Abstract
Spatio-temporal regulation of gene expression during development depends on many factors. Mutations in Arabidopsis thaliana TEBICHI (TEB) gene encoding putative helicase and DNA polymerase domains-containing protein result in defects in meristem maintenance and correct organ formation, as well as constitutive DNA damage response and a defect in cell cycle progression; but the molecular link between these phenotypes of teb mutants is unknown. Here, we show that mutations in the DNA replication checkpoint pathway gene, ATR, but not in ATM gene, enhance developmental phenotypes of teb mutants, although atr suppresses cell cycle defect of teb mutants. Developmental phenotypes of teb mutants are also enhanced by mutations in RAD51D and XRCC2 gene, which are involved in homologous recombination. teb and teb atr double mutants exhibit defects in adaxial-abaxial polarity of leaves, which is caused in part by the upregulation of ETTIN (ETT)/AUXIN RESPONSIVE FACTOR 3 (ARF3) and ARF4 genes. The Helitron transposon in the upstream of ETT/ARF3 gene is likely to be involved in the upregulation of ETT/ARF3 in teb. Microarray analysis indicated that teb and teb atr causes preferential upregulation of genes nearby the Helitron transposons. Furthermore, interestingly, duplicated genes, especially tandemly arrayed homologous genes, are highly upregulated in teb or teb atr. We conclude that TEB is required for normal progression of DNA replication and for correct expression of genes during development. Interplay between these two functions and possible mechanism leading to altered expression of specific genes will be discussed.
Highlights
The determination of whether to change or maintain the expression status of groups of genes based on positional information of individual cells is central for the development of multicellular organisms
Our series of genetic analysis of tebichi mutant of model plant Arabidopsis thaliana suggest that TEB gene is involved in DNA replication and recombination
We show here that TEB gene is required for correct expression of many genes including genes regulating development. From these results we propose that TEB gene function is important for maintenance of gene expression pattern after DNA replication and recombination
Summary
The determination of whether to change or maintain the expression status of groups of genes based on positional information of individual cells is central for the development of multicellular organisms. Epigenetic regulation (such as methylation of cytosine in DNA or histone modification) is increasingly recognized as a normal, essential mechanism to control gene expression at the level of chromatin organization, and to regulate many aspects of development or responses to the environment [1,2,3,4]. Because the replication of the genome is regulated in part spatiotemporally, the S phase may offer an opportunity for cells to reprogram genome-wide epigenetic information, leading to a change in gene expression pattern [6,9]. DNA damages such as double-strand breaks (DSBs) have been shown to change the local histone modification pattern, which may change epigenetic information (reviewed in [5])
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