The Developmental Biology of Hybrid Incompatibility

对该项目的非技术描述：在进化过程中，物种经常被分成不同的亚群，不同亚群的成员可能变得无法彼此产生健康的后代。相反，后代可能生病或不育，甚至在成年前死亡。在这一点上，科学家认为这些亚群是不同的物种。当它们死亡时，它们的死亡是由于发育过程中的错误造成的，这个项目的目标是确定是否有一般规则来解释为什么这些杂交后代在何时以及如何死亡。也许这些错误是特殊的，每个人都以自己的方式死亡。也许两个物种之间的杂交以一种方式死亡，但另外两个物种之间的杂交以不同的方式死亡。或者，在一组相关物种中，杂交种死亡时间和方式的相同模式被反复重复，因为发育的某些部分和阶段比其他部分和阶段对干扰更敏感。为了验证哪一种是正确的，这个项目将使用一组相关的蛔虫，它们看起来非常相似，但它们的杂交后代往往会作为胚胎死亡。这项对物种不亲和性的调查也将构成两个实践科学模块的基础，这些模块与加州中学生物学标准保持一致。在一个项目中，学生们将自己测试不同的物种是否可以交配，在另一个项目中，他们将在野外诱捕蛔虫，并使用它们的DNA来识别物种或发现它们是科学上的新物种。该项目的技术描述：随着物种在进化过程中分离，基因组水平上的不相容可能会累积并推动这一过程。这些不亲和性通常在发育过程中表现出来，使杂交后代无法存活或不育。这一过程的发育生物学研究相对较少。显微镜技术的最新进展使实时、全面、定量地测量越来越多的生物体发育的关键方面成为可能。这种能力使我们有可能测试关于构成有机体的细胞过程的可变性的假设，比较物种内部和物种之间的这些假设，并准确地剖析当发育出错时，什么会被破坏。通过系统杂交、发育中胚胎的高分辨率4D显微镜和有针对性的基因表达测量，该项目将以线虫蛔虫属为模型系统，测试关于杂交不育的发育生物学的三个主要假说。这些线虫是这类研究的理想选择，因为它们的正常发育是刻板的和可重复的，不同物种即使胚胎死亡也经常会彼此交配，而且该属至少包括两个处于物种形成过程中的物种对，并保持部分干扰。这项研究将确定杂交胚胎死亡的时间和方式，发育中第一批缺陷出现的地点和时间，这些缺陷是由异常细胞运动还是由异常细胞命运决定引起的，以及这些模式是否在整个属内是系统性的，或者对于每个胚胎或物种对来说是独特的。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical description of the project: Over the course of evolution, species often become divided into subgroups, and members of different subgroups may become unable to produce healthy offspring with each other. Instead, the offspring can be sick or sterile or even die before reaching adulthood. At that point, scientists consider these subgroups to be different species. When they die, their deaths result from mistakes made during development, and the goal of this project is to determine whether there are general rules that explain why these hybrid offspring die when and how they do. Perhaps these mistakes are idiosyncratic, with each individual dying in its own way. Perhaps hybrids between two species die in one way but hybrids between two others die in a different way. Or perhaps, within a group of related species, the same pattern of when and how hybrids die is repeated over and over because some parts and phases of development are more sensitive to disruption than others. To test which of these is the case, this project will use a group of related roundworms which look very similar but whose hybrid offspring tend to die as embryos. This investigation of species incompatibility will also form the basis for two hands-on science modules aligned with the California secondary school biology standards. In one students will test for themselves whether different species can mate, and in the other they will trap roundworms in the wild and use their DNA to identify the species or to discover that they are new to science.Technical description of the project: As species separate during evolution, incompatibilities at the genome level can accumulate and ratchet the process forward. These incompatibilities often play out during development and render hybrid offspring inviable or infertile. The developmental biology of this process is relatively little studied. Recent advances in microscopy have made it possible to quantitatively and comprehensively measure key aspects of development in real time in an increasing range of organisms. This capacity makes it possible to test hypotheses about the variability of the cellular processes that construct organisms, to compare these both within and between species, and to dissect exactly what is disrupted when development goes wrong. Through a combination of systematic crosses, high-resolution 4D microscopy of developing embryos, and targeted measurements of gene expression, this project will test three primary hypotheses about the developmental biology of hybrid inviability using the Caenorhabditis roundworm genus as a model system. These nematodes are ideal for this kind of study because their normal development is stereotyped and repeatable, different species will often mate with each other even though their embryos die, and the genus includes at least two species pairs that are in the process of speciating and remain partially interfertile. The study will determine when and how hybrid embryos tend to die, where and when the first defects in development appear, whether these defects are caused by abnormal cell movement or by abnormal cell fate decisions, and whether these patterns are systematic across the genus or idiosyncratic for each embryo or species pair.Statement of Merit Review,This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.