蚂蚁生殖分化的神经激素调控机制研究

The origin of animal society is a transitional landmark in evolution. Eusocial insects such as ants are organized in colonies composed of different castes with differentiation of reproduction and division of labor. Queen dominates in reproduction while worker involves in brood-caring, foraging and defense. When a virgin gyne (unmated queen) accomplishes mating and develops into a mature queen, its physiology, behavior and reproductive ability have dramatic changes. Previously, we have adopted comparative transcriptomics methods to trace brain gene expression dynamics during queen development and identified several key candidate neuropeptide genes that are differentially expressed during gyne/queen transition which have crosstalk with insulin signaling pathway, including neuroparsin, tachykinin and drosulfakinin. We will focus on dissecting the molecular functions of these key candidate neuropeptide genes. Firstly, we will characterize their spatial expression patterns. Then, by performing RNA interference, gene editing or injecting neuropeptide into ants' hemolymph to inhibit or promote gene functions, the physiological, behavioral and reproductive traits of queens will be assayed. From above experiments, we will reveal neural hormone regulatory mechanisms underlying queen development and the core gene regulatory network responsible for the development of reproductive division of labor in eusocial insects.

动物社会组织的出现是生命演化历程中的重大转折性事件。在蚂蚁为代表的社会性昆虫中出现了生殖分化及劳动分工。蚁后负责生殖，而工蚁则失去生殖潜能，专门负责育幼、觅食、防御等工作。在个体发育层面，雌性处女生殖蚁完成交配转变为成熟蚁后过程中其生理、行为及生殖力均会发生剧烈变化。通过比较转录组研究方法，追踪蚁后建立过程中大脑基因表达动态变化，我们鉴定出若干差异表达的，与insulin信号通路互作的神经肽基因，包括：neuroparsin、tachykinin及drosulfakinin等。本项目将着重围绕这3个神经肽开展分子功能实验，检测神经肽基因的大脑空间表达模式；采用基因沉默、基因编辑及直接注射多肽的方法，抑制或促进基因功能，检测蚁后生理、行为、生殖力所受到的影响。通过上述实验解析蚁后建立过程中的神经激素调控机制，从个体发育角度挖掘社会性昆虫生殖分化的核心基因调控网络。

蚂蚁处女生殖蚁（gyne）必须通过交配，成功受精之后才能转变为成熟蚁后（queen）。在此转变过程中，伴随着生理和行为的剧烈变化：蚁后的活动力降低，卵子发生极度活跃，几乎终身待在巢内专职产卵，寿命也会显著延长；而长期不能交配的gyne，其卵子发生会被抑制，而且其行为会偏向工蚁，会表现出更多的育幼及觅食倾向。Gyne到queen的转变过程中伴随着明显的大脑可塑性变化及基因调控网络的重塑，其中包括若干差异表达的神经肽基因。Queen与相同年龄的gyne相比，neuroparsin的表达水平受到抑制，随着年龄增大，抑制更加明显。我们发现neuroparsin表达在中央神经分泌细胞，neuroparsin多肽合成后会分泌到血淋巴，随体液循环作用到全身效应组织。在gyne中注射dsRNA敲降neuroparsin会促进其卵子发生，使其行为模式偏向queen；相反，在queen中注射neuroparsin多肽会抑制其生殖，使其行为模式偏向于gyne。我们检测了敲降neuroparsin或提高neurparsin水平后在大脑和卵巢中所引起的基因表达水平的变化，发现在卵巢黄体中表达的一个JHBP（Juvenile Hormone Binding Protein）基因被neuroparsin正调控，敲降JHBP后，会促进gyne的卵子发生；而Shadow基因（编码合成Ecdysone的细胞色素P450蛋白）则被neuroparsin负调控。这提示大脑分泌的神经肽neuroparsin通过调控卵巢内激素合成或响应而影响了蚁后的生殖及行为，我们进一步发现neuroparsin对生殖及行为的调控功能在多种蚂蚁进化支系中都是保守的。