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<jats:title>Abstract</jats:title><jats:p>Most eukaryotic organisms employ a telomerase complex for the maintenance of chromosome ends. The core of this complex is composed of telomerase reverse transcriptase (TERT) and telomerase RNA (TR) subunits. The TERT reverse transcriptase (RT) domain synthesises telomeric DNA using the TR template sequence. The other TERT domains contribute to this process in different ways. In particular, the TERT RNA-binding domain (TRBD) interacts with specific TR motif(s). Using a yeast 3-hybrid system, we show the critical role of <jats:italic>Arabidopsis thaliana</jats:italic> (At) TRBD and embryophyta-conserved KRxR motif in the unstructured linker preceding the TRBD domain for binding to the recently identified AtTR subunit. We also show the essential role of the predicted P4 stem and pseudoknot AtTR structures and provide evidence for the binding of AtTRBD to pseudoknot and KRxR motif stabilising interaction with the P4 stem structure. Our results thus provide the first insight into the core part of the plant telomerase complex.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Sugars, synthesized by photosynthesis in source organs, are loaded and utilized as an energy source and carbon skeleton in sink organs, and also known to be important signal molecules regulating gene expression in higher plants. The expression of genes coding for <jats:italic>sporamin</jats:italic> and <jats:italic>β-amylase</jats:italic>, the two most abundant proteins in storage roots of sweet potato, is coordinately induced by sugars. We previously reported on the identification of the carbohydrate metabolic signal-responsible element-1 (CMSRE-1) essential for the sugar-responsible expression of two genes. However, transcription factors that bind to this sequence have not been identified. In this study, we performed yeast one-hybrid screening using the sugar-responsible minimal promoter region of the ß-amylase gene as bait and a library composed only transcription factor cDNAs of <jats:italic>Arabidopsis</jats:italic>. Two clones, named <jats:underline>A</jats:underline>ctivator protein binding to <jats:underline>C</jats:underline>MS<jats:underline>RE</jats:underline>-1 (ACRE), encoding AP2/ERF transcription factors were isolated. ACRE showed transactivation activity of the sugar-responsible minimal promoter in a CMSRE-1-dependent manner in <jats:italic>Arabidopsis</jats:italic> protoplasts. Electric mobility shift assay (EMSA) using recombinant proteins and transient co-expression assay in <jats:italic>Arabidopsis</jats:italic> protoplasts revealed that ACRE could actually act to the CMSRE-1. Among the DEHYDRATION -RESPONSIVE ELEMENT BINDING FACTOR (DREB) subfamily, almost all homologs including ACRE, could act on the DRE, while only three ACREs could act to the CMSRE-1. Moreover, ACRE-homologs of Japanese morning glory also have the same property of DNA-binding preference and transactivation activity through the CMSRE-1. These findings suggested that ACRE plays an important role in the mechanism regulating the sugar-responsible gene expression through the CMSRE-1 conserved across plant species.</jats:p>