We have characterized a rice (Oryza sativa) dwarf mutant, dwarf11 (d11), that bears seeds of reduced length. To understand the mechanism by which seed length is regulated, the D11 gene was isolated by a map-based cloning method. The gene was found to encode a novel cytochrome P450 (CYP724B1), which showed homology to enzymes involved in brassinosteroid (BR) biosynthesis. The dwarf phenotype of d11 mutants was restored by the application of the brassinolide (BL). Compared with wild-type plants, the aberrant D11 mRNA accumulated at higher levels in d11 mutants and was dramatically reduced by treatment with BL, implying that the gene is feedback-regulated by BL. Precise determination of the defective step(s) in BR synthesis in d11 mutants proved intractable because of tissue specificity and the complex control of BR accumulation in plants. However, 6-deoxotyphasterol (6-DeoxoTY) and typhasterol (TY), but not any upstream intermediates before these compounds, effectively restored BR response in d11 mutants in a lamina joint bending assay. Multiple lines of evidence together suggest that the D11/CYP724B1 gene plays a role in BR synthesis and may be involved in the supply of 6-DeoxoTY and TY in the BR biosynthesis network in rice.

BackgroundThe intestine is one of the first affected organs in Parkinson’s disease (PD). PD subjects show abnormal staining for Escherichia coli and α-synuclein in the colon.MethodsWe recruited 52 PD patients and 36 healthy cohabitants. We measured serum markers and quantified the numbers of 19 fecal bacterial groups/genera/species by quantitative RT-PCR of 16S or 23S rRNA. Although the six most predominant bacterial groups/genera/species covered on average 71.3% of total intestinal bacteria, our analysis was not comprehensive compared to metagenome analysis or 16S rRNA amplicon sequencing.ResultsIn PD, the number of Lactobacillus was higher, while the sum of analyzed bacteria, Clostridium coccoides group, and Bacteroides fragilis group were lower than controls. Additionally, the sum of putative hydrogen-producing bacteria was lower in PD. A linear regression model to predict disease durations demonstrated that C. coccoides group and Lactobacillus gasseri subgroup had the largest negative and positive coefficients, respectively. As a linear regression model to predict stool frequencies showed that these bacteria were not associated with constipation, changes in these bacteria were unlikely to represent worsening of constipation in the course of progression of PD. In PD, the serum lipopolysaccharide (LPS)-binding protein levels were lower than controls, while the levels of serum diamine oxidase, a marker for intestinal mucosal integrity, remained unchanged in PD.ConclusionsThe permeability to LPS is likely to be increased without compromising the integrity of intestinal mucosa in PD. The increased intestinal permeability in PD may make the patients susceptible to intestinal dysbiosis. Conversely, intestinal dysbiosis may lead to the increased intestinal permeability. One or both of the two mechanisms may be operational in development and progression of PD.

Previously, we reported that the rice dwarf mutant, d1, is defective in the ␣ subunit of the heterotrimeric G protein (G␣). In the present study, gibberellin (GA) signaling in d1 and the role of the G␣ protein in the GA-signaling pathway were investigated. Compared with the wild type, GA induction of ␣-amylase activity in aleurone cells of d1 was greatly reduced. Relative to the wild type, the GA 3-treated aleurone layer of d1 had lower expression of Ramy1A, which encodes ␣-amylase, and OsGAMYB, which encodes a GAinducible transcriptional factor, and no increase in expression of Ca 2 ؉ -ATPase. However, in the presence of high GA concentrations, ␣-amylase induction occurred even in d1. The GA sensitivity of second leaf sheath elongation in d1 was similar to that of the wild type in terms of dose responsiveness, but the response of internode elongation to GA was much lower in d1. Furthermore, Os20ox expression was up-regulated, and the GA content was elevated in the stunted internodes of d1. All these results suggest that d1 affects a part of the GA-signaling pathway, namely the induction of ␣-amylase in the aleurone layer and internode elongation. In addition, a double mutant between d1 and another GA-signaling mutant, slr, revealed that SLR is epistatic to the D1, supporting that the G␣ protein is involved in GA signaling. However, the data also provide evidence for the presence of an alternative GA-signaling pathway that does not involve the G␣ protein. It is proposed that GA signaling via the G␣ protein may be more sensitive than that of the alternative pathway, as indicated by the low GA responsiveness of this G␣-independent pathway. H eterotrimeric G proteins are associated with the cytoplasmic face of the plasma membrane of eukaryotic cells and mediate signalings from receptors on the cell surface. The ␣-subunits of heterotrimeric G (G␣) proteins transduce signals from G protein-coupled receptors to effector proteins, accompanied by the GTPase-catalyzed hydrolysis of GTP. In mammals, a set of genes has been identified for each of the G protein subunits: more than 16 genes for the ␣ subunits, 5 genes for the ␤ subunit, and 6 genes for the ␥ subunit, most of which are expressed in a tissue-specific manner. Thus mammals contain multiforms of the G proteins that are probably involved in separate systems of signal transduction. Genomic and cDNA clones that encode polypeptides similar to the mammalian G␣ proteins have also been isolated from various plant species, including Arabidopsis (1), tomato (2), Lotus japonicas (3), rice (4), and soybean (5). However, with the exception of soybean, which has two genes, only a single gene has been identified in each plant species. Nevertheless, it has been proposed that the plant heterotrimeric G protein is involved in various signal transduction systems, including those of several plant hormones, blue and red light-mediated responses, pathogen resistance, and pathogen-related gene expression.By using a constitutive stimulator (Mas7) of GDP͞GTP exchange by G␣ proteins, Jon...

We used rice dwarf1 (d1) mutants lacking a single-copy G␣ gene and addressed G␣'s role in disease resistance. d1 mutants exhibited a highly reduced hypersensitive response to infection by an avirulent race of rice blast. Activation of PR gene expression in the leaves of the mutants infected with rice blast was delayed for 24 h relative to the wild type. H2O2 production and PR gene expression induced by sphingolipid elicitors (SE) were strongly suppressed in d1 cell cultures. Expression of the constitutively active OsRac1, a small GTPase Rac of rice, in d1 mutants restored SE-dependent defense signaling and resistance to rice blast. G␣ mRNA was induced by an avirulent race of rice blast and SE application on the leaf. These results indicated the role of G␣ in R gene-mediated disease resistance of rice. We have proposed a model for the defense signaling of rice in which the heterotrimeric G protein functions upstream of the small GTPase OsRac1 in the early steps of signaling. Heterotrimeric G proteins, a major group of signaling molecules involved in a variety of cellular activities in mammals, are mainly responsible for various cellular responses to external signals (1). In mammals, G proteins consist of ␣, ␤, and ␥ subunits, and at least 23 ␣, 6 ␤, and 12 ␥ genes are known (2). In plants, a number of pharmacological studies suggested that heterotrimeric G proteins are involved in a variety of signaling, including light reception (3), hormone signaling (4), and regulation of ion channels (5). However, direct evidence to support these observations has been obtained only recently (6). Analysis of mutations in a gene encoding the G␣ subunit of rice termed dwarf1 (d1) showed that G␣ is involved in stem elongation and the determination of seed shape in rice (7, 8) and influences gibberellin signal transduction (9). More recently, in Arabidopsis, mutants in the single-copy G␣ subunit gene were shown to have reduced cell division in aerial tissues (10) and to lack regulation of the ion channel by the phytohormone abscisic acid in guard cells (11). Furthermore, involvement of G␣ in phytochromemediated light signal transduction of Arabidopsis was also demonstrated by the study of transgenic plants overexpressing the G␣ gene (12). Arabidopsis mutants lacking G␤ were recently shown to have effects in leaf, flower, and fruit development (13). Therefore, the importance and diverse functions of heterotrimeric G proteins in the signaling of plants are recently becoming clear; however, the molecular mechanisms of G protein signaling remain to be studied.Many studies using inhibitors and agonists of heterotrimeric G proteins in several plant species have suggested that G proteins are involved in defense signaling (14-17). Particularly, changes in cytosolic Ca 2ϩ concentrations, which are often observed in elicitor-treated plant cells, are assumed to be regulated by heterotrimeric G proteins (18). However, the roles of the heterotrimeric G protein in plant defense have not been directly tested by the use of G protein mutants.In th...