层形成至少需要两个合子靶基因，即twist和snail。为了分析类似的中胚层特化模式是否也适用于短胚带昆虫胚胎，我们从黄粉虫赤拟谷盗中克隆了与twist和snail相关的基因片段，并分析了它们的表达模式。这两个基因在胚盘早期阶段均在腹侧条带中表达，该条带局限于发育中的胚基区域。表达这两个基因的细胞是在原肠胚形成期间内陷的细胞，这表明这两个物种中胚层特化的早期阶段确实非常相似。有趣的是，在胚带延伸期间，这两个基因也在胚胎生长区的一个子区域中表达，该子区域形成中胚层细胞。这表明这两个基因的表达在胚盘早期阶段以及胚带伸长直至节段生长过程结束期间的中胚层形成中都是必需的。
