Interactions between MADS box transcription factors are critical in the regulation of floral development, and shifting MADS box protein-protein interactions are predicted to have influenced floral evolution. However, precisely how evolutionary variation in protein-protein interactions affects MADS box protein function remains unknown. To assess the impact of changing MADS box protein-protein interactions on transcription factor function, we turned to the grasses, where interactions between B-class MADS box proteins vary. We tested the functional consequences of this evolutionary variability using maize (Zea mays) as an experimental system. We found that differential B-class dimerization was associated with subtle, quantitative differences in stamen shape. In contrast, differential dimerization resulted in large-scale changes to downstream gene expression. Differential dimerization also affected B-class complex composition and abundance, independent of transcript levels. This indicates that differential B-class dimerization affects protein degradation, revealing an important consequence for evolutionary variability in MADS box interactions. Our results highlight complexity in the evolution of developmental gene networks: changing protein-protein interactions could affect not only the composition of transcription factor complexes but also their degradation and persistence in developing flowers. Our results also show how coding change in a pleiotropic master regulator could have small, quantitative effects on development.

MADS 盒转录因子之间的相互作用对于花发育的调节至关重要，并且 MADS 盒蛋白质-蛋白质相互作用的变化预计会影响花的进化。然而，蛋白质-蛋白质相互作用的进化变异究竟如何影响 MADS 盒蛋白功能仍然未知。为了评估改变 MADS 盒蛋白-蛋白质相互作用对转录因子功能的影响，我们以草为对象，其中 B 类 MADS 盒蛋白之间的相互作用各不相同。我们使用玉米（ Zea mays）测试了这种进化变异性的功能后果）作为实验系统。我们发现差异 B 类二聚化与雄蕊形状的细微数量差异相关。相反，差异二聚化导致下游基因表达发生大规模变化。差异二聚化还影响 B 类复合物的组成和丰度，与转录水平无关。这表明差异 B 类二聚化影响蛋白质降解，揭示了 MADS 盒相互作用的进化变异性的重要结果。我们的结果强调了发育基因网络进化的复杂性：改变蛋白质-蛋白质相互作用不仅会影响转录因子复合物的组成，还会影响它们在发育过程中的降解和持久性。