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Author(s): Bosl Noh [1, 2]; Anindita Bandyopadhyay [2, 3]; Wendy Ann Peer [3]; Edgar P. Spalding (corresponding author) [1]; Angus S. Murphy [3] Many aspects of plant growth and development [...]

Posttranslational acetylation of histones is reversibly regulated by histone deacetylases ( HDACs). Despite the evident significance of HDACs in Arabidopsis development, the biological roles and underlying molecular mechanisms of many HDACs are yet to be elucidated., By a reverse-genetic approach, we isolated an hda9 mutant and performed phenotypic analyses on it. In order to address the role of HDA9 in flowering, genetic, molecular, and biochemical approaches were employed., hda9 flowered early under noninductive short-day ( SD) conditions and had increased expression of the floral integrator FLOWERING LOCUS T ( FT) and the floral activator AGAMOUS- LIKE 19 ( AGL19) compared with the wild-type. The hda9 mutation increased histone acetylation and RNA polymerase II occupancy at AGL19 but not at FT during active transcription, and the HDA9 protein directly targeted AGL19. AGL19 expression was higher under SD than under inductive long-day (LD) conditions, and an AGL19 overexpression caused a strong up-regulation of FT. A genetic analysis showed that an agl19 mutation is epistatic to the hda9 mutation, masking both the early flowering and the increased FT expression of hda9., Taken together, our data indicate that HDA9 prevents precocious flowering under SD conditions by curbing the hyperactivation of AGL19, an upstream activator of FT, through resetting the local chromatin environment. [ABSTRACT FROM AUTHOR]

CREB-binding protein (CBP) and its homolog p300 possess histone acetyltransferase activity and function as key transcriptional co-activators in the regulation of gene expression that controls differentiation and development in animals. However, the role of CBP/ p300-like genes in plants has not yet been elucidated. Here, we show that Arabidopsis CBP/ p300-like genes promote flowering by affecting the expression of a major floral repressor FLOWERING LOCUS C ( FLC). Although animal CBP and p300 generally function as co-activators, Arabidopsis CBP/p300-like proteins are required for the negative regulation of FLC. This CBP/p300-mediated FLC repression may involve reversible protein acetylation independent of histone modification within FLC chromatin. [ABSTRACT FROM AUTHOR]

EARLY FLOWERING 5 ( ELF5) is a single-copy gene involved in flowering time regulation in Arabidopsis. ELF5 encodes a nuclear-targeted protein that is related to the human nuclear protein containing a WW domain (Npw)38-binding protein (NpwBP). Lesions in ELF5 cause early flowering in both long days and short days. elf5 mutations partially suppress the late flowering of both autonomous-pathway mutants and FRIGIDA ( FRI)-containing lines by reducing the expression of FLOWERING LOCUS C (FLC), a floral repressor upon which many of the flowering pathways converge. elf5 mutations also partially suppress photoperiod-pathway mutants, and this, along with the ability of elf5 mutations to cause early flowering in short days, indicates that ELF5 also affects flowering independently of FLC. [ABSTRACT FROM AUTHOR]