Sime Karen R, Baldwin Ian T
Department of Molecular Ecology, Max-Planck-Institute for Chemical Ecology, Jena 07745, Germany.
BMC Ecol. 2003 Jul 16;3:6. doi: 10.1186/1472-6785-3-6.
Although Nicotiana attenuata is entirely self-compatible, chemical and other floral traits suggest selection for the maintenance of advertisement for moth pollinators.
Experimental exclusions of pollinators from plants with emasculated flowers in natural populations in southern Utah during an outbreak of the hawkmoth Hyles lineata revealed that 24% of the seed set could be attributed to insect pollination, and eliminated wind pollination and apomixis as contributing to seed set. Hence these moths can mediate gene flow when self-pollen is unavailable. To quantify gene flow when self-pollen is available, plants were transformed with two marker genes: hygromycin-B resistance and beta-glucuronidase. The utility of these genetic markers to measure gene flow between plants was examined by mixing pollen from plants homozygous for both genes with self-pollen in different ratios and hand-pollinating emasculated flowers of plants growing in a natural population. The proportion of transformed seeds was positively correlated with the amount of transformed pollen applied to stigmas. In glasshouse experiments with the hawkmoth Manduca sexta and experimental arrays of transformed and wild-type plants, pollination mediated by moths accounted for 2.5% of the seed set.
Even though moth pollination is rare and highly variable for this largely selfing plant, N. attenuata opportunistically employs a mixed-mating system.
尽管弱烟草完全自交亲和，但化学及其他花部特征表明其仍保留了对蛾类传粉者的吸引机制。
在犹他州南部烟草天蛾爆发期间，对自然种群中去雄花朵的植株进行传粉者排除实验，结果显示24%的结实率可归因于昆虫传粉，排除了风媒传粉和无融合生殖对结实的影响。因此，当自花花粉不可用时，这些蛾类可介导基因流动。为了量化自花花粉存在时的基因流动，用两个标记基因对植株进行转化：潮霉素B抗性基因和β-葡萄糖醛酸酶基因。通过将两个基因均为纯合的植株花粉与自花花粉按不同比例混合，并对自然种群中生长的去雄花朵进行人工授粉，研究了这些遗传标记在测量植株间基因流动中的效用。转化种子的比例与施加到柱头上的转化花粉量呈正相关。在温室中用烟草天蛾和转化植株与野生型植株的实验阵列进行实验，蛾类介导的传粉占结实率的2.5%。
尽管对于这种主要自交的植物而言，蛾类传粉很少且变化很大，但弱烟草仍机会性地采用了混合交配系统。
