Nectar bacteria stimulate pollen germination and bursting to enhance their fitness
Nectar bacteria stimulate pollen germination and bursting to enhance their fitness
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DOI：
10.1101/2021.01.07.425766
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发表时间：
2021-01
期刊：
影响因子：
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通讯作者：
S. Christensen;I. Munkres;R. Vannette
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文献类型：
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作者：
S. Christensen;I. Munkres;R. Vannette
对于许多赏花者来说，花粉是非碳营养的主要来源，但花粉具有物理防御能力，使消费者难以获得营养。花蜜中的微生物几乎无处不在的花，可以达到高密度，尽管事实上，花花蜜是氮有限的，只含有非常低浓度的非碳营养素。花粉含有微量营养素和高蛋白质含量，但被一层柠檬酸外壳保护。在这里，我们报告说，一个常见的属花蜜居住的细菌，不动杆菌，利用花粉营养诱导花粉萌发和爆裂。我们使用时程萌发测定来量化不动杆菌属物种对花粉萌发和花粉爆裂的影响。与未接种的花粉相比，接种不动杆菌属的花粉在15分钟内导致发芽率增加，并在45分钟内爆裂。花粉萌发和爆发表型是密度依赖性的，低浓度的A。pollinis SCC 477在种子萌发高峰前的延迟时间较长，随后紧接着是种子爆发高峰。最后，A.花粉的生长密度几乎是可萌发花粉与不可萌发花粉的两倍，这表明它们诱导和利用萌发的能力在快速生长中起着重要作用。据我们所知，这是第一次直接测试花粉萌发的非植物生物诱导，也是诱导萌发作为营养采购方法的第一个证据，因为微生物似乎劫持了花粉通常严格控制的萌发机制。我们的研究结果表明，进一步研究微生物-花粉相互作用可以为授粉生态学的许多方面提供信息，包括花中的微生物生态学，传粉者从花粉中获取营养的机制，以及花粉萌发对植物繁殖的提示。
For many flower visitors, pollen is the primary source of non-carbon nutrition, but pollen has physical defenses that make it difficult for consumers to access nutrients. Nectar-dwelling microbes are nearly ubiquitous among flowers and can reach high densities, despite the fact that floral nectar is nitrogen limited, containing only very low concentrations of non-carbon nutrients. Pollen contains trace micronutrients and high protein content but is protected by a recalcitrant outer shell. Here, we report that a common genus of nectar-dwelling bacteria, Acinetobacter, exploits pollen nutrition by inducing pollen germination and bursting. We use time course germination assays to quantify the effect of Acinetobacter species on pollen germination and pollen bursting. Inoculation with Acinetobacter species resulted in increased germination rates within 15 minutes, and bursting by 45 minutes, as compared to uninoculated pollen. The pollen germination and bursting phenotype is density-dependent, with lower concentrations of A. pollinis SCC477 resulting in a longer lag time before the spike in germination, which is then closely followed by a spike in bursting. Lastly, A. pollinis grows to nearly twice the density with germinable pollen vs ungerminable pollen, indicating that their ability to induce and exploit germination plays an important role in rapid growth. To our knowledge, this is the first direct test of non-plant biological induction of pollen germination, as well as the first evidence of induced germination as a method of nutrient procurement, as the microbes appear to hijack the pollen’s normally tightly controlled germination mechanisms for their benefit. Our results suggest that further study of microbe-pollen interactions may inform many aspects of pollination ecology, including microbial ecology in flowers, the mechanisms of pollinator nutrient acquisition from pollen, and cues of pollen germination for plant reproduction.