Collaborative Research: Hybrid Seed Inviability and the Evolution of Endosperm Development in Mimulus

开花植物的种子包含两个非常重要的结构：将成为幼苗并最终长成成熟植物的胚胎和胚乳，胚乳是在胚胎生长过程中为其提供营养的组织。如果你吃了米饭，你就吃了胚乳，这是填充大部分米粒的淀粉部分。自从农业出现以来，人类选择和培育了胚乳比例更大、淀粉含量更高的种子，最终创造了我们现在所依赖的作物品种。目前，直接或间接通过动物饲料提供的胚乳约占全世界人类消耗热量的67%，改进这些品种仍然至关重要。因此，从农业和粮食安全的角度来看，胚乳的发展对人类的生存至关重要。本研究将探讨猕猴花（Mimulus属）胚乳发育的调控基因以及胚乳与胚的分子和进化相互作用。虽然没有被人类食用，但由于其生态和进化历史，Mimulus为研究胚乳和胚胎之间相互作用的进化和分子方面提供了独特的机会。由于这些相互作用调节胚乳的生长，从而调节农业品种中种子营养部分的大小，这项在Mimulus上的研究结果有望产生对人类农业生产力至关重要的发育过程的分子理解。最近的证据将亲子争夺母体资源的进化理论与控制正常种子胚乳发育的表观遗传印迹基因的进化联系起来。在倍间性杂交种中，发育中的胚乳中父本和母本等位基因表达的剂量敏感性对正常发育至关重要，破坏会导致种子流产。在二倍体物种中，这种胚胎供应的冲突是否导致了印迹基因或其目标的进化分歧，并最终导致了杂交种子的致死率，目前尚不清楚。研究人员建议通过确定胚乳发育中物种分化的遗传基础和进化机制来验证这一可能性，并导致杂交种子流产，这是Mimulus guttatus的主要隔离屏障。本研究综合了基因组学、分子遗传学和发育生物学的方法，利用高通量基因组图谱、RNA测序技术和转基因技术，阐明了古家鼠与裸家鼠杂交种子败育的遗传机制。在这样做的过程中，它研究了进化生物学家（新物种是如何形成的？）和发育生物学家（胚乳生长是如何调节的？）感兴趣的基本问题，同时解决了两者都感兴趣的问题：当母亲调节生长和发育的需求不同于她的后代时，哪些分子变化可能会迅速进化？这些问题的解答将有助于揭示开花植物胚乳发育调控过程和分化的进化机制。

The seed of flowering plants contains two very important structures: the embryo that will become a seedling and eventually grow into the mature plant, and the endosperm, a tissue that provides nutrients to the embryo as it grows. If you have eaten rice, you have eaten endosperm, the starchy portion that fills the majority of the rice grain. Since the emergence of agriculture, humans have selected and bred seeds with a larger and starchier endosperm portion, ultimately creating the crop varieties we now depend upon. Endosperm, either directly or indirectly through animal feed, now provides an estimated 67% of the calories consumed by humans worldwide, and improving on these varieties remains of fundamental importance. Thus, from both an agricultural and food security perspective the development of the endosperm is critical to humankind's survival. This research will investigate the genes that control endosperm development and the molecular and evolutionary interactions between the endosperm and the embryo in the monkey flower (genus Mimulus). Although not eaten by humans, due to its ecological and evolutionary history, Mimulus provides a unique opportunity to study evolutionary and molecular aspects of the interactions between endosperm and embryo. As these interactions regulate the growth of the endosperm and thus the size of the nutritious portion of the seed in agricultural varieties, the results of this research in Mimulus are expected to engender a molecular understanding of a developmental process critical to human agricultural productivity.Recent evidence links the evolutionary theory of parent-offspring conflict over maternal resources to the evolution of epigenetically imprinted genes controlling normal seed endosperm development. In interploidy hybrids, dosage-sensitivity of paternal and maternal allelic expression in developing endosperm is critical to normal development, and disruption leads to seed abortion. As yet it remains unknown whether such conflict over embryo provisioning leads to evolutionary divergence of imprinted genes or their targets, and ultimately hybrid seed lethality, in diploid species. The investigators propose to test this possibility by determining the genetic basis and evolutionary mechanisms underlying species divergence in endosperm development and leading to hybrid seed abortion, a principal isolating barrier in the Mimulus guttatus sp. complex. This research integrates genomic, molecular genetic and developmental biology approaches, utilizing high-throughput genome mapping, RNA sequencing technologies, and transgenic techniques to elucidate the genetic mechanisms contributing to seed abortion in M. guttatus x M. nudatus crosses. In so doing, it examines questions of fundamental interest to evolutionary biologists (how are new species formed?), and to developmental biologists (how is endosperm growth regulated?) while addressing a question of interest to both: what molecular changes might rapidly evolve when the mother's need to regulate growth and development differs from that of her offspring? Answering these questions will shed light on the developmental processes regulating endosperm growth and the evolutionary mechanisms driving divergence in flowering plants.