Extended Data Fig. 1: Comparison of the domain architecture of Ia bHLHs in land plants.

a, A diagram of the domain architecture of MpSETA (M. polymorpha), PpSMF1, PpSMF2 (P. patens), AtSPCH, AtMUTE, and AtFAMA (A. thaliana). While no PEST domain was identified, MpSETA has a bHLH domain and SMF domain conserved at the C-terminus like other Ia bHLH proteins. SMF domain is structurally considered to be the ACT-like domain, which is a putative domain for protein-protein dimerization. b, Sequence alignment of the bHLH domain of Ia bHLH proteins. Ia bHLHs are surrounded by a black box, and others are Ib(1) bHLHs. Asterisks indicate amino acids that are assumed to be important for binding to the E-box (CANNTG), and the triangles indicate amino acids that are assumed to be important for the dimerization of the bHLH domain. The yellow box indicates the LxCxE motif, which is a binding motif with Retinoblastoma-related (RBR). c, Sequence alignment of the C-terminal SMF domain of Ia bHLH proteins.