Experimental and evolutionary ecological studies of pollination and reproductive systems using QTL mapping

我们开展了两个植物生殖系统的研究项目，一个是萱草的传粉系统，另一个是泽兰的性系统。黄萱草白天开花，花淡红色，无香味；黄萱草晚上开花，花黄色，有香味。H.fulva由蝴蝶和蜜蜂授粉，H.citrina由夜行蛾授粉。尽管这两个物种在花性状上有明显的差异，但它们的杂交后代是可育的，这为研究花适应不同传粉媒介的遗传背景提供了难得的机会。我们将这两个物种杂交，得到了F1和F2杂种。此外，我们还开发了用于QTL定位的微卫星标记和ESTs。遗传分析表明，开花时间差异主要受单基因控制，白天开花占优势。花青素的合成也主要由单基因决定，具有较大的表型效应。通过寻找与est花性状对比相关的候选基因，我们确定了萱草中chalcon synthase基因CHS （chalcon synthase gene）和MYB（控制花青素生物合成的转录因子）的同源基因。在一个田间杂交群体中，观察了不同传粉媒介对花性状的自然选择。各花性状的自然选择方向在不同年份之间存在波动，反映了昼夜传粉者可利用性的年波动。在紫茎泽兰项目中，研究了双病毒与紫茎泽兰有性和无性植物的协同进化。从紫茎泽兰无性植株叶片中发现卫星DNA，证实带有卫星DNA的双病毒可引起紫茎泽兰黄脉病。研究结果发表在《自然》杂志上。

We carried out two projects on plant reproductive systems one on pollination systems of Hemerocalis and the other on sexual systems of Eupatorium.While Hemerocalis fulva flowers at daytime and have reddish flowers without fragrance, a related species H.citrina flowers at night and have yellow flowers with fragrance. H.fulva is pollinated by butterflies and bees, and H.citrina is pollinated by nocturnal hawkmoths. Although the two species show conspicuous differentiation in floral traits, their hybrids are fertile, providing an extraordinary opportunity for studying genetic backgrounds of floral adaptation to different pollinators.We crossed the two species and obtained F1 and F2 hybrids. In addition, we developed microsatellite markers and ESTs for QTL mapping.Genetic analyses revealed that difference in flowering time is mostly controlled by single gene, the daytime flowering being dominant. Anthocyanin biosynthesis in petals of H.fulva is also determined mostly by single gene with a large phenotypic effect.By searching candidate genes responsible for the contrasting floral traits among ESTs, we determined homologues of CHS (chalcon synthase gene) and MYB (transcription factor controlling anthocyanin biosynthesis) in Hemerocalis.In a hybridizing population of H.fulva and H.citrina in the field, we observed natural selection on floral traits by various pollinators during four years. Reflecting yearly fluctuation of availability of diurnal and nocturnal pollinators, direction of natural selection on various floral traits fluctuated between years.In the Eupatorium project, coevolution between geminiviruses and sexual and asexual plants of Eupatorium was studied. We discovered satellite DNA from leaves of asexual plants of Eupatorium and confirmed that geminivirus with satellite DNA can cause yellow vein disease in Eupatorium. The result is published on Nature.