The histone deacetylase OsHDAC1 epigenetically regulates the <i>OsNAC6</i> gene that controls seedling root growth in rice

다국어 초록 (Multilingual Abstract)

<P>Summary</P><P>We have previously isolated a rice gene encoding a histone deacetylase, <I>OsHDAC1</I>, and observed that its transgenic overexpression increases seedling root growth. To identify the transcriptional repression events that occur as a result of <I>OsHDAC1</I> overexpression (<I>OsHDAC1</I><SUP><I>OE</I></SUP>), a global profiling of root-expressed genes was performed on <I>OsHDAC1</I><SUP><I>OE</I></SUP> or HDAC inhibitor-treated non-transgenic (NT) roots, in comparison with untreated NT roots. We selected 39 genes that are induced and repressed in HDAC inhibitor-treated NT and <I>OsHDAC1</I><SUP><I>OE</I></SUP> roots, compared with NT roots, respectively. Interestingly, <I>OsNAC6</I>, a member of the NAM-ATAF-CUC (NAC) family, was identified as a key component of the OsHDAC1 regulon, and was found to be epigenetically repressed by OsHDAC1 overexpression. The root phenotype of <I>OsNAC6</I> knock-out seedlings was observed to be similar to that of the <I>OsHDAC1</I><SUP><I>OE</I></SUP> seedlings. Conversely, the root phenotype of the <I>OsNAC6</I> overexpressors was similar to that of the <I>OsHDAC1</I> knock-out seedlings. These observations indicate that OsHDAC1 negatively regulates the <I>OsNAC6</I> gene that primarily mediates the alteration in the root growth of the <I>OsHDAC1</I><SUP><I>OE</I></SUP> seedlings. Chromatin immunoprecipitation assays of the <I>OsNAC6</I> promoter region using antibodies specific to acetylated histones H3 and H4 revealed that OsHDAC1 epigenetically represses the expression of <I>OsNAC6</I> by deacetylating K9, K14 and K18 on H3 and K5, K12 and K16 on H4.</P>