PDF《Plants》

1 To whom correspondence should be addressed. E-mail kewu@ ntu.edu.tw, tel. 886-2-33664546, fax 886-2-33663738.

2 These authors contributed equally to this work. ? The Author 2014. Published by the Molecular Plant Shanghai Editorial Office in association with Oxford University Press on behalf of CSPB and IPPE, SIBS, CAS. doi:10.1093/mp/ssu033, Advance Access publication

21 March

2014 Received

25 January 2014;

accepted

18 March

2014 765 Histone Deacetylases and Gene Repression 2006), while members of the RPD3/HDA1 superfamily share sequence homology in the HDAC domain and require Zn2+ cofactor for deacetylase activity (Yang and Seto, 2007). In addition, HD2 proteins are plant-specific HDACs (Pandey et?al., 2002). HISTONE DEACETYLASES IN?PLANTS In the past decade, plant HDACs have drawn considerable research attention and an increasing number of HDACs were identified and characterized from Arabidopsis, rice, and other plant species. Among

18 HDACs indentified in Arabidopsis,

12 of them belong to the RPD3/HDA1 super- family (Hollender and Liu, 2008;

Alinsug et? al., 2009). Based on sequence similarity, the RPD3/HDA1 superfam- ily are further divided into three classes. Class?I?has four members: HDA19, HDA6, HDA7, and HDA9, representing the functionally best-characterized HDACs in Arabidopsis. Class?II includes HDA5, HDA15, and HDA18. HDA2 and its two additional isoforms comprise class?III. HDA8, HDA14, HDA10, and HDA17 are unclassified members of the RPD3- like superfamily (Pandey et? al., 2002;

Hollender and Liu, 2008). Characterization of HDAC mutants in Arabidopsis indicated that the members of the RPD3/HDA1 family HDACs play a vital role in regulating gene expression in various biological processes. For instance, HDA6 mutant alleles, axe1-1 and axe1-5, displayed increased expression of the auxin-responsive reporter genes (Murfett et?al., 2001). Another HDA6 allele, rst1, was shown to have reduced DNA methylation in centromeric and rDNA repeats, indicating that HDA6 may act to maintain DNA methylation (Aufsatz et?al., 2002), while HDA19, the closest homolog of HDA6, was shown to be important for proper vegetative develop- ment as hda19 mutants displayed various developmental abnormalities (Tian and Chen, 2001;

Tian et?al., 2005;

Zhou et?al., 2005;

Long et?al., 2006). Loss-of-function of HDA18 resulted in alterations in the cellular patterning in the root epidermis in Arabidopsis (Xu et?al., 2005;

Liu et?al., 2013a). In addition, HDA7 is crucial for female gametophyte devel- opment and embryogenesis in Arabidopsis (Cigliano et?al., 2013). Furthermore, HDA14 is an α-tubulin decetylase asso- ciated with α/β-tubulin and enriched in microtubule frac- tions by direct association with the PPP-type phosphatases PP2A (Tran et?al., 2012). Arabidopsis has four members of the plant-spe- cific HD2 family proteins, namely HD2A/HDT1, HD2B/ HDT2, HD2C/HDT3, and HD2D/HDT4. Silencing of HD2A in Arabidopsis resulted in aborted seed development (Wu et?al., 2000), while overexpression of HD2A caused morphological defects of leaves and flowers as well as delayed flowering and aborted seed development (Zhou et?al., 2004). HD2A and HD2B were found to act inde- pendently with ASYMMETRIC LEAVES1 (AS1) and AS2 to control miR165/166 distribution and the develop- ment of adaxialCabaxial leaf polarity (Ueno et?al., 2007). Furthermore, HD2A also functions in the postembryonic establishment of nucleolar dominance (Pontes et? al., 2007). The function of SIR2 family HDACs was also been inves- tigated in Arabidopsis. The Arabidopsis genome encodes two SIR2 family HDACs: SRT1 and SRT2. SRT2 resides pre- dominantly at the inner mitochondrial membrane and interacts with a small number of protein complexes mainly involved in energy metabolism and metabolite trans- port (Koenig et?al., 2014). Further analysis indicated that SRT2 plays an important role in fine-tuning mitochondrial energy metabolism. Compared to Arabidopsis, relatively few HDACs were characterized in other plant species. HD2-type HDACs was first discovered in maize as an acidic nucleolar phospho- protein in a high-molecular-weight complex (Lusser et?al., 1997). The maize RPD3/HDA1-type HDAC, HDA101, is involved in sequence-specific modulation of histone modi- fications to regulate gene transcription and plant develop- ment (Rossi et?al., 2007). The rice HD2-type HDAC, HDT701, was found to be a histone H4 deacetylase that negatively regulates plant innate immunity by modulating histone H4 acetylation of defense-related genes (Ding et? al., 2012). Furthermore, down-regulation of rice HDT702 led to the production of narrowed leaves and stems (Hu et?al., 2009). In contrast, down-regulation of RPD3/HDA1-type HDACs by RNAi or amiRNA in rice led to various developmental defects. For examples, down-regulation of HDA703 by amiRNA reduced rice peduncle elongation and fertility, while inactivation of a closely related homolog HDA710 by RNAi affected vegetative growth (Hu et? al., 2009). Overexpression of OsHDAC1 leads to increased growth rate and altered plant architecture in rice (Jang et? al., 2003). Further analyses indicated that OsHDAC1 regu- lates the expression of OsNAC6 that controls seedling root growth in rice (Chung et?al., 2009). Taken together, these findings suggested that various HDACs play distinct roles in plant developmental processes. More recently, Arabidopsis HDACs were shown to interact with various transcription factors and chromatin remolding factors involved in repres- sion of gene expression in multiple development processes (Table?1 and Figure?1). TRANSCRIPTION REPRESSION IN PLANT DEVELOPMENT Histone acetylation and deacetylation play key roles in the regulation of flowering time in Arabidopsis (He et?al., 2003). Loss-of-function HDA6 mutants exhibit a late-flowering phe- notype, suggesting that HDA6 is involved in control of flow- ering time by histone deacetylation (Wu et?al., 2008). HDA6 directly interacts with the histone demethylase, FLOWERING