State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China.
Institute of Evolution and Ecology, School of Life Sciences, Central China Normal University, Wuhan, China.
Plant Biol (Stuttg). 2019 Jul;21(4):732-737. doi: 10.1111/plb.12957. Epub 2019 Feb 4.
It has been hypothesised that intense metabolism of nectar-inhabiting yeasts (NIY) may change nectar chemistry, including volatile profile, which may affect pollinator foraging behaviours and consequently plant fitness. However, empirical evidence for the plant-microbe-pollinator interactions remains little known. To test this hypothesis, we use a bumblebee-pollinated vine Clematis akebioides endemic to southwest China as an experimental model plant. To quantify the incidence and density of Metschnikowia reukaufii, a cosmopolitan NIY in floral nectar, a combination of yeast cultivation and microscopic cell-counting method was used. To examine the effects of NIY on plant-pollinator interactions, we used real flowers filled with artificial nectar with or without yeast cells. Then the volatile metabolites produced in the yeast-inoculated nectar were analysed with coupled gas chromatography and mass spectrometry (GC-MS). On average 79.3% of the C. akebioides flowers harboured M. reukaufii, and cell density of NIY was high to 7.4 × 10 cells mm . In the field population, the presence of NIY in flowers of C. akebioides increased bumblebee (Bombus friseanus) pollinator visitation rate and consequently seed set per flower. A variety of fatty acid derivatives produced by M. reukaufii may be responsible for the above beneficial interactions. The volatiles produced by the metabolism of M. reukaufii may serve as an honest signal to attract bumblebee pollinators and indirectly promote the female reproductive fitness of C. akebioides, forming a potentially tripartite plant-microbe-pollinator mutualism.
据推测，花蜜中酵母（NIY）的高强度代谢可能会改变花蜜的化学性质，包括挥发性成分，这可能会影响传粉者的觅食行为，从而影响植物的适合度。然而，有关植物-微生物-传粉者相互作用的实证证据仍然知之甚少。为了验证这一假设，我们以中国西南特有的熊蜂授粉藤本Clematis akebioides 作为实验模型植物。为了量化普遍存在于花蜜中的 Metschnikowia reukaufii 的发病率和密度，我们采用了酵母培养和显微镜细胞计数法的组合方法。为了研究 NIY 对植物-传粉者相互作用的影响，我们使用了充满人工花蜜和酵母细胞的真花。然后，用气相色谱和质谱联用仪（GC-MS）分析了在酵母接种的花蜜中产生的挥发性代谢物。平均而言，79.3%的 C. akebioides 花朵中存在 M. reukaufii，NIY 的细胞密度高达 7.4×10 个细胞 mm。在野外种群中，C. akebioides 花朵中存在 NIY 会增加熊蜂（Bombus friseanus）传粉者的访问率，从而提高每朵花的结实率。M. reukaufii 产生的各种脂肪酸衍生物可能是导致上述有益相互作用的原因。M. reukaufii 代谢产生的挥发性物质可能作为吸引熊蜂传粉者的诚实信号，并间接促进 C. akebioides 的雌性生殖适合度，形成潜在的三方植物-微生物-传粉者共生关系。
