Cardiac Presynaptic Sympathetic Nervous Function Evaluated by Cardiac PET in Patients with Chronotropic Incompetence Without Heart Failure.

Chronotropic incompetence (CTI), the inability of the heart to increase its rate with increased activity, leads to exercise intolerance and predicts overall mortality. We previously reported that cardiac β-adrenergic receptor downregulation occurs in patients with CTI without heart failure (HF), indicating postsynaptic sympathetic nervous dysfunction. However, cardiac presynaptic sympathetic nervous system function in CTI is not fully understood.

CRES-T, an effective gene silencing system utilizing chimeric repressors.

Chimeric REpressor gene Silencing Technology (CRES-T) is a useful tool for functional analysis of plant transcription factors. In this system, a chimeric repressor that is produced by fusion of a transcription factor to the plant-specific EAR-motif repression domain (SRDX) suppresses target genes of a transcription factor dominantly over the activity of endogenous and functionally redundant transcription factors. As a result, the transgenic plants that express a chimeric repressor exhibit phenotypes similar to loss-of-function of the alleles of the gene encoding the transcription factor.

Generation of chimeric repressors that confer salt tolerance in Arabidopsis and rice.

We show here that transgenic Arabidopsis plants that expressed chimeric repressors derived from the AtMYB102, ANAC047, HRS1, ZAT6 and AtERF5 transcription factors were tolerant to treatment with 400 mm NaCl, which was lethal to wild-type plants. The transgenic plants grew well, without any apparent differences from the wild-type plants under normal growth condition. The transgenic lines expressing the AtMYB102, ANAC047 and HRS1 chimeric repressors germinated in the presence of 225 mm NaCl, while those expressing the ZAT6 and AtERF5 did not.

AtMYBL2, a protein with a single MYB domain, acts as a negative regulator of anthocyanin biosynthesis in Arabidopsis.

In Arabidopsis, MYB transcription factors regulate flavonoid biosynthesis via the formation of protein complexes with a basic helix-loop-helix (bHLH) transcription factor and a WD40 repeat protein. Several R3-type single-MYB proteins (R3-MYB), such as CPC and TRY, act as negative regulators of the development of epidermal cells. However, such regulators of flavonoid biosynthesis have not yet been reported, to our knowledge.

Suppression of the biosynthesis of proanthocyanidin in Arabidopsis by a chimeric PAP1 repressor.

Flavonoids are secondary metabolites that are specific to higher plants. PAP1, a member of the family of MYB domain transcription factors in Arabidopsis, is a positive regulator of the biosynthesis of anthocyanin. We show here that a chimeric PAP1 repressor, in which the EAR-motif repression domain from SUPERMAN was fused to PAP1, suppressed the expression of four flavonoid biosynthetic genes, namely CHS, DFR, LDOX, and BAN, in siliques, and inhibited the accumulation of proanthocyanidin, even in the presence of an endogenous positive regulator, such as TT2.

Complete maturation of the plastid protein translocation channel requires a type I signal peptidase.

The protein translocation channel at the plastid outer envelope membrane, Toc75, is essential for the viability of plants from the embryonic stage. It is encoded in the nucleus and is synthesized with a bipartite transit peptide that is cleaved during maturation. Despite its important function, the molecular mechanism and the biological significance of the full maturation of Toc75 remain unclear.

Tobacco ZFT1, a transcriptional repressor with a Cys2/His2 type zinc finger motif that functions in spermine-signaling pathway.

We previously proposed that a spermine (Spm)-mediated signal transduction pathway is involved in the hypersensitive response induced by Tobacco mosaic virus (TMV) in tobacco plants. To identify regulatory component(s) of this pathway, we surveyed a tobacco cDNA library and found that the ZFT1 gene, which encodes a Cys2/His2 type zinc-finger protein, is Spm-responsive. ZFT1 was not induced by two other polyamines, putrescine and spermidine, or by salicylic acid (SA), jasmonic acid or ethylene.

A chimeric AtMYB23 repressor induces hairy roots, elongation of leaves and stems, and inhibition of the deposition of mucilage on seed coats in Arabidopsis.

We reported previously that a chimeric repressor, in which a transcription factor was fused to the EAR motif repression domain, acted as a dominant repressor and suppressed the expression of target genes, such that resultant phenotypes were similar to those associated with loss-of-function alleles. We report here that expression of the chimeric AtMYB23 repressor induced a variety of morphological changes, namely the ectopic formation of root hairs, a short primary root, elongation of leaves and of inflorescence stems, and absence of the accumulation of mucilage on seed coats, in addition to disruption of the development of trichomes. The short primary root and the elongation of leaves and stems appeared to be due to the reduced and enhanced lengthwise expansion, respectively, of epidermal cells.

Identification of the minimal repression domain of SUPERMAN shows that the DLELRL hexapeptide is both necessary and sufficient for repression of transcription in Arabidopsis.

We reported previously that the carboxy-terminal 30 amino acids of SUPERMAN (SUPRD) function as a repression domain in Arabidopsis. In this study, we identified the peptide sequences in SUPRD that is both necessary and sufficient for repression of transcription. To our surprise, the hexapeptide DLELRL was sufficient, by itself, to confer the ability to repress transcription on a DNA-binding domain.

Stress-responsive zinc finger gene ZPT2-3 plays a role in drought tolerance in petunia.

The petunia gene, ZPT2-3, encodes a Cys2/His2-type zinc finger protein. Here, we describe the expression of ZPT2-3 in response to various stresses and the effects of ZPT2-3 overexpression in transgenic petunia. Mechanical wounding induced accumulation of ZPT2-3 transcript, and the activity of ZPT2-3::luciferase was conferred by the 1668-bp ZPT2-3 upstream sequence, both locally and systemically.

Dominant repression of target genes by chimeric repressors that include the EAR motif, a repression domain, in Arabidopsis.

The redundancy of genes for plant transcription factors often interferes with efforts to identify the biologic functions of such factors. We show here that four different transcription factors fused to the EAR motif, a repression domain of only 12 amino acids, act as dominant repressors in transgenic Arabidopsis and suppress the expression of specific target genes, even in the presence of the redundant transcription factors, with resultant dominant loss-of-function phenotypes. Chimeric EIN3, CUC1, PAP1, and AtMYB23 repressors that included the EAR motif dominantly suppressed the expression of their target genes and caused insensitivity to ethylene, cup-shaped cotyledons, reduction in the accumulation of anthocyanin, and absence of trichomes, respectively.

The SUPERMAN protein is an active repressor whose carboxy-terminal repression domain is required for the development of normal flowers.

SUPERMAN was identified as a putative regulator of transcription that acts in floral development, but its function remains to be clarified. We demonstrate here that SUPERMAN is an active repressor whose repression domain is located in the carboxy-terminal region. Ectopic expression of SUPERMAN that lacked the repression domain resulted in a phenotype similar to that of superman mutants, demonstrating that the repression activity of SUPERMAN is essential for the development of normal flowers.