Biomedical subjects

M Ohgishi

Publications and source records attributed to M Ohgishi.

4 recordsLinked to original sources

PubMed2001

Negative autoregulation of the Arabidopsis homeobox gene ATHB-2.

The Arabidopsis homeobox gene ATHB-2 is tightly regulated by light signals, and is thought to direct morphological changes during shade avoidance responses. To understand how ATHB-2 mediates light signals in plant morphogenesis, we investigated its transcriptional network. We constructed a gene encoding a chimeric transcription factor (HD-Zip-2-V-G) that is expected to activate target genes of ATHB-2 in a glucocorticoid-dependent manner. In transgenic Arabidopsis plants expressing HD-Zip-2-V-G, glucocorticoid treatment activates the ATHB-2 gene itself, independent of de novo protein synthesis. An in vitro DNase I-footprinting experiment showed that recombinant ATHB-2 protein specifically bound to an ATHB-2 promoter region. These complementary results indicate that ATHB-2 recognizes its own promoter. Consistent with the fact that ATHB-2 itself has been shown to act as a repressor, expression of the endogenous ATHB-2 gene was repressed in transgenic plants overexpressing an ATHB-2 transgene. Moreover, target-gene analysis using the HD-Zip-2-V-G suggested that ATHB-2 recognizes other HD-Zip II subfamily genes. We conclude that ATHB-2 has a negative autoregulatory loop and may be involved in a complicated transcriptional network involving paralogous genes, as is the case with animal homeobox genes.

Arabidopsis↗

PubMed1999

Shade avoidance responses are mediated by the ATHB-2 HD-zip protein, a negative regulator of gene expression.

The ATHB-2 gene encoding an homeodomain-leucine zipper protein is rapidly and strongly induced by changes in the ratio of red to far-red light which naturally occur during the daytime under the canopy and induce in many plants the shade avoidance response. Here, we show that elevated ATHB-2 levels inhibit cotyledon expansion by restricting cell elongation in the cotyledon-length and -width direction. We also show that elevated ATHB-2 levels enhance longitudinal cell expansion in the hypocotyl. Interestingly, we found that ATHB-2-induced, as well as shade-induced, elongation of the hypocotyl is dependent on the auxin transport system. In the root and hypocotyl, elevated ATHB-2 levels also inhibit specific cell proliferation such as secondary growth of the vascular system and lateral root formation. Consistent with the key role of auxin in these processes, we found that auxin is able to rescue the ATHB-2 lateral root phenotype. We also show that reduced levels of ATHB-2 result in reciprocal phenotypes. Moreover, we demonstrate that ATHB-2 functions as a negative regulator of gene expression in a transient assay. Remarkably, the expression in transgenic plants of a derivative of ATHB-2 with the same DNA binding specificity but opposite regulatory properties results in a shift in the orientation of hypocotyl cell expansion toward radial expansion, and in an increase in hypocotyl secondary cell proliferation. A model of ATHB-2 function in the regulation of shade-induced growth responses is proposed.

Arabidopsis↗

PubMed1984

Experimental study of aggression and catharsis in Japanese.

28 Japanese subjects were tested to investigate how aggressive motive and TAT fantasy writing would influence provoked subjects. To examine this psychologically and physiologically subjects' changes in affect and respiration rate were measured. The results showed significant provocation and cathartic effects.

Abreaction↗

PubMed1978

[Hemispheric differences in the mode of information processing (author's transl)].

To examine hemispheric differences in the mode of information processing, 24 normal right-handed subjects were required to make same or different responses to a set of letters varying in number from two to four which were all identical or contained one letter differing from the rest. When letters were presented in the normal upright position, the left hemisphere showed serial processing wherein reaction times increased as a function of number of letters. The right hemisphere, however, showed no increase of reaction times, i.e. parallel processing. When letters were presented in the inverted upside-down position, the left hemisphere showed partial serial processing, despite letters being analyzed physically. The results suggest that visuopatial analysis doesn't always force parallel processing in the left hemisphere.

Adult↗