Departamento de Biodiversidad y Conservación, Real Jardín Botánico (RJB), Consejo Superior de Investigaciones Científicas (CSIC), Plaza de Murillo 2, 28014-Madrid, Spain.
Área de Biodiversidad y Conservación, Universidad Rey Juan Carlos, C/ Tulipán s/n, 28933-Móstoles, Madrid, Spain.
Am J Bot. 2020 Jan;107(1):116-125. doi: 10.1002/ajb2.1414. Epub 2020 Jan 5.
Gynomonoecy is an infrequent sexual system in angiosperms, although widely represented within the Asteraceae family. Currently, the hypothesis of two nuclear loci controling gynomonoecy is the most accepted. However, the genic interactions are still uncertain. Anacyclus clavatus, A. homogamos, and A. valentinus differ in their sexual system and floral traits. Here, we investigate the inheritance of gynomonoecy in this model system to understand its prevalence in the family.
We selected six natural populations (two per species) for intra- and interspecific experimental crosses, and generated a total of 1123 individuals from the F generation, F , and backcrosses for sexual system characterization. The frequency of gynomonoecy observed for each cross was tested to fit different possible hypotheses of genic interaction. Additionally, the breeding system and the degree of reproductive isolation between these species were assessed.
Complementary epistasis, in which two dominant alleles are required for trait expression, explained the frequencies of gynomonoecy observed across all generations. The heterozygosity inferred in Anacyclus valentinus, as well as its lower and variable seed set, is congruent with its hybrid origin.
In our model system gynomonoecy is controlled by complementary epistasis of two genes. A common origin of this sexual system in Asteraceae, in which genic duplications, mutations, and hybridization between lineages played a key role, is hypothesized whereas independent evolutionary pathways and possibly diverse underlying genetic factors are suggested for gynomonoecy expression in other angiosperm families.
雌雄同体是被子植物中一种罕见的性系统，尽管在菊科中广泛存在。目前，两个核基因座控制雌雄同体的假设是最被接受的。然而，基因间的相互作用仍然不确定。 A. clavatus、A. homogamos 和 A. valentinus 在其性系统和花部特征上存在差异。在这里，我们研究了这个模型系统中雌雄同体的遗传，以了解其在家族中的普遍性。
我们选择了六个自然种群（每个物种两个）进行种内和种间实验杂交，并从 F 代、F 代和回交中总共产生了 1123 个个体，用于性系统特征描述。对每个杂交的雌雄同体频率进行了测试，以适应不同的基因间相互作用的可能假设。此外，还评估了这些物种的繁殖系统和生殖隔离程度。
互补上位性，即两个显性等位基因是表型表达所必需的，解释了所有世代中观察到的雌雄同体频率。 A. valentinus 中的杂合性，以及其较低和可变的种子设置，与其杂种起源一致。
在我们的模型系统中，雌雄同体由两个基因的互补上位性控制。假设该性系统在菊科中的共同起源是由于基因复制、突变和谱系间杂交起了关键作用，而其他被子植物科中雌雄同体的表达可能涉及独立的进化途径和可能不同的潜在遗传因素。
