PMID:23273925

Citation	Xiao, J, Zhang, H, Xing, L, Xu, S, Liu, H, Chong, K and Xu, Y (2013) Requirement of histone acetyltransferases HAM1 and HAM2 for epigenetic modification of FLC in regulating flowering in Arabidopsis. J. Plant Physiol. 170:444-51
Abstract	Histone acetylation is an important posttranslational modification associated with gene activation. In Arabidopsis, two MYST histone acetyltransferases HAM1 and HAM2 work redundantly to acetylate histone H4 lysine 5 (H4K5ace) in vitro. The double mutant ham1/ham2 is lethal, which suggests the critical role of HAM1 and HAM2 in development. Here, we used an artificial microRNA (amiRNA) strategy in Arabidopsis to uncover a novel function of HAM1 and HAM2. The amiRNA-HAM1/2 transgenic plants showed early flowering and reduced fertility. In addition, they responded normally to photoperiod, gibberellic acid treatment, and vernalization. The expression of flowering-repressor FLOWERING LOCUS C (FLC) and its homologues, MADS-box Affecting Flowering genes 3/4 (MAF3/4), were decreased in amiRNA-HAM1/2 lines. HAM1 overexpression caused late flowering and elevated expression of FLC and MAF3/4. Mutation of FLC almost rescued the late flowering with HAM1 overexpression, which suggests that HAM1 regulation of flowering time depended on FLC. Global H4 acetylation was decreased in amiRNA-HAM1/2 lines, but increased in HAM1-OE lines, which further confirmed the acetyltransferase activity of HAM1 in vivo. Chromatin immunoprecipitation revealed that H4 hyperacetylation and H4K5ace at FLC and MAF3/4 were less abundant in amiRNA-HAM1/2 lines than the wild type, but were enriched in HAM1-OE lines. Thus, HAM1 and HAM2 may affect flowering time by epigenetic modification of FLC and MAF3/4 chromatins at H4K5 acetylation.
Links	PubMed Online version:10.1016/j.jplph.2012.11.007
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ARATH:MYST1		GO:2000028: regulation of photoperiodism, flowering	ECO:0000315:		P		Figure 1C shows that amiRNA-HAM1 (HAM1 knockdown) lines grew normally as the wild-type Col in the vegetative stage, but flowered earlier than Col under both LD and SD conditions. Figure 3B demonstrates that HAM1-overexpressing transgenic plants (HAM1-OE) displayed a delayed flowering time phenotype compared to wild type, suggesting that HAM1 is a negative regulator of flowering.	complete CACAO 8182
ARATH:MYST1		GO:0043995: histone acetyltransferase activity (H4-K5 specific)	ECO:0000315:		F		Figure 5A shows a Western blot analysis in amiRNA-HAM1 (HAM1 knockdown) lines compared to wildtype that demonstrates a significant decrease in global H4K5 acetylation. In contrast, H4K5 acetylation was significantly increased in HAM1-OE (over-expressed) lines.	complete CACAO 8183
ARATH:MYST1	involved_in	GO:2000028: regulation of photoperiodism, flowering	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete
ARATH:MYST1	enables	GO:0043995: histone acetyltransferase activity (H4-K5 specific)	ECO:0000315: mutant phenotype evidence used in manual assertion		F		Seeded From UniProt	complete

References

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