Plant and non-plant species possess cryptochrome (CRY) photoreceptors to mediate blue light regulation of development or the circadian clock. The blue light-dependent homooligomerization of Arabidopsis CRY2 is a known early photoreaction necessary for its functions, but the photobiochemistry and function of light-dependent homooligomerization and heterooligomerization of cryptochromes, collectively referred to as CRY photooligomerization, have not been well established. Here, we show that photooligomerization is an evolutionarily conserved photoreaction characteristic of CRY photoreceptors in plants and some non-plant species. Our analyses of the kinetics of the forward and reverse reactions of photooligomerization of Arabidopsis CRY1 and CRY2 provide a previously unrecognized mechanism underlying the different photosensitivity and photoreactivity of these two closely related photoreceptors. We found that photooligomerization is necessary but not sufficient for the functions of CRY2, implying that CRY photooligomerization is presumably accompanied by additional function-empowering conformational changes. We further demonstrated that the CRY2–CRY1 heterooligomerization plays roles in regulating functions of Arabidopsis CRYs in vivo. Taken together, these results suggest that photooligomerization is an evolutionarily conserved mechanism determining the photosensitivity and photoreactivity of plant CRYs.

植物和非植物物种拥有隐花色素（CRY）光感受器来介导蓝光对发育或生物钟的调节。拟南芥CRY2的蓝光依赖性同聚化是其功能所必需的已知早期光反应，但隐花色素的光依赖性同聚化和异聚化（统称为CRY光齐聚化）的光生物化学和功能尚未得到很好的证实。在这里，我们证明光齐聚是植物和一些非植物物种中 CRY 光感受器的进化保守的光反应特征。我们对拟南芥CRY1 和 CRY2 光齐聚化正向和反向反应动力学的分析提供了一个先前未被认识的机制，该机制是这两种密切相关的光感受器的不同光敏性和光反应性的基础。我们发现光齐聚对于 CRY2 的功能是必要的，但还不够，这意味着 CRY 光齐聚可能伴随着额外的功能增强构象变化。我们进一步证明CRY2-CRY1异源寡聚化在调节拟南芥CRY体内功能中发挥作用。综上所述，这些结果表明光齐聚是一种进化上保守的机制，决定植物 CRY 的光敏性和光反应性。