Histone variant H2A.Z mediates different aspects of chromatin function and modulates flowering responses in Arabidopsis

Highly coordinated gene expression patterns must be established for proper development and growth. The clues that shape these patterns reside in the genetic and epigenetic information encoded in DNA and chromatin. Eukaryotic chromatin possesses canonical histones and a number of histone variants that perform specialized functions and confer particular structural properties to the nucleosomes that contain them. The histone H2A family comprises several variants with H2A.Z being the most evolutionarily conserved. This variant is essential in eukaryotes and has emerged as a key player in chromatin function, performing an essential role in gene transcription and genome stability. During recent years, biochemical, genetic and genomic studies have begun to uncover the role of several ATP-dependent chromatin remodeling complexes in H2A.Z deposition and removal. These ATPase complexes are widely conserved from yeast to mammals. In Arabidopsis there are homologues for most of the subunits of these complexes, and their functions are just beginning to be unveiled.

In a special Plant Journal issue devoted to ¨Chromatin and epigenetics at the nexus between cell division, differentiation and development¨, José A. Jarillo and Manuel Piñeiro review the major contributions made in relation with the biology of the H2A.Z in plants and more specifically concerning the function of this histone variant in the transition from vegetative to reproductive development. Recent advances in the understanding of the molecular mechanisms underlying the H2A.Z-mediated modulation of the floral transition and particularly thermosensory flowering responses are discussed. The emerging picture shows that plants contain chromatin remodeling complexes related to those involved in modulating the dynamics of H2A.Z in other eukaryotes, but their precise biochemical nature remains elusive.