The cycling DOF factors of the moss Physcomitrium patens can form a heterodimer in yeast

The model angiosperm Arabidopsis thaliana uses cycling DOF factors (CDFs) to regulate sexual reproduction in response to seasonal cues such as daylength and temperature. The stability of CDFs is regulated by FKF-1, a three-domain protein containing a LOV domain, an F-box, and six Kelch repeats. Physcomitrium patens, a moss that shared a common ancestor with A. thaliana 450 million years ago, possesses CDF-like proteins and partial homologs of FKF-1, including two twin-LOV proteins and two F-box/Kelch proteins. Given this conservation and the conservation of the FKF-1 binding domain in two P. patens CDF-like proteins, we tested if P. patens FKF-1 partial homologs can form a complex similar to FKF-1 in A. thaliana, and if the CDF-like proteins can interact with any of the FKF-1 partial homologs. We used a yeast two-hybrid system to test for pairwise interactions between five proteins. We did not observe interaction between the CDF-like proteins and the FKF-1 partial homologs, nor between the partial homologs themselves. We did, however, observe interaction between the two CDF-like proteins to form a heterodimer, which could play a role in the function or regulation of the CDFs.