SWR1 Chromatin Remodeling Complex: A Key Transcriptional Regulator in Plants

Abstract

The nucleosome is the structural and fundamental unit of eukaryotic chromatin. The chromatin remodeling complexes change nucleosome composition, packaging and positioning to regulate DNA accessibility for cellular machinery. SWI2/SNF2-Related 1 Chromatin Remodeling Complex (SWR1-C) belongs to the INO80 chromatin remodeling family and mainly catalyzes the exchange of H2A-H2B with the H2A.Z-H2B dimer. The replacement of H2A.Z into nucleosomes affects nucleosome stability and chromatin structure. Incorporation of H2A.Z into the chromatin and its physiochemical properties play a key role in transcriptional regulation during developmental and environmental responses. In Arabidopsis, various studies have uncovered several pivotal roles of SWR1-C. Recently, notable progress has been achieved in understanding the role of SWR1-C in plant developmental and physiological processes such as DNA damage repair, stress tolerance, and flowering time. The present article introduces the SWR1-C and comprehensively reviews recent discoveries made in understanding the function of the SWR1 complex in plants.

Keywords: SWR1-C, H2A.Z; chromatin remodeling complex; flowering time regulation.

Figure 1

Schematic representation of SWI2/SNF2-Related 1 Chromatin Remodeling Complex (SWR1-C) mediated chromatin remodeling and swapping of H2A-H2B with the H2A.Z-H2B dimer, resulting in repressive and active chromatin state.

Figure 2

Regulation of flowering time in Arabidopsis. FLOWERING LOCUS C (FLC), plays a key role in flowering time induction by acting as a repressor of flowering. The expression of FLC is regulated by FRIGIDA, vernalization, autonomous pathways, and SWR1-C. FLC restricts flowering by directly repressing the key genes responsible for flowering including FLOWERING LOCUS T (FT), FD, and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1). The vernalization pathway promotes flowering in response to the prolonged exposure to cold temperature by turning off the FLC. Flowering can also be induced by age, photoperiod, and Gibberellic acid (GA). The photoperiod promotes flowering in response to day length. Additionally, miR156/miR172 also play a critical function in phase change by targeting the transcription factors SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) and APETALA2 (AP2) like genes.