Question: What is the role of histone variant H2A.W?

Context:
The histone variant H2A.W defines heterochromatin and promotes chromatin condensation in Arabidopsis
The histone variant H2A.W marks heterochromatin specifically and acts in synergy with heterochromatic marks H3K9me2 and DNA methylation to maintain transposon silencing
In vitro, H2A.W enhances chromatin condensation by promoting fiber-to-fiber interactions via its conserved C-terminal motif. In vivo, H2A.W is required for heterochromatin condensation, demonstrating that H2A.W plays critical roles in heterochromatin organization.
 In non-flowering land plants, we identify a new class of H2A variants and propose their possible role in the emergence of the H2A.W variant class in flowering plants
Covalent histone modifications (e.g. ubiquitination, phosphorylation, methylation, acetylation) and H2A variants (H2A.Z, H2A.X and H2A.W) are also discussed in view of their crucial importance in modulating nucleosome organization and function.
The histone variant H2A.W defines heterochromatin and promotes chromatin condensation in Arabidopsis.
In vivo, H2A.W is required for heterochromatin condensation, demonstrating that H2A.W plays critical roles in heterochromatin organization. 
In vivo, H2A.W is required for heterochromatin condensation, demonstrating that H2A.W plays critical roles in heterochromatin organization.
The histone variant H2A.W defines heterochromatin and promotes chromatin condensation in Arabidopsis.
Similarities in conserved motifs between H2A.W and another H2A variant in metazoans suggest that plants and animals share common mechanisms for heterochromatin condensation..
In vitro, H2A.W enhances chromatin condensation by promoting fiber-to-fiber interactions via its conserved C-terminal motif.

Answer: The histone variant H2A.W defines heterochromatin and promotes chromatin condensation in Arabidopsis. The histone variant H2A.W marks heterochromatin specifically and acts in synergy with heterochromatic marks H3K9me2 and DNA methylation to maintain transposon silencing. In vivo, H2A.W is required for heterochromatin condensation, demonstrating that H2A.W plays critical roles in heterochromatin organization. In vitro, H2A.W enhances chromatin condensation by promoting fiber-to-fiber interactions via its conserved C-terminal motif. In non-flowering land plants, we identify a new class of H2A variants and propose their possible role in the emergence of the H2A.W variant class in flowering plants. 
The histone variant H2A.W defines heterochromatin and promotes chromatin condensation in Arabidopsis The histone variant H2A.W marks heterochromatin specifically and acts in synergy with heterochromatic marks H3K9me2 and DNA methylation to maintain transposon silencing In vitro, H2A.W enhances chromatin condensation by promoting fiber-to-fiber interactions via its conserved C-terminal motif. In vivo, H2A.W is required for heterochromatin condensation, demonstrating that H2A.W plays critical roles in heterochromatin organization.  In non-flowering land plants, we identify a new class of H2A variants and propose their possible role in the emergence of the H2A.W variant class in flowering plants Covalent histone modifications (e.g.
The histone variant H2A.W marks heterochromatin specifically and acts in synergy with heterochromatic marks H3K9me2 and DNA methylation to maintain transposon silencing. In vivo, H2A.W is required for heterochromatin condensation, demonstrating that H2A.W plays critical roles in heterochromatin organization. Histone chaperones escort histones, and play key functions during nucleosome assembly/disassembly and in nucleosome structure configuration. Here we focus on plant histone H2A/H2B chaperones, particularly members of the NUCLEOSOME ASSEMBLY PROTEIN-1 (NAP1) and FACILITATES CHROMATIN TRANSCRIPTION (FACT) families, discussing their molecular features, properties, regulation and function. We further discuss roles of NAP1 and FACT in chromatin-based processes, such as transcription, DNA replication and repair. Future major challenges remain in order to define in more detail the overlapping and specific roles of various members of the NAP1 family as well as differences and similarities between NAP1 and FACT family members, and to identify and characterize their partners as well as new families of chaperones to understand histone variant incorporation and chromatin target specificity.
 In non-flowering land plants, we identify a new class of H2A variants and propose their possible role in the emergence of the H2A.W variant class in flowering plants In vitro, H2A.W enhances chromatin condensation by promoting fiber-to-fiber interactions via its conserved C-terminal motif. In vivo, H2A.W is required for heterochromatin condensation, demonstrating that H2A.W plays critical roles in heterochromatin organization.
The histone variant H2A.W defines heterochromatin and promotes chromatin condensation in Arabidopsis
Histone variants play crucial roles in gene expression, genome integrity, and chromosome segregation. The histone variant H2A.W marks heterochromatin specifically and acts in synergy with heterochromatic marks H3K9me2 and DNA methylation to maintain transposon silencing. In vivo, H2A.W is required for heterochromatin condensation, demonstrating that H2A.W plays critical roles in heterochromatin organization. Histone chaperones escort histones, and play key functions during nucleosome assembly/disassembly and in nucleosome structure configuration. Covalent histone modifications (e.g. ubiquitination, phosphorylation, methylation, acetylation) and H2A variants (H2A.Z, H2A.X and H2A.W) are also discussed in view of their crucial importance in modulating nucleosome organization and function.
The histone variant H2A.W marks heterochromatin specifically and acts in synergy with heterochromatic marks H3K9me2 and DNA methylation to maintain transposon silencing. In vitro, H2A.W enhances chromatin condensation by promoting fiber-to-fiber interactions via its conserved C-terminal motif. In vivo, H2A.W is required for heterochromatin condensation, demonstrating that H2A.W plays critical roles in heterochromatin organization.