Expression Profile and Cellular Localization of Maize Rpd3-Type Histone Deacetylases during Plant Development

Abstract

We analyzed the expression profile and cellular localization of the maize (Zea mays) Rpd3-type histone deacetylases genes ZmRpd3/101, ZmRpd3/102, and ZmRpd3/108 (indicated as ZmHDA101, ZmHDA102, and ZmHDA108 in the Plant Chromatin Database). This study shows that maize Rpd3 transcripts are present in all the organs and cellular domains analyzed, but we found that their amounts change during development, accumulating in the inner region of the endosperm, in vascular zones of the nucellus, in the tapetum, and in the tetrads. A similar expression profile and nucleus-cytoplasmic localization was observed for ZmRpd3 proteins. Glutathione S-transferase pull-down assays show that ZmRpd3 proteins can interact with the maize retinoblastoma-related (ZmRBR1) protein, an important regulator of cell cycle progression, and with the maize retinoblastoma-associated protein (ZmRbAp1). However, the three ZmRpd3 proteins do not mutually compete in the binding. These results suggest a general role of ZmRpd3 genes in the plant cell cycle and development. These observations also provide indications on possible mechanisms regulating their transcription and protein accumulation. Similarities in the gene expression profiles and protein interactions may indicate that functional redundancy among members of the ZmRpd3 gene family exists. However, a degree of functional divergence is also supported by our findings.Plant development is a striking example of a highly orchestrated biological process. Recent advances demonstrate that this intricate process is accomplished by diverse mechanisms and networks that operate at distinct levels within the nucleus (Goodrich and Tweedie, 2002). A fundamental mechanism controlling the selectivity of gene expression is the ability of many transcription factors to access the genome of eukaryotes (Struhl, 1999). This is achieved by packaging genes into chromatin, which impedes the binding of any proteins to their target DNA sequences. The accessibility of DNA to protein interaction is regulated by different enzymatic complexes that modulate nucleosomal structure. In the past few years, it has been shown that posttranslational modifications of histones, including acetylation, methylation, phosphorylation, and ubiquitination play a key role in modulating dynamic changes in chromatin structure and gene activity (Wu and Grunstein, 2000). Distinct histone modification patterns, together with direct modifications of the DNA, such as DNA methylation, are believed to form an epigenetic code acting as epigenetic marks or docking elements specifically read by regulatory factors that, in turn, can alter chromatin structure and regulate transcription (Strahl and Allis, 2000;Schreiber and Bernstein, 2002;Turner, 2002).Histone acetylation is the best-characterized type of histone modification (Cress and Seto, 2000;Roth et al., 2001). The enzymes responsible for maintaining the steady-state balance of histone acetylation are the histone acetyltransferases (HATs) and histone deacetylases (HDACs). Both enzymes are members o...

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