| Gene/protein | Evidence type | Key findings | Quantitative data | Phenotypes | Source |
|---|---|---|---|---|---|
| **Mez1 / EZ1 / ZmMEZ1** | Expression, comparative genomics, epigenomic inference | One of three maize **E(z)** homologs in PRC2; **imprinted** and most closely related to Arabidopsis **CLF**; expressed in endosperm and other tested tissues; proposed to contribute to endosperm functions and H3K27me3 deposition as a PRC2 catalytic subunit by homology/inference. In developing endosperm, **ZmMEZ1** is highly expressed together with **ZmFie1, ZmEmf2b, ZmMSI1c**, supporting participation in a grain-filling PRC2 complex. | H3K27me3 marks nearly all maize PEGs in endosperm: **41/46 (89%)**; in 3 tested cases the mark was maternal-allele restricted. During grain filling, intersecting dynamic peaks yielded **5923** common peaks (FSPs) mapping to **2838** genes; **7084** new H3K27me3 peaks were identified at **20 DAP**. | No direct maize **mez1** mutant phenotype reported in retrieved papers; no exon-insertion line recovered for Mez1 in the 2013 study. Functional role is strongest in **endosperm/grain filling** by expression-context evidence rather than direct genetics. (pqac-00000009, pqac-00000011, pqac-00000012, pqac-00000014) | Makarevitch et al., 2013, *Plant Cell*, https://doi.org/10.1105/tpc.112.106427, doi:10.1105/tpc.112.106427; Wang et al., 2025, *Plant Communications*, https://doi.org/10.1016/j.xplc.2025.101343, doi:10.1016/j.xplc.2025.101343 |
| **Mez2** | Genetic, epigenomic, transcript, mutant analysis | Maize **E(z)** homolog and putative H3K27me3 methyltransferase; partially redundant with **Mez3** for maintaining H3K27me3 at a subset of loci. Single and double mutant profiling shows only part of the maize H3K27me3 landscape depends on Mez2/3, indicating redundancy and additional methyltransferase activity from other E(z) family members. | In B73, **4374** H3K27me3-enriched segments were detected; **742 (17%)** were **Mez2/3-dependent**, including **21** mez2-only, **315** mez3-only, **90** double-mutant-only, and **316** affected by either mutation; **659** filtered-gene-set genes lay in Mez2/3-dependent regions. | Homozygous **mez2** single mutants and **mez2 mez3** double mutants had **no striking morphological defects**; plants were somewhat smaller but fertile, and RNA-seq found no broad enrichment of expression changes among Mez2/3-dependent targets. (pqac-00000006, pqac-00000015, pqac-00000016, pqac-00000018) | Makarevitch et al., 2013, *Plant Cell*, https://doi.org/10.1105/tpc.112.106427, doi:10.1105/tpc.112.106427 |
| **Mez3** | Genetic, epigenomic, transcript, mutant analysis | Highly similar paralog of **Mez2** (92% nucleotide identity) and more closely related to Arabidopsis **SWN/MEA**; contributes to H3K27me3 maintenance with stronger locus-specific impact than Mez2 in the reported mutant series. Supports the model that maize PRC2 catalytic activity is partitioned among multiple E(z)-like proteins. | Same mutant dataset as above: among the **742** Mez2/3-dependent H3K27me3 segments, **315** were **mez3-only dependent** versus **21** mez2-only, indicating a larger unique contribution from Mez3 in this dataset. Across tissues, H3K27me3-marked genes were highly dynamic: **40.6%** marked in only one tissue, **21%** in two tissues, and **8.2%** in all five tissues. | **mez3** mutants were viable and fertile with only mild size reduction; no major developmental abnormality reported despite local H3K27me3 losses. (pqac-00000008, pqac-00000015, pqac-00000018) | Makarevitch et al., 2013, *Plant Cell*, https://doi.org/10.1105/tpc.112.106427, doi:10.1105/tpc.112.106427 |
| **Mez1/Mez2/Mez3 family (maize E(z) homologs)** | Family-level comparative/epigenomic evidence | The maize genome encodes **three E(z) homologs** that are the likely catalytic PRC2 subunits responsible for histone **H3 Lys-27 methylation**, especially **H3K27me3**. Mez1 is the imprinted member; Mez2/Mez3 are paralogous SWN/MEA-like genes. Family-level evidence links these proteins to chromatin repression, imprinting, and developmental regulation in maize. | Genome-wide catalogs identified **6337** filtered H3K27me3-marked genes in at least one of five B73 tissues, **5690** in four diploid tissues, and **12,266** methylated genes overall. H3K27me3 covered **0.13%–1.91%** of the genome depending on tissue, and ~**16%** of filtered-gene-set genes were marked in at least one tissue. Conservation statistics: **34%** of maize H3K27me3 targets with Arabidopsis orthologs were also marked in Arabidopsis; conservation with rice was **64%** for seedling-marked genes and **74%** for genes marked in all five tissues. | Family-level mutant evidence indicates mild visible phenotypes for **mez2/mez3**, suggesting redundancy and/or context-specific importance; strongest biological association is with **endosperm imprinting** and **grain-filling regulation**. (pqac-00000008, pqac-00000013, pqac-00000016, pqac-00000017) | Makarevitch et al., 2013, *Plant Cell*, https://doi.org/10.1105/tpc.112.106427, doi:10.1105/tpc.112.106427 |
| **ZmMEZ1 within Fie1-PRC2 endosperm complex** | Expression, developmental epigenomics | Recent cereal endosperm work places **ZmMEZ1** in a maize **PRC2** module with **ZmFie1, ZmEmf2b, ZmMSI1c** at the onset of grain filling; expression patterns suggest a **ZmFie1-mediated PRC2** is the primary regulator during **En6D–En10D**, linking ZmMEZ1 to developmental H3K27me3 deposition during kernel filling. | Peak dynamics during endosperm development: **8365** peaks gained (8 vs 6 DAP), **12,111** peaks lost (12 vs 10 DAP), overlap **5923** peaks, corresponding to **2838** genes; additional gene sets included **1140** B8 gain-only and **3884** B12 loss-only genes. | Supports a role in balancing **endosperm filling and development**; phenotype in this excerpt is developmental-stage regulation rather than direct ZmMEZ1 mutant analysis. (pqac-00000011, pqac-00000014) | Wang et al., 2025, *Plant Communications*, https://doi.org/10.1016/j.xplc.2025.101343, doi:10.1016/j.xplc.2025.101343 |


*Table: This table summarizes the strongest available evidence for maize Enhancer of zeste-like genes, especially Mez1/EZ1 and Mez2/Mez3, integrating genetic, epigenomic, and expression findings. It is useful for distinguishing direct maize evidence from family-level inference and for tracking the quantitative H3K27me3 data tied to each gene.*