Biomedical subjects

Kenji Gomi

Publications and source records attributed to Kenji Gomi.

10 recordsLinked to original sources

PubMed2006

GAMYB controls different sets of genes and is differentially regulated by microRNA in aleurone cells and anthers.

GAMYB is a component of gibberellin (GA) signaling in cereal aleurone cells, and has an important role in flower development. However, it is unclear how GAMYB function is regulated. We examined the involvement of a microRNA, miR159, in the regulation of GAMYB expression in cereal aleurone cells and flower development. In aleurone cells, no miR159 expression was observed with or without GA treatment, suggesting that miR159 is not involved in the regulation of GAMYB and GAMYB-like genes in this tissue. miR159 was expressed in tissues other than aleurone, and miR159 over-expressors showed similar but more severe phenotypes than the gamyb mutant. GAMYB and GAMYB-like genes are co-expressed with miR159 in anthers, and the mRNA levels for GAMYB and GAMYB-like genes are negatively correlated with miR159 levels during anther development. Thus, OsGAMYB and OsGAMYB-like genes are regulated by miR159 in flowers. A microarray analysis revealed that OsGAMYB and its upstream regulator SLR1 are involved in the regulation of almost all GA-mediated gene expression in rice aleurone cells. Moreover, different sets of genes are regulated by GAMYB in aleurone cells and anthers. GAMYB binds directly to promoter regions of its target genes in anthers as well as aleurone cells. Based on these observations, we suggest that the regulation of GAMYB expression and GAMYB function are different in aleurone cells and flowers in rice.

Amino Acid Sequence↗

PubMed2006

Characterization of cDNAs encoding two distinct miraculin-like proteins and stress-related modulation of the corresponding mRNAs in Citrus jambhiri lush.

Two distinct full-length cDNAs from rough lemon that encoded miraculin-like proteins were isolated by random amplification of cDNA ends (RACEs), based on sequence information from subtractive PCR previously described, and designated as RlemMLP1 and RlemMLP2. The transcripts of both RlemMLP1 and RlemMLP2 were not detected in leaves, or stems but accumulated in fruits. Transcripts accumulated to higher levels in leaves after wounding, inoculation with conidia of Alternaria alternata, or treatment with methyl jasmonate vapors. Treatment with methyl salicylate antagonized the signaling pathway of wounding. Treatment with methyl salicylate at 2 h after wounding significantly reduced wounding-induced gene expression of both RlemMLP1 and RlemMLP2. Protein products of these genes were obtained by using a prokaryotic expression system, and had protease inhibitor activity. RlemMLP2, but not RlemMLP1, contained a thaumatin motif, and only RlemMLP2 showed anti-fungal activity against Alternaria citri. Cellular localization analysis with RlemMLP1 or RlemMLP2 fused to a green fluorescence protein gene following transient translation using a particle bombardment in onion cells indicated that both RlemMLP1 and RlemMLP2 were localized to the cytosol. These evidences revealed that rough lemon RlemMLPs are likely to have defensive function against pathogens at least when host cells are broken by their infections.

Acetates↗

PubMed2006

Production and characterization of auxin-insensitive rice by overexpression of a mutagenized rice IAA protein.

Since auxin was first isolated and characterized as a plant hormone, the underlying molecular mechanism of auxin signaling has been elucidated primarily in dicot plants represented by Arabidopsis. In monocot plants, the molecular mechanism of auxin signaling has remained unclear, despite various physiological experiments. To understand the function and mechanism of auxin signaling in rice (Oryza sativa), we focused on the IAA gene, a well-studied gene in Arabidopsis that serves as a negative regulator of auxin signaling. We found 24 IAA gene family members in the rice genome. OsIAA3 is one of these family members whose expression is rapidly increased in response to auxin. We produced transgenic rice harboring mOsIAA3-GR, which can overproduce mutant OsIAA3 protein containing an amino acid change in domain II to cause a gain-of-function phenotype, by treatment with dexamethasone. The transgenic rice was insensitive to auxin and gravitropic stimuli, and exhibited short leaf blades, reduced crown root formation, and abnormal leaf formation. These results suggest that, in rice, auxin is important for development and its signaling is mediated by IAA genes.

Amidohydrolases↗

PubMed2005

A mitogen-activated protein kinase NtMPK4 activated by SIPKK is required for jasmonic acid signaling and involved in ozone tolerance via stomatal movement in tobacco.

The mitogen-activated protein kinase (MAPK) cascade is involved in responses to biotic and abiotic stress in plants. In this study, we isolated a new MAPK, NtMPK4, which is a tobacco homolog of Arabidopsis MPK4 (AtMPK4). NtMPK4 was activated by wounding along with two other wound-responsive tobacco MAPKs, WIPK and SIPK. We found that NtMPK4 was activated by salicylic acid-induced protein kinase kinase (SIPKK), which has been isolated as an SIPK-interacting MAPK kinase. In NtMPK4 activity-suppressed tobacco, wound-induced expression of jasmonic acid (JA)-responsive genes was inhibited. NtMPK4-silenced plants showed enhanced sensitivity to ozone. Inversely, transgenic tobacco plants, in which SIPKK or the constitutively active type SIPKK(EE) was overexpressed, exhibited greater responsiveness to wounding with enhanced resistance to ozone. We further found that NtMPK4 was expressed preferentially in epidermis, and the enhanced sensitivity to ozone in NtMPK4-silenced plants was caused by an abnormal regulation of stomatal closure in an ABA-independent manner. These results suggest that NtMPK4 is involved in JA signaling and in stomatal movement.

Cyclopentanes↗

PubMed2005

Crown rootless1, which is essential for crown root formation in rice, is a target of an AUXIN RESPONSE FACTOR in auxin signaling.

Although the importance of auxin in root development is well known, the molecular mechanisms involved are still unknown. We characterized a rice (Oryza sativa) mutant defective in crown root formation, crown rootless1 (crl1). The crl1 mutant showed additional auxin-related abnormal phenotypic traits in the roots, such as decreased lateral root number, auxin insensitivity in lateral root formation, and impaired root gravitropism, whereas no abnormal phenotypic traits were observed in aboveground organs. Expression of Crl1, which encodes a member of the plant-specific ASYMMETRIC LEAVES2/LATERAL ORGAN BOUNDARIES protein family, was localized in tissues where crown and lateral roots are initiated and overlapped with beta-glucuronidase staining controlled by the DR5 promoter. Exogenous auxin treatment induced Crl1 expression without de novo protein biosynthesis, and this induction required the degradation of AUXIN/INDOLE-3-ACETIC ACID proteins. Crl1 contains two putative auxin response elements (AuxREs) in its promoter region. The proximal AuxRE specifically interacted with a rice AUXIN RESPONSE FACTOR (ARF) and acted as a cis-motif for Crl1 expression. We conclude that Crl1 encodes a positive regulator for crown and lateral root formation and that its expression is directly regulated by an ARF in the auxin signaling pathway.

Amino Acid Motifs↗

PubMed2004

GID2, an F-box subunit of the SCF E3 complex, specifically interacts with phosphorylated SLR1 protein and regulates the gibberellin-dependent degradation of SLR1 in rice.

The phytohormone gibberellin (GA) controls growth and development in plants. Previously, we identified a rice F-box protein, gibberellin-insensitive dwarf2 (GID2), which is essential for GA-mediated DELLA protein degradation. In this study, we analyzed the biological and molecular biological properties of GID2. Expression of GID2 preferentially occurred in rice organs actively synthesizing GA. Domain analysis of GID2 revealed that the C-terminal regions were essential for the GID2 function, but not the N-terminal region. Yeast two-hybrid assay and immunoprecipitation experiments demonstrated that GID2 is a component of the SCF complex through an interaction with a rice ASK1 homolog, OsSkp15. Furthermore, an in vitro pull-down assay revealed that GID2 specifically interacted with the phosphorylated Slender Rice 1 (SLR1). Taken these results together, we conclude that the phosphorylated SLR1 is caught by the SCFGID2 complex through an interacting affinity between GID2 and phosphorylated SLR1, triggering the ubiquitin-mediated degradation of SLR1.

Cullin Proteins↗

PubMed2003

Accumulation of phosphorylated repressor for gibberellin signaling in an F-box mutant.

Gibberellin (GA) regulates growth and development in plants. We isolated and characterized a rice GA-insensitive dwarf mutant, gid2. The GID2 gene encodes a putative F-box protein, which interacted with the rice Skp1 homolog in a yeast two-hybrid assay. In gid2, a repressor for GA signaling, SLR1, was highly accumulated in a phosphorylated form and GA increased its concentration, whereas SLR1 was rapidly degraded by GA through ubiquitination in the wild type. We conclude that GID2 is a positive regulator of GA signaling and that regulated degradation of SLR1 is initiated through GA-dependent phosphorylation and finalized by an SCF(GID2)-proteasome pathway.

Alleles↗

PubMed2003

Gibberellin signalling pathway.

Recent molecular biological and genetical studies have identified several positive and negative regulators of gibberellin (GA) signalling pathways in higher plants. The DELLA protein functions as a negative regulator of GA signalling; its degradation through the ubiquitin/proteasome pathway is a key event in the regulation of GA-stimulated processes.

Gene Expression Regulation, Developmental↗

PubMed2003

Epoxide hydrolase: a mRNA induced by the fungal pathogen Alternaria alternata on rough lemon (Citrus jambhiri Lush).

An expression profile of genes induced by non-pathogenic Alternaria alternata on rough lemon leaves was obtained by sequencing 500 subtractive PCR clones generated from mRNA of leaves inoculated with the fungus after subtraction with that of non-inoculated leaves. About 6% of the cDNA sequences had homology to known putative defense-related genes including epoxide hydrolase. A full-length cDNA (951 bp) from rough lemon that encoded epoxy hydrolase was isolated by random amplification of cDNA ends (RACEs), based on sequence information from subtractive PCR, and designated as RlemEH. The product of this gene expressed with an in vitro translation system with Escherichia coli also had activity of a soluble type of epoxide hydrolase. The transcript of rough lemon RlemEH was not detected in flowers, fruits, stems or leaves, but was induced after inoculation of leaves with conidia of Alternaria alternata, wounding, or treatment with C6 volatiles, including trans-2-hexenol and cis-3-hexenol, and methyl jasmonate. The response of the epoxide hydrolase gene correlated well with the activation of defense mechanisms induced in plant-fungus interactions.

Aldehydes↗

PubMed2003

Characterization of a hydroperoxide lyase gene and effect of C6-volatiles on expression of genes of the oxylipin metabolism in Citrus.

A number of C6-volatile products of the lipoxygenase (LOX) pathway was examined for their antifungal activity and a potential role as a signal molecule in citrus. trans-2-Hexenal induced the rough lemon lipoxygenase gene (RlemLOX), hydroperoxide lyase gene (RlemHPL) and AOS gene, but hexanal, and hexanol suppressed them. cis-3-Hexenol and trans-2-hexenol increased expression of the AOS gene but not RlemLOX and RlemHPL. Transcripts of the RlemHPL and AOS gene were detected constitutively in leaves by northern blot, but wounding or inoculation with nonpathogenic Alternaria alternata rapidly increased the transcript accumulation. Transcripts of the RlemHPL and AOS genes were also induced with pathogenic A. alternata, which produces the host-selective ACR-toxin, but the signal declined rapidly after inoculation. An increase in enzymatic activity of HPL after wounding or inoculation with nonpathogen was suppressed in leaves infected with the pathogen. Interestingly, vapor treatment with trans-2-hexenol delayed necrotic spot formation in the leaves inoculated with the pathogenic A. alternata. Since trans-2-hexenol has no antifungal activity to A. alternata and also did not inhibit necrosis formation by ACR-toxin alone, the delay of symptoms may be caused by activation of AOS in the LOX pathway to produce oxylipin derivatives such as methyl jasmonate for activation of defense related genes with antifungal activity.

Aldehyde-Lyases↗