Developmental Biology 第四章果蝇胚胎早期 发育的分子基础
Developmental Biology 第四章 果蝇胚胎早期 发育的分子基础
Developmental Biology 、果蝇胚胎发育概况 Fig 5.1 Patterning of the Drosophila Dorsal embryo. The body plan is patterned along two distinct axes. The antero- posterior and dorso-ventral axes are at right angles to each other and are laid down in the egg. In the early embryo. the dorso-ventral axis is divided into four regions: mesoderm(red), ventral ectoderm (yellow), dorsal ectoderm (orange), and amnioserosa (an extra mbryo amnioserosa dorsal ectoderm tents embryonic membrane, green).The ventral ectoderm gives rise to both ventral epidermis and neural tissue. the dorsal ectoderm to epidermis, The Head antero-posterior axis becomes divided into different regions that later give rise prospective to the head, thorax, and abdomen. After postenor gut the initial division into broad body regions, tenor gut ventral ectoderm segmentation begins, The future segments endoderm mesoderm can be visualized as transverse stripes by staining for specific gene activity hese strpes demarcate 14 parasegment First instar larva 10 of which are marked. The embryo develops into a segmented larva. By the time the larva hatches, the 14 para. segments have been converted into telson thoracic (T1-T3)and abdominal (A1-A8) segments, which are offset from the T213A1A2A3M45A4)4 parasegments by one half segment. Different segments are distinguished by the patterns of bristles and denticles on the cuticle. Specialized structures, the Thoracic segments acron and telson, develop at the head and tail ends, respectively
Developmental Biology 一、果蝇胚胎发育概况
Developmental Biology 二、胚胎躯体轴线的建立由母体基因决定 Maternal ne Examples of regions of gene activity Fig 5.2 The sequential expression of different sets of genes estab ishes th body plan along the antero-posterio axis. After fertilization bicoid (bcd) g母体基因产物量或 coid mRNA, are translated. They provide positional information whi activates the zygotic gones. The four 活性形成空间分布 bp3上的差异,在A Zygotic genes gap genes, the pair-rule genes, the segment polarity genes, and the selector. or homeotic, genes. The gap P和D-V轴线的不 hunchback ihoj 1同区域激活不同的 genes define regional differences that nd foreshadow 基因,使不同区域 Pair-rule egment polarity genes elaborate the ttern in the segments, and segment 的基因活性谱不同 is determined by the selector maem而出现分化。 Selector abdominal/A (abd-A)
Developmental Biology 二、胚胎躯体轴线的建立由母体基因决定 母体基因产物量或 活性形成空间分布 上的差异，在A－ P和D－V轴线的不 同区域激活不同的 基因，使不同区域 的基因活性谱不同 而出现分化
Developmental Biology 1.A-P轴线由三类母体基因控制:突变鉴定 anterior class, posterior class, terminal class. wild-type egg fate ma wild-type larva Fig 5.3 The effects of mutations in the maternal gene system. Mutations in maternal genes lead to deletions and abnormalities in anterior, posterior, or terminal structures, The wild-type fate give rise to particular regions ang map shows which regions of the lc son head abdomen structures in the larva. Regions that are thorax affected in mutant eggs and which lead to lost or altered structures in the larva Mutant eggs Mutant embryos Regions affected are shaded in red. In bicoid mutants there is a partial loss of antenor structures bicod mutant and the appearance of a postenor structure-the telson-at the anterior end, nanos mutants lack a large part of the posterior region. torso mutants lack both acron and telson nanos mutant
Developmental Biology 1. A－P轴线由三类母体基因控制：突变鉴定 anterior class, posterior class, terminal class
Table 9.1 Maternal effect genes that effect the anterior-posterior polarity of the Drosophila embryo Gene Mutant phenotype Proposed function and structure ANTERIOR GROUP bicoid (bcd) Head and thorax deleted, replaced by Graded anterior morphogen; inverted telson contains homeodomain: represses caudal exuperantia(exu) Anterior head structures deleted Anchors bicoid mRNA swallow(swa) Anterior head structures deleted Anchors bicoid mRNP POSTERIOR GROUP nanos(nos) o abdomen Posterior morphogen represses hunchback tudor(tud) No abdomen, no pole cells Localization of Nanos oskar(osk) No abdomen, no pole cells Localization of Nanos sa(vas) No abdomen, no pole cells; oogenesis defective Localization of Nanos valois(val) No abdomen, no pole cells; cellularization Stabilization of the Nanos localization defective complex pumilio(pum) No abdomen Helps Nanos protein bind hunchback message caudal (cad) No abdomen Activates posterior terminal genes TERMINAL GROUP torso(to No termini Possible morphogen for termini trunk(trk) No termini Transmits Torsolike signal to torso fs(I)NasrarUSs(I)N] No termini: collapsed eggs Transmits Torsolike signal to Torso fs( 1)poleholel s(1)ph) No termini; collapsed eggs Transmits Torsolike signal to torso After Anderson 1989
Developmental Biology