The evolutionary landscape of PRC1 core components in green lineage

Abstract

The origin and evolution of plant PRC1 core components. Polycomb repressive complex1 (PRC1) plays critical roles in epigenetic silencing of homeotic genes and determination of cell fate. Animal PRC1 has been well investigated for a long time, whereas plant PRC1 was just confirmed in recent years. It is enigmatic whether PRC1 core components in plants share a common ancestor with those in animals. We evaluated the origin of plant PRC1 RING-finger proteins (RING1 and BMI1) through comparing with the homologs in some representative unikonts and using BMI1- and RING1-like proteins as reciprocal outgroup, finding both PRC1 RING-finger proteins have the earliest origin in mosses, similar to LHP1. Additionally, the gene structure, copy number, and domain organization were analyzed to deeply understand the evolutionary history of plant PRC1 complex. In conclusion, PRC1 RING-finger proteins have independent origins in plants and animals, but convergent evolution might attribute to the conservation of PRC1 complex in plants and animals. Plant LHP1 as the homolog of non-PRC1 protein HP1 was recruited to fulfill the role of Pc counterpart. Gene duplication followed by functional divergence makes a great contribution to evolutionary progress of PRC1 in green plants.

Characterization of the Polycomb-Group Mark H3K27me3 in Unicellular Algae

“…In contrast, the RING1 subunit is widely conserved, suggesting a mono-ubiquitylation activity unrelated to PRC1 in algae and protein moonlighting (Jeffery, 2003). In general, an abundance of RING1 homologs in chlorophytes, but the absence of other PRC1 components in lower branches of Archaeplastida used here is consistent with the previous studies (Hennig and Derkacheva, 2009; Berke and Snel, 2015; Chen et al, 2016) and agrees with the notion of lower PRC1 conservation and potential loss of the complex in several phylogenetic branches.…”

“…Core PRC1 complex in model flowering plant Arabidopsis thaliana consist of AtRING1a/b (equivalent to dRING/Sce), AtBMI1a/b/c and EMF1 (equivalent to Psc), and LHP1 (equivalent to Pc). Although a wide range of PRC1-associated proteins exists (Chen et al, 2016), it is unclear how the combinations of different subunits depend on specific temporal and spatial conditions. In contrast to PRC1, composition of the Arabidopsis PRC2 complex is better characterized.…”

The genetic basis for PRC1 complex diversity emerged early in animal evolution

“…In Drosophila, in addition to the canonical complex outlined above, two non-canonical PRC1 complexes have been described: dRAF, which contains KDM2, a lysine demethylase subunit (57), and a complex which contains an alternative Psc homolog (58). PRC1 complexes containing RING1/2 and PCGF proteins are present in plants, but many of the other components in these complexes are distinct to those in animals (59)(60)(61)(62). Similarly, RING1/2 and PCGF are encoded in the genomes of many unicellular eukaryotes like choanoflagellates, ichthyosporeans, and filasterians (1), but it is not known whether they form complexes with PRC1-like functions.…”

Identification of Polycomb Repressive Complex 1 and 2 Core Components in Hexaploid Bread Wheat

“…2007). A. thaliana B LYMPHOMA Mo-MLV INSERTION REGION 1 HOMOLOG ( AtBMI1A to C ) are three homologs of Psc, and REALLY INTERESTING NEW GENE1 ( AtRING1A and AtRING1B ) are two homologs of Sce (reviewed in (Chen et al . 2016)).…”