基于分子系统发育和比较转录组学探讨中国洞穴小弱蛛属眼睛退化的遗传演化过程

洞穴动物的眼睛退化与视觉丢失的遗传演化过程长期以来是演化生物学研究的挑战。比较亲缘关系较近的真洞穴与地表动物的遗传演化过程可为性状丢失和平行演化提供新的思路和证据。中国洞穴小弱蛛属种类多，眼睛退化程度变化大，从轻微退化（6眼无色素等，分布于洞口或洞内）到严重退化（无眼等，仅分布于洞内），是研究洞穴眼睛退化机制的理想材料。本研究拟广泛收集中国洞穴小弱蛛，利用分子系统发育与比较转录组学手段探讨其眼睛退化的遗传演化过程。项目共分四部分：（1）经典分类与生物条形码；（2）构建分子系统发育树（16S rRNA等6基因片段），基于该亲缘关系、生境和眼睛退化程度等取样并进行转录组测序；（3）眼睛发生相关转录因子在地表与洞内的基因表达与演化分析；（4）视觉传导基因在地表与洞内的基因表达与演化分析。本研究结果不仅有助于了解洞穴蜘蛛眼睛退化的遗传基础，更为蜘蛛目眼睛发生、起源与演化提供新的，较高可信度的证据。

Understanding the genetic basis of eye reduction and vision loss in caves has challenged evolutionary biologists for many years. Comparing blind cave-dwelling organisms to their sighted close relatives provides an opportunity to dissect the evolutionary genomic processes involved in trait loss and parallel evolution. Leptonetela spiders, highly diverse, easily collected, mostly distributed in entrances of caves or nearby surface, or cave inside without light, exhibit varying degrees of eye reduction from slightly reduced, pigmented eyes (6 eyes, frequently distributed in entrances of caves or inside caves) to highly reduced, disorganized eye structures (6/4/2 eyes without pigment or eyes absent absolutely). Thereby, we can probe the molecular components of vision across a range of evolved eye reduction associated with a clear ecological factor (i.e., the absence of light in caves). We shall collect all known Leptonetela species in China, and carry out a systematic research on the evolutionary genomic processes underlying eye reduction in cave dwelling Leptonetela spiders using molecular phylogeny and Comparative transcriptomics methods. We plan to do our research from the following four aspects: (1) we shall present the classical morphological taxonomy and DNA barcoding on Chinese Leptonetela spiders; (2) we shall carry out a phylogenetic analysis based sequence data from six genes (16S rRNA, COI, H3, 28S rRNA, 18S rRNA, ITS2) using different parsimony methods and model-based approaches. We shall sample targeted individuals according to the above phylogenetic relationship, habitats (surface or entrance of cave, cave inside) and degrees of eye reduction (6 eyes or 4 eyes with pigment, 6/4/2 eyes without pigment or eyes absent absolutely), and then perform RNA-Seq transcriptom sequencing; (3) we shall analyze eye morphogenesis related gene expression and evolution in cave and surface Leptonetela spiders; (4) we shall analyze phototransduction gene expression and evolution in cave and surface Leptonetela spiders. The results from this study will not only enhance our understanding of genetic basis of eye reduction in cave dwelling spiders but also shed lights on the scientific issues of molecular evolution of spider version such as the issue of origin, evolution of spider eyes.