Division of Mechatronics, Biostatistics, and Sensors, KU Leuven, 3001, Leuven, Belgium.
Centre for Microbial and Plant Genetics, KU Leuven, 3001, Leuven, Belgium.
ISME J. 2022 Oct;16(10):2305-2312. doi: 10.1038/s41396-022-01275-y. Epub 2022 Jul 1.
In Saccharomyces cerevisiae, the FLO1 gene encodes flocculins that lead to formation of multicellular flocs, that offer protection to the constituent cells. Flo1p was found to preferentially bind to fellow cooperators compared to defectors lacking FLO1 expression, enriching cooperators within the flocs. Given this dual function in cooperation and kin recognition, FLO1 has been termed a "green beard gene". Because of the heterophilic nature of the Flo1p bond however, we hypothesize that kin recognition is permissive and depends on the relative stability of the FLO1/flo1 versus FLO1/FLO1 detachment force F. We combine single-cell measurements of adhesion, individual cell-based simulations of cluster formation, and in vitro flocculation to study the impact of relative bond stability on the evolutionary stability of cooperation. We identify a trade-off between both aspects of the green beard mechanism, with reduced relative bond stability leading to increased kin recognition at the expense of cooperative benefits. We show that the fitness of FLO1 cooperators decreases as their frequency in the population increases, arising from the observed permissive character (F = 0.5 F) of the Flo1p bond. Considering the costs associated with FLO1 expression, this asymmetric selection often results in a stable coexistence between cooperators and defectors.
在酿酒酵母中，FLO1 基因编码絮凝蛋白，导致多细胞絮凝的形成，为组成细胞提供保护。与缺乏 FLO1 表达的缺陷体相比，Flo1p 被发现优先与合作者结合，从而在絮凝物中富集合作者。鉴于 FLO1 在合作和亲属识别中的双重功能，FLO1 被称为“绿须基因”。然而，由于 Flo1p 键的异质性质，我们假设亲属识别是允许的，并且取决于 FLO1/flo1 与 FLO1/FLO1 分离力 F 的相对稳定性。我们结合单细胞粘附测量、基于单个细胞的簇形成模拟以及体外絮凝来研究相对键稳定性对合作进化稳定性的影响。我们确定了绿须机制的两个方面之间的权衡，降低相对键稳定性会导致亲属识别增加，而合作收益则会降低。我们表明，随着 FLO1 合作者在种群中的频率增加，它们的适应性会降低，这是由于观察到 Flo1p 键的许可特征（F=0.5F）。考虑到与 FLO1 表达相关的成本，这种不对称选择通常会导致合作者和缺陷体之间的稳定共存。
