Divergent RNA Localisation Patterns of Maternal Genes Regulating Embryonic Patterning in the Butterfly Pararge aegeria
Divergent RNA Localisation Patterns of Maternal Genes Regulating Embryonic Patterning in the Butterfly Pararge aegeria
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DOI：
10.1371/journal.pone.0144471
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发表时间：
2015-12-03
期刊：
影响因子：
3.7
通讯作者：
Breuker, Casper J.
中科院分区：
文献类型：
--
作者：
Carter, Jean-Michel;Gibbs, Melanie;Breuker, Casper J.
在昆虫中，负责胚胎沿前后轴形成图案的母性效应基因广泛保守。这些母性效应基因的精确功能是其mRNA在卵母细胞中定位的结果。黑腹果蝇的主要发育机制已经被阐明，但最近的研究表明，其他昆虫目的RNA定位模式经常出现分歧。最近的一项研究表明，在羽衣蝶中，囊胚胚（即胚带）和胚外组织（即浆膜）之间的区别早在囊胚细胞化之前就已经在卵巢的卵母细胞中确定了。为了研究雌性蝴蝶在生殖带区域内指定AP轴的程度和模式，以及她是否指定了一种种质，我们对埃氏斑蝶卵巢和早期胚胎的卵母细胞进行了原位杂交实验。研究了以下关键母性效应基因的RNA定位：尾侧（cad）、正畸（otd）、驼背（hb）和四个纳米（nos）类似物，以及包含与oskar共享的关键功能域（OST-HTH/LOTUS）的TDRD7基因。TDRD7主要局限于卵泡细胞，而hb则完全合子转录。一些nos类似物，otd和cad的RNA在皮层区域显示出复杂的定位模式，预示着胚芽带（即胚芽皮层）。有趣的是，otd位于胚皮层前部内外。nos-O转录本在胚皮层中间形成一个明显的颗粒状环，可能预示着种系干细胞形成的区域。这些蝴蝶RNA定位模式与其他昆虫高度不同，突出了不同昆虫目母体调节后代早期胚胎发生的不同方式。
The maternal effect genes responsible for patterning the embryo along the antero-posterior (AP) axis are broadly conserved in insects. The precise function of these maternal effect genes is the result of the localisation of their mRNA in the oocyte. The main developmental mechanisms involved have been elucidated in Drosophila melanogaster, but recent studies have shown that other insect orders often diverge in RNA localisation patterns. A recent study has shown that in the butterfly Pararge aegeria the distinction between blastodermal embryonic (i.e. germ band) and extra-embryonic tissue (i.e. serosa) is already specified in the oocyte during oogenesis in the ovariole, long before blastoderm cellularisation. To examine the extent by which a female butterfly specifies and patterns the AP axis within the region fated to be the germ band, and whether she specifies a germ plasm, we performed in situ hybridisation experiments on oocytes in P. aegeria ovarioles and on early embryos. RNA localisation of the following key maternal effect genes were investigated: caudal (cad), orthodenticle (otd), hunchback (hb) and four nanos (nos) paralogs, as well as TDRD7 a gene containing a key functional domain (OST-HTH/LOTUS) shared with oskar. TDRD7 was mainly confined to the follicle cells, whilst hb was exclusively zygotically transcribed. RNA of some of the nos paralogs, otd and cad revealed complex localisation patterns within the cortical region prefiguring the germ band (i.e. germ cortex). Rather interestingly, otd was localised within and outside the anterior of the germ cortex. Transcripts of nos-O formed a distinct granular ring in the middle of the germ cortex possibly prefiguring the region where germline stem cells form. These butterfly RNA localisation patterns are highly divergent with respect to other insects, highlighting the diverse ways in which different insect orders maternally regulate early embryogenesis of their offspring.