Biomedical subjects

Gorou Horiguchi

Publications and source records attributed to Gorou Horiguchi.

5 recordsLinked to original sources

PubMed2004

Transgene overexpression with cognate small interfering RNA in tobacco.

Small interfering RNAs (siRNAs) are a key component of RNA silencing, including cosuppression. Here, we show an example in which siRNA does not serve in the downregulation of target genes. A tobacco endoplasmic reticulum omega-3 fatty acid desaturase (NtFAD3) catalyzes the formation of alpha-linolenate (18:3). Introduction of the NtFAD3 gene into tobacco plants caused strong reduction of 18:3 content in leaf tissues, which is associated with the production of the NtFAD3 siRNAs. However, this silencing effect was lacking in the root tissues. Both the introduced NtFAD3 and endogenous NtFAD3 genes were expressed successfully, and the roots showed increased 18:3 phenotype. Surprisingly, the NtFAD3 siRNAs were produced even in the root tissues. Expression of a hairpin double-stranded RNA against the NtFAD3 gene caused efficient reduction of 18:3 content in root tissues. Therefore, cosuppression of the NtFAD3 gene in tobacco appears to include an as yet unidentified developmental stage and tissue-specific mechanism of regulation of siRNA function.

Fatty Acid Desaturases↗

PubMed2004

Overexpression of a novel small peptide ROTUNDIFOLIA4 decreases cell proliferation and alters leaf shape in Arabidopsis thaliana.

Leaf shape is determined by polar cell expansion and polar cell proliferation along the leaf axes. However, the genes controlling polar cell proliferation during leaf morphogenesis are largely unknown. We identified a dominant mutant of Arabidopsis thaliana, rotundifolia4-1D (rot4-1D), which possessed short leaves and floral organs. We showed that the altered leaf shape is caused by reduced cell proliferation, specifically in the longitudinal (proximal-distal) axis of the leaf, suggesting that the ROT4 gene controls polar cell proliferation in lateral organs. The ROT4 open-reading frame (ORF) encodes a novel small peptide that had not been identified in the Arabidopsis genome annotation. Overexpression of a ROT4-green fluorescence protein (GFP) fusion protein in transgenic plants recapitulated the rot4 phenotype, suggesting that ROT4 acts to restrict cell proliferation. The ROT4-GFP fusion protein localized to the plasma membrane when expressed in transgenic Arabidopsis plants. Phylogenetic analysis indicates that ROT4 defines a novel seed plant-specific family of small peptides with 22 members in Arabidopsis, ROT FOUR LIKE1-22 (RTFL1-22). All RTFL members share a conserved 29-amino acid domain, the RTF domain, and overexpression of the ROT4 RTF domain alone is sufficient to confer a rot4-1D phenotype. Loss-of-function mutations in several RTFL genes were aphenotypic, suggesting that there may be some functional redundancy between family members. Analyses by reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization revealed that ROT4 is expressed in the shoot apex and young leaves of wild-type plants, consistent with a role for ROT4 in controlling polarity-dependent cell proliferation during wild-type leaf morphogenesis.

Amino Acid Sequence↗

PubMed2004

RNA silencing in plants: a shortcut to functional analysis.

RNA silencing is a rapidly expanding research field, not only because it is a fundamental biological issue but also because its application in the control of gene expression is highly promising. Post-transcriptional gene silencing in plants is a form of RNA silencing by which target RNA is degraded in a sequence-specific manner. Findings regarding the central role that double-stranded RNA plays in triggering RNA silencing have prompted the development of many modified methods for RNA silencing. These methods, in combination with the development of genomic resources, have provided rapid and efficient means by which to investigate gene function in a wide range of plant species. This review addresses the technical aspects of RNA silencing in plants by introducing the principles of several methods of RNA silencing, as well as the advantages and disadvantages of each method.

Genetic Vectors↗

PubMed2003

Mutations in a gene for plastid ribosomal protein S6-like protein reveal a novel developmental process required for the correct organization of lateral root meristem in Arabidopsis.

Arabidopsis rfc3 mutants have previously been isolated with an altered fatty acid composition of membrane lipids. In this study, rfc3 was found to have a sucrose-conditional defect in the patterning of distal elements in the lateral root meristem. By utilizing this feature, a sucrose-sensitive process important for lateral root development was localized to the growing portion of rfc3 primary root. Because lateral root formation occurs at a later stage, this finding suggests the existence of an RFC3-dependent, non-primordium autonomous signal playing a role in the organization of lateral root meristem. Map-based cloning of RFC3 gene revealed that it encodes a plastid-localized ribosomal protein S6-like protein and provides a potential link between control of plastid gene expression and LR development.

Amino Acid Sequence↗

PubMed2002

Visualization by comprehensive microarray analysis of gene expression programs during transdifferentiation of mesophyll cells into xylem cells.

Plants have a unique transdifferentiation mechanism by which differentiated cells can initiate a new program of differentiation. We used a comprehensive analysis of gene expression in an in vitro zinnia (Zinnia elegans L.) culture model system to gather fundamental information about the gene regulation underlying the transdifferentiation of plant cells. In this model, photosynthetic mesophyll cells isolated from zinnia leaves transdifferentiate into xylem cells in a morphogenic process characterized by features such as secondary-wall formation and programmed cell death. More than 8,000 zinnia cDNA clones were isolated from an equalized cDNA library prepared from cultured cells transdifferentiating into xylem cells. Microarray analysis using these cDNAs revealed several types of unique gene regulation patterns, including: the transient expression of a set of genes during cell isolation, presumably induced by wounding; a rapid reduction in the expression of photosynthetic genes and the rapid induction of protein synthesis-associated genes during the first stage; the preferential induction of auxin-related genes during the subsequent stage; and the transient induction of genes closely associated with particular morphogenetic events, including cell-wall formation and degradation and programmed cell death during the final stage. This analysis also revealed a number of previously uncharacterized genes encoding proteins that function in signal transduction, such as protein kinases and transcription factors that are expressed in a stage-specific manner. These findings provide new clues to the molecular mechanisms of both plant transdifferentiation and wood formation.

Asteraceae↗