Abstract
Hybrids between different inbred varieties display novel patterns of gene expression resulted from parental variation in allelic nucleotide sequences. To study the function of chromatin regulators in hybrid gene expression, the histone deacetylase gene OsHDT1 whose expression displayed a circadian rhythm was over-expressed or inactivated by RNAi in an elite rice parent. Increased OsHDT1 expression did not affect plant growth in the parent but led to early flowering in the hybrid. Nonadditive up-regulation of key flowering time genes was found to be related to flowering time of the hybrid. Over-expression of OsHDT1 repressed the nonadditive expression of the key flowering repressors in the hybrid (i.e. OsGI and Hd1) inducing early flowering. Analysis of histone acetylation suggested that OsHDT1 over-expression might promote deacetylation on OsGI and Hd1 chromatin during the peak expression phase. High throughput differential gene expression analysis revealed that altered OsHDT1 levels affected nonadditive expression of many genes in the hybrid. These data demonstrate that nonadditive gene expression was involved in flowering time control in the hybrid rice and that OsHDT1 level was important for nonadditive or differential expression of many genes including the flowering time genes, suggesting that OsHDT1 may be involved in epigenetic control of parental genome interaction for differential gene expression.
Highlights
Epigenetic programming is suggested to be key mechanisms in the interaction between different genomes in hybrids [1]
We show that the expression of OsHDT1 displayed a circadian rhythm and that increased OsHDT1 could suppress overdominance expression of flowering time repressors in the hybrid leading to early flowering under long day condition, providing evidence of overdominance gene action in heterosis
OsHDT1 expression displays a circadian rhythm Recent results have shown that differential epigenetic modifications correlated with changes in transcript levels among hybrids and parental lines [6]
Summary
Epigenetic programming is suggested to be key mechanisms in the interaction between different genomes in hybrids [1]. Inbred parental genome interaction in hybrids leads to differential expression patterns that could be equal to the mid-parent (additivity), higher or lower than the mid-parent (nonadditivity), above the high-parent or below the low-parent (over- or underdominance) [2]. Novel patterns of gene expression or action in hybrids may result from parental variation in allelic nucleotide sequence and transcript abundance, which is supposed to be an important genetic component of phenotypic diversity [3,4]. It is likely that multiple mechanisms including epigenetic processes are involved in parental genome interaction leading to distinct expression patterns in the hybrid, which are presently not understood
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