A collection of inducible transcription factor-glucocorticoid receptor fusion lines for functional analyses in Arabidopsis thaliana

Arabidopsis possesses approximately 2000 transcription factors (TFs) in its genome. They play pivotal roles in various biological processes but analysis of their function has been hampered by the overlapping nature of their activities. To uncover clues to their function, we generated inducible TF lines using glucocorticoid receptor (GR) fusion techniques in Arabidopsis. These TF-GR lines each express one of 1255 TFs as a fusion with the GR gene. An average 14 lines of T₂ transgenic TF-GR lines were generated for each TF to monitor their function. To evaluate these transcription lines, we induced the TF-GR lines of phytochrome-interacting factor 4, which controls photomorphogenesis, with synthetic glucocorticoid dexamethasone. These phytochrome-interacting factor 4-GR lines showed the phenotype described in a previous report. We performed screening of the other TF-GR lines for TFs involved in light signaling under blue and far-red light conditions and identified 13 novel TF candidates. Among these, we found two lines showing higher anthocyanin accumulation under light conditions and we examined the regulating genes. These results indicate that the TF-GR lines can be used to dissect functionally redundant genes in plants and demonstrate that the TF-GR line collection can be used as an effective tool for functional analysis of TFs.

Physiological function of photoreceptor UVR8 in UV-B tolerance in the liverwort Marchantia polymorpha

The physiological importance of MpUVR8 in UV-B resistance and translocation in a UV-B-dependent manner from the cytosol into the nucleus is characterized in Marchantia polymorpha. UV RESISTANCE LOCUS 8 (UVR8) is an ultraviolet-B (UV-B) light receptor functioning for UV-B sensing and tolerance in Arabidopsis thaliana and other species. It is unclear whether UVR8 physiologically functions in UV-B-induced defense responses in Marchantia polymorpha, which belongs to the earliest diverging group of embryophyte lineages. Here, we demonstrate that UVR8 has a physiological function in UV-B tolerance and that there is a UVR8-dependent pathway involved. In addition, a UVR8-independent pathway is revealed. We examine the tissue-specific expression pattern of M. polymorpha UVR8 (MpUVR8), showing that it is highly expressed in the apical notch in thalli and gametangiophores, as well as in antheridial and archegonial heads. Furthermore, Mpuvr8^KO plant transformants, in which the MpUVR8 locus was disrupted, were produced and analyzed to understand the physiological and molecular function of MpUVR8. Analysis using these plants indicates the important roles of MpUVR8 and MpUVR8-regulated genes, and of MpUVR8-independent pathways in UV-B tolerance. Subcellular localization of Citrine-fused MpUVR8 in M. polymorpha cells was also investigated. It was found to translocate from the cytosol into the nucleus in response to UV-B irradiation. Our findings indicate strong conservation of the physiological function of UVR8 and the molecular mechanisms for UVR8-dependent signal transduction through regulation of gene expression in embryophytes.

Biosynthesis of riccionidins and marchantins is regulated by R2R3-MYB transcription factors in Marchantia polymorpha

R2R3-MYB transcription factors constitute the largest gene family among plant transcription factor families. They became largely divergent during the evolution of land plants and regulate various biological processes. The functions of R2R3-MYBs are mostly characterized in seed plants but are poorly understood in non-seed plants. Here, we examined the function of two R2R3-MYB genes of Marchantia polymorpha (Mapoly0073s0038 and Mapoly0006s0226) that are closely related to subgroup 4 of the R2R3-MYB family. We performed LC/MS/MS metabolomics, RNA-seq analysis and expression analysis in overexpressors and knockout mutants of MpMYB14 and MpMYB02. Overexpression of MpMYB14 remarkably increased the amount of riccionidins, which are specific anthocyanins in liverworts and a few flowering plants. In contrast, overexpression of MpMYB02 increased the amount of several marchantins, which are characteristic cyclic bis (bibenzyl ether) compounds in M. polymorpha and related liverworts. Knockouts of MpMYB14 and MpMYB02 abolished the accumulation of riccionidins and marchantins, respectively. The expression of MpMYB14 was up-regulated by UV-B irradiation, N deficiency, and NaCl treatment, whereas the expression of MpMYB02 was down-regulated by NaCl treatment. Our results suggest that the regulatory framework of phenolic metabolism by R2R3-MYB was already established in early land plants.

Repression of Nitrogen Starvation Responses by Members of the Arabidopsis GARP-Type Transcription Factor NIGT1/HRS1 Subfamily

Nitrogen (N) is often a limiting nutrient whose availability determines plant growth and productivity. Because its availability is often low and/or not uniform over time and space in nature, plants respond to variations in N availability by altering uptake and recycling mechanisms, but the molecular mechanisms underlying how these responses are regulated are poorly understood. Here, we show that a group of GARP G2-like transcription factors, Arabidopsis thaliana NITRATE-INDUCIBLE, GARP-TYPE TRANSCRIPTIONAL REPRESSOR1/HYPERSENSITIVE TO LOW Pi-ELICITED PRIMARY ROOT SHORTENING1 proteins (NIGT1/HRS1s), are factors that bind to the promoter of the N starvation marker NRT2.4 and repress an array of N starvation-responsive genes under conditions of high N availability. Transient assays and expression analysis demonstrated that NIGT1/HRS1s are transcriptional repressors whose expression is regulated by N availability. We identified target genes of the NIGT1/HRS1s by genome-wide transcriptome analyses and found that they are significantly enriched in N starvation response-related genes, including N acquisition, recycling, remobilization, and signaling genes. Loss of NIGT1/HRS1s resulted in deregulation of N acquisition and accumulation. We propose that NIGT1/HRS1s are major regulators of N starvation responses that play an important role in optimizing N acquisition and utilization under fluctuating N conditions.

Genetic Nature of Elemental Contents in Wheat Grains and Its Genomic Prediction: Toward the Effective Use of Wheat Landraces from Afghanistan

Profiling elemental contents in wheat grains and clarifying the underlying genetic systems are important for the breeding of biofortified crops. Our objective was to evaluate the genetic potential of 269 Afghan wheat landraces for increasing elemental contents in wheat cultivars. The contents of three major (Mg, K, and P) and three minor (Mn, Fe, and Zn) elements in wheat grains were measured by energy dispersive X-ray fluorescence spectrometry. Large variations in elemental contents were observed among landraces. Marker-based heritability estimates were low to moderate, suggesting that the elemental contents are complex quantitative traits. Genetic correlations between two locations (Japan and Afghanistan) and among the six elements were estimated using a multi-response Bayesian linear mixed model. Low-to-moderate genetic correlations were observed among major elements and among minor elements respectively, but not between major and minor elements. A single-response genome-wide association study detected only one significant marker, which was associated with Zn, suggesting it will be difficult to increase the elemental contents of wheat by conventional marker-assisted selection. Genomic predictions for major elemental contents were moderately or highly accurate, whereas those for minor elements were mostly low or moderate. Our results indicate genomic selection may be useful for the genetic improvement of elemental contents in wheat.

Analysis of grain elements and identification of best genotypes for Fe and P in Afghan wheat landraces

This study was carried out with the aim of developing the methodology to determine elemental composition in wheat and identify the best germplasm for further research. Orphan and genetically diverse Afghan wheat landraces were chosen and EDXRF was used to measure the content of some of the elements to establish elemental composition in grains of 266 landraces using 10 reference lines. Four elements, K, Mg, P, and Fe, were measured by standardizing sample preparation. The results of hierarchical cluster analysis using elemental composition data sets indicated that the Fe content has an opposite pattern to the other elements, especially that of K. By systematic analysis the best wheat germplasms for P content and Fe content were identified. In order to compare the sensitivity of EDXRF, the ICP method was also used and the similar results obtained confirmed the EDXRF methodology. The sampling method for measurement using EDXRF was optimized resulting in high-throughput profiling of elemental composition in wheat grains at low cost. Using this method, we have characterized the Afghan wheat landraces and isolated the best genotypes that have high-elemental content and have the potential to be used in crop improvement.

Overexpression of rice OsREX1-S, encoding a putative component of the core general transcription and DNA repair factor IIH, renders plant cells tolerant to cadmium- and UV-induced damage by enhancing DNA excision repair

Screening of 40,000 Arabidopsis FOX (Full-length cDNA Over-eXpressor gene hunting system) lines expressing rice full-length cDNAs brings us to identify four cadmium (Cd)-tolerant lines, one of which carried OsREX1-S as a transgene. OsREX1-S shows the highest levels of identity to Chlamydomonas reinhardtii REX1-S (referred to as CrREX1-S, in which REX denotes Required for Excision) and to yeast and human TFB5s (RNA polymerase II transcription factor B5), both of which are components of the general transcription and DNA repair factor, TFIIH. Transient expression of OsREX1-S consistently localized the protein to the nucleus of onion cells. The newly generated transgenic Arabidopsis plants expressing OsREX1-S reproducibly displayed enhanced Cd tolerance, confirming that the Cd-tolerance of the initial identified line was conferred solely by OsREX1-S expression. Furthermore, transgenic Arabidopsis plants expressing OsREX1-S exhibited ultraviolet-B (UVB) tolerance by reducing the amounts of cyclobutane pyrimidine dimers produced by UVB radiation. Moreover, those transgenic OsREX1-S Arabidopsis plants became resistant to bleomycin (an inducer of DNA strand break) and mitomycin C (DNA intercalating activity), compared to wild type. Our results indicate that OsREX1-S renders host plants tolerant to Cd, UVB radiation, bleomycin and mitomycin C through the enhanced DNA excision repair.

Identification and characterization of transcription factors regulating Arabidopsis HAK5

Potassium (K) is an essential macronutrient for plant growth and reproduction. HAK5, an Arabidopsis high-affinity K transporter gene, plays an important role in K uptake. Its expression is up-regulated in response to K deprivation and is rapidly down-regulated when sufficient K levels have been re-established. To identify transcription factors regulating HAK5, an Arabidopsis TF FOX (Transcription Factor Full-length cDNA Over-eXpressor) library containing approximately 800 transcription factors was used to transform lines previously transformed with a luciferase reporter gene whose expression was driven by the HAK5 promoter. When grown under sufficient K levels, 87 lines with high luciferase activity were identified, and endogenous HAK5 expression was confirmed in 27 lines. Four lines overexpressing DDF2 (Dwarf and Delayed Flowering 2), JLO (Jagged Lateral Organs), TFII_A (Transcription initiation Factor II_A gamma chain) and bHLH121 (basic Helix-Loop-Helix 121) were chosen for further characterization by luciferase activity, endogenous HAK5 level and root growth in K-deficient conditions. Further analysis showed that the expression of these transcription factors increased in response to low K and salt stress. In comparison with controls, root growth under low K conditions was better in each of these four TF FOX lines. Activation of HAK5 expression by these four transcription factors required at least 310 bp of upstream sequence of the HAK5 promoter. These results indicate that at least these four transcription factors can bind to the HAK5 promoter in response to K limitation and activate HAK5 expression, thus allowing plants to adapt to nutrient stress.

The Arabidopsis COP9 SIGNALOSOME INTERACTING F-BOX KELCH 1 protein forms an SCF ubiquitin ligase and regulates hypocotyl elongation

The regulation of protein turnover by the ubiquitin proteasome system (UPS) is a major posttranslational mechanism in eukaryotes. One of the key components of the UPS, the COP9 signalosome (CSN), regulates 'cullin-ring' E3 ubiquitin ligases. In plants, CSN participates in diverse cellular and developmental processes, ranging from light signaling to cell cycle control. In this work, we isolated a new plant-specific CSN-interacting F-box protein, which we denominated CFK1 (COP9 INTERACTING F-BOX KELCH 1). We show that, in Arabidopsis thaliana, CFK1 is a component of a functional ubiquitin ligase complex. We also show that CFK1 stability is regulated by CSN and by proteasome-dependent proteolysis, and that light induces accumulation of the CFK1 transcript in the hypocotyl. Analysis of CFK1 knockdown, mutant, and overexpressing seedlings indicates that CFK1 promotes hypocotyl elongation by increasing cell size. Reduction of CSN levels enhances the short hypocotyl phenotype of CFK1-depleted seedlings, while complete loss of CSN activity suppresses the long-hypocotyl phenotype of CFK1-overexpressing seedlings. We propose that CFK1 (and its regulation by CSN) is a novel component of the cellular mechanisms controlling hypocotyl elongation.

Role of the rice transcription factor JAmyb in abiotic stress response

Plants have developed certain adaptive responses to environmental stresses that cause adverse effects on growth. To identify genes involved in the adaptive mechanisms, we constructed a large population of transgenic Arabidopsis expressing rice full-length cDNAs, and performed gain-of-function screening under high-salinity stress. In this study, we identified a rice R2R3-type MYB transcription factor gene, JAmyb, as a gene whose overexpression causes tolerance to high salinity. JAmyb overexpression in transgenic Arabidopsis improved tolerance to high-salinity stress during seed germination, seedling growth, and root elongation. In rice seedlings, JAmyb expression was induced by high-salinity and high-osmotic stresses and reactive oxygen species (ROS), suggesting that JAmyb is responsible for abiotic stress response. Microarray analysis showed that the overexpression of JAmyb stimulates the expression of several defense-associated genes, some of which have been predicted to be involved in osmotic adjustment, ROS removal, and ion homeostasis. Several transcription factors involved in the jasmonate (JA)-mediated stress response are also regulated by JAmyb. JAmyb has been reported to be associated with disease response. Our observations suggest that JAmyb plays a role in JA-mediated abiotic stress response in addition to biotic stress response in rice.

Arabidopsis PIZZA has the capacity to acylate brassinosteroids

Brassinosteroids (BRs) affect a wide range of developmental processes in plants and compromised production or signalling of BRs causes severe growth defects. To identify new regulators of plant organ growth, we searched the Arabidopsis FOX (Full-length cDNA Over-eXpressor gene) collection for mutants with altered organ size and isolated two overexpression lines that display typical BR deficient dwarf phenotypes. The phenotype of these lines, caused by an overexpression of a putative acyltransferase gene PIZZA (PIZ), was partly rescued by supplying exogenous brassinolide (BL) and castasterone (CS), indicating that endogenous BR levels are rate-limiting for the growth of PIZ overexpression lines. Our transcript analysis further showed that PIZ overexpression leads to an elevated expression of genes involved in BR biosynthesis and a reduced expression of BR inactivating hydroxylases, a transcriptional response typical to low BR levels. Taking the advantage of relatively high endogenous BR accumulation in a mild bri1-301 background, we found that overexpression of PIZ results in moderately reduced levels of BL and CS and a strong reduction of typhasterol (TY) and 6-deoxocastasterone (6-deoxoCS), suggesting a role of PIZ in BR metabolism. We tested a set of potential substrates in vitro for heterologously expressed PIZ and confirmed its acyltransferase activity with BL, CS and TY. The PIZ gene is expressed in various tissues but as reported for other genes involved in BR metabolism, the loss-of-function mutants did not display obvious growth phenotypes under standard growth conditions. Together, our data suggest that PIZ can modify BRs by acylation and that these properties might help modulating endogenous BR levels in Arabidopsis.

Arabidopsis growth-regulating factor7 functions as a transcriptional repressor of abscisic acid- and osmotic stress-responsive genes, including DREB2A

Arabidopsis thaliana DEHYDRATION-RESPONSIVE ELEMENT BINDING PROTEIN2A (DREB2A) functions as a transcriptional activator that increases tolerance to osmotic and heat stresses; however, its expression also leads to growth retardation and reduced reproduction. To avoid these adverse effects, the expression of DREB2A is predicted to be tightly regulated. We identified a short promoter region of DREB2A that represses its expression under nonstress conditions. Yeast one-hybrid screening for interacting factors identified GROWTH-REGULATING FACTOR7 (GRF7). GRF7 bound to the DREB2A promoter and repressed its expression. In both artificial miRNA-silenced lines and a T-DNA insertion line of GRF7, DREB2A transcription was increased compared with the wild type under nonstress conditions. A previously undiscovered cis-element, GRF7-targeting cis-element (TGTCAGG), was identified as a target sequence of GRF7 in the short promoter region of DREB2A via electrophoretic mobility shift assays. Microarray analysis of GRF7 knockout plants showed that a large number of the upregulated genes in the mutant plants were also responsive to osmotic stress and/or abscisic acid. These results suggest that GRF7 functions as a repressor of a broad range of osmotic stress-responsive genes to prevent growth inhibition under normal conditions.

Characterization of rice genes using a heterologous full-length cDNA expression system

As a result of the progress in sequencing technology, many plant genomes have now been determined. Functional genomics is required to clarify gene function in many of these species. To identify useful genes easily and quickly, we have developed a FOX (full-length cDNA overexpressor) hunting system in which full-length cDNAs are overexpressed in Arabidopsis plants. This system was applied to high-throughput analysis of rice genes through heterologous expression in Arabidopsis (rice FOX Arabidopsis lines). We demonstrated that it is possible to carry out high-throughput analysis of gene function by utilizing rice FOX Arabidopsis lines. In this protocol, we describe how to isolate candidate rice FOX Arabidopsis lines and to determine the rice fl-cDNA that is responsible for the observed phenotype.

Functional analysis of two isoforms of leaf-type ferredoxin-NADP(+)-oxidoreductase in rice using the heterologous expression system of Arabidopsis

Ferredoxin-NADP(+)-oxidoreductase (FNR) mediates electron transfer between ferredoxin (Fd) and NADP(+); therefore, it is a key enzyme that provides the reducing power used in the Calvin cycle. Other than FNR, nitrite reductase, sulfite reductase, glutamate synthase, and Fd-thioredoxin reductase also accept electrons from Fd, an electron carrier protein in the stroma. Therefore, the regulation of electron partitioning in the chloroplast is important for photosynthesis and other metabolic pathways. The regulatory mechanism of electron partitioning, however, remains to be elucidated. We found, by taking advantage of a gain-of-function approach, that expression of two rice (Oryza sativa) full-length cDNAs of leaf-type FNRs (OsLFNR1 and OsLFNR2) led to altered chlorophyll fluorescence and growth in Arabidopsis (Arabidopsis thaliana) and rice. We revealed that overexpression of the OsLFNR1 and OsLFNR2 full-length cDNAs resulted in distinct phenotypes despite the high sequence similarity between them. Expression of OsLFNR1 affected the nitrogen assimilation pathway without inhibition of photosynthesis under normal conditions. On the other hand, OsLFNR2 expression led to the impairment of photosynthetic linear electron transport as well as Fd-dependent cyclic electron flow around photosystem I. The endogenous protein level of OsLFNR was found to be suppressed in both OsLFNR1- and OsLFNR2-overexpressing rice plants, leading to changes in the stoichiometry of the two LFNR isoforms within the thylakoid and soluble fractions. Thus, we propose that the stoichiometry of two LFNR isoforms plays an important role in electron partitioning between carbon fixation and nitrogen assimilation.

Growth arrest by trehalose-6-phosphate: an astonishing case of primary metabolite control over growth by way of the SnRK1 signaling pathway

The strong regulation of plant carbon allocation and growth by trehalose metabolism is important for our understanding of the mechanisms that determine growth and yield, with obvious applications in crop improvement. To gain further insight on the growth arrest by trehalose feeding, we first established that starch-deficient seedlings of the plastidic phosphoglucomutase1 mutant were similarly affected as the wild type on trehalose. Starch accumulation in the source cotyledons, therefore, did not cause starvation and consequent growth arrest in the growing zones. We then screened the FOX collection of Arabidopsis (Arabidopsis thaliana) expressing full-length cDNAs for seedling resistance to 100 mm trehalose. Three independent transgenic lines were identified with dominant segregation of the trehalose resistance trait that overexpress the bZIP11 (for basic region/leucine zipper motif) transcription factor. The resistance of these lines to trehalose could not be explained simply through enhanced trehalase activity or through inhibition of bZIP11 translation. Instead, trehalose-6-phosphate (T6P) accumulation was much increased in bZIP11-overexpressing lines, suggesting that these lines may be insensitive to the effects of T6P. T6P is known to inhibit the central stress-integrating kinase SnRK1 (KIN10) activity. We confirmed that this holds true in extracts from seedlings grown on trehalose, then showed that two independent transgenic lines overexpressing KIN10 were insensitive to trehalose. Moreover, the expression of marker genes known to be jointly controlled by SnRK1 activity and bZIP11 was consistent with low SnRK1 or bZIP11 activity in seedlings on trehalose. These results reveal an astonishing case of primary metabolite control over growth by way of the SnRK1 signaling pathway involving T6P, SnRK1, and bZIP11.

Screening for resistance against Pseudomonas syringae in rice-FOX Arabidopsis lines identified a putative receptor-like cytoplasmic kinase gene that confers resistance to major bacterial and fungal pathogens in Arabidopsis and rice

Approximately 20,000 of the rice-FOX Arabidopsis transgenic lines, which overexpress 13,000 rice full-length cDNAs at random in Arabidopsis, were screened for bacterial disease resistance by dip inoculation with Pseudomonas syringae pv. tomato DC3000 (Pst DC3000). The identities of the overexpressed genes were determined in 72 lines that showed consistent resistance after three independent screens. Pst DC3000 resistance was verified for 19 genes by characterizing other independent Arabidopsis lines for the same genes in the original rice-FOX hunting population or obtained by reintroducing the genes into ecotype Columbia by floral dip transformation. Thirteen lines of these 72 selections were also resistant to the fungal pathogen Colletotrichum higginsianum. Eight genes that conferred resistance to Pst DC3000 in Arabidopsis have been introduced into rice for overexpression, and transformants were evaluated for resistance to the rice bacterial pathogen, Xanthomonas oryzae pv. oryzae. One of the transgenic rice lines was highly resistant to Xanthomonas oryzae pv. oryzae. Interestingly, this line also showed remarkably high resistance to Magnaporthe grisea, the fungal pathogen causing rice blast, which is the most devastating rice disease in many countries. The causal rice gene, encoding a putative receptor-like cytoplasmic kinase, was therefore designated as BROAD-SPECTRUM RESISTANCE 1. Our results demonstrate the utility of the rice-FOX Arabidopsis lines as a tool for the identification of genes involved in plant defence and suggest the presence of a defence mechanism common between monocots and dicots.

A high-throughput screening system for Arabidopsis transcription factors and its application to Med25-dependent transcriptional regulation

The activities of transcription factors (TFs) require interactions with specific DNA sequences and other regulatory proteins. To detect such interactions in Arabidopsis, we developed a high-throughput screening system with a Gateway-compatible Gal4-AD-TF library of 1589 Arabidopsis TFs, which can be easily screened by mating-based yeast-one-hybrid (Y1H) and yeast-two-hybrid (Y2H) methods. The efficiency of the system was validated by examining two well-characterized TF-DNA and TF-protein interactions: the CHE-CCA1 promoter interaction by Y1H and NPR1-TGAs interactions by Y2H. We used this system to identify eight TFs that interact with a Mediator subunit, Med25, a key regulator in JA signaling. We identified five TFs that interacted with the GCC-box cis-element in the promoter of PDF1.2, a downstream gene of Med25. We found that three of these TFs, all from the AP2-EREBP family, interact directly both with Med25 and the GCC-box of PDF1.2, suggesting that Med25 regulates PDF1.2 expression through these three TFs. These results demonstrate that this high-throughput Y1H/Y2H screening system is an efficient tool for studying transcriptional regulation networks in Arabidopsis. This system will be available for other Arabidopsis researchers, and thus it provides a vital resource for the Arabidopsis community.

RiceFOX: a database of Arabidopsis mutant lines overexpressing rice full-length cDNA that contains a wide range of trait information to facilitate analysis of gene function

Identification of gene function is important not only for basic research but also for applied science, especially with regard to improvements in crop production. For rapid and efficient elucidation of useful traits, we developed a system named FOX hunting (Full-length cDNA Over-eXpressor gene hunting) using full-length cDNAs (fl-cDNAs). A heterologous expression approach provides a solution for the high-throughput characterization of gene functions in agricultural plant species. Since fl-cDNAs contain all the information of functional mRNAs and proteins, we introduced rice fl-cDNAs into Arabidopsis plants for systematic gain-of-function mutation. We generated >30,000 independent Arabidopsis transgenic lines expressing rice fl-cDNAs (rice FOX Arabidopsis mutant lines). These rice FOX Arabidopsis lines were screened systematically for various criteria such as morphology, photosynthesis, UV resistance, element composition, plant hormone profile, metabolite profile/fingerprinting, bacterial resistance, and heat and salt tolerance. The information obtained from these screenings was compiled into a database named 'RiceFOX'. This database contains around 18,000 records of rice FOX Arabidopsis lines and allows users to search against all the observed results, ranging from morphological to invisible traits. The number of searchable items is approximately 100; moreover, the rice FOX Arabidopsis lines can be searched by rice and Arabidopsis gene/protein identifiers, sequence similarity to the introduced rice fl-cDNA and traits. The RiceFOX database is available at http://ricefox.psc.riken.jp/.

A novel chloroplast protein, CEST induces tolerance to multiple environmental stresses and reduces photooxidative damage in transgenic Arabidopsis

Environmental stresses are major factors in limiting plant growth and crop production. To find genes improving salt tolerance, the screening of a large population of transgenic Arabidopsis thaliana that expressed rice full-length cDNAs under salinity stress is reported here. In this study one of the isolated salt-tolerant lines, R07303 was analysed in detail. An uncharacterized rice gene CHLOROPLAST PROTEIN-ENHANCING STRESS TOLERANCE (OsCEST) was integrated in R07303. Newly constructed transgenic Arabidopsis that overexpressed OsCEST or its Arabidopsis homologue AtCEST showed improved tolerance to salinity stress. OsCEST and AtCEST were mainly transcribed in photosynthetic tissues. Green fluorescent protein-fused OsCEST and AtCEST proteins were localized to the chloroplast in the Arabidopsis leaf protoplasts. CEST-overexpressing Arabidopsis showed enhanced tolerance not only to salt stress but also to drought stress, high-temperature stress, and paraquat, which causes photooxidative stress. Under saline conditions, overexpression of CESTs modulated the stress-induced impairment of photosynthetic activity and the peroxidation of lipids. Reduced expression of AtCEST because of double-stranded RNA interference resulted in the impairment of photosynthetic activity, the reduction of green pigment, defects in chloroplast development, and growth retardation under light. This paper discusses the relationship between the chloroplast protein CEST and photooxidative damage.

Full-length cDNA overexpressor gene hunting system (FOX hunting system)

Full-length cDNAs (fl-cDNAs) are important resources for the characterization of gene function, since they contain all the information required for the production of functional RNAs and proteins. Large sets of fl-cDNA clones have been collected from several plant species and have become available for functional genomic analysis. We have developed a system for the identification of gene function by screening for transgenic plants ectopically expressing fl-cDNAs and named it the FOX (fl-cDNA overexpressor gene) hunting system. This system can be applied to almost all plant species without prior knowledge of their genome sequences because only fl-cDNAs are required. For utilization of the FOX hunting system, Agrobacterium libraries and Arabidopsis seeds carrying rice and Arabidopsis fl-cDNAs are available. Here, we will describe the procedure followed in the FOX hunting system from the generation of expression vectors carrying fl-cDNAs to the confirmation of phenotype in retransformed plants.

Application of full-length cDNA resources to gain-of-function technology for characterization of plant gene function

Generation and characterization of mutants are important for the investigation of gene function. Gain-of-function technology is one of the most useful approaches for the systematic production of mutant resources. Full-length cDNAs have been collected from various plant species and have become important resources for functional genomics. We have developed a novel gain-of-function technology for the identification of gene function using a full-length cDNA library, and this system has been named as FOX hunting system (Full-length cDNA Over-eXpressing gene hunting system). In this system, full-length cDNAs are randomly expressed in Arabidopsis. We also generated rice FOX Arabidopsis lines in which full-length cDNAs from rice were expressed in Arabidopsis, and we demonstrated that gene function derived from heterologous organisms can be analyzed systematically using the FOX hunting approach. In this protocol, we describe the process of generating Arabidopsis mutants expressing rice full-length cDNA libraries and the methods of identifying genes from the isolated mutants.

Efficient yeast one-/two-hybrid screening using a library composed only of transcription factors in Arabidopsis thaliana

Yeast one-hybrid screening is widely used for the identification of transcription factors (TFs) that interact with specific DNA sequences. However, screening a whole cDNA library is not efficient for the identification of TFs because TF genes represent only a small percentage of clones in a cDNA library. Here, we present the development of an efficient yeast one-hybrid screening system using a prey library composed only of approximately 1,500 TF cDNAs of Arabidopsis thaliana. This library enabled us to isolate a TF that binds to a specific promoter sequence with high efficiency, even when the promoter region of the gene of interest was directly employed as bait. Furthermore, this library was also successfully applied as a yeast two-hybrid library to find TFs that interact with specific proteins. This efficient system will contribute to the elucidation of gene regulatory networks in plants.

The YlmG protein has a conserved function related to the distribution of nucleoids in chloroplasts and cyanobacteria

BACKGROUND

Reminiscent of their free-living cyanobacterial ancestor, chloroplasts proliferate by division coupled with the partition of nucleoids (DNA-protein complexes). Division of the chloroplast envelope membrane is performed by constriction of the ring structures at the division site. During division, nucleoids also change their shape and are distributed essentially equally to the daughter chloroplasts. Although several components of the envelope division machinery have been identified and characterized, little is known about the molecular components/mechanisms underlying the change of the nucleoid structure.

RESULTS

In order to identify new factors that are involved in the chloroplast division, we isolated Arabidopsis thaliana chloroplast division mutants from a pool of random cDNA-overexpressed lines. We found that the overexpression of a previously uncharacterized gene (AtYLMG1-1) of cyanobacterial origin results in the formation of an irregular network of chloroplast nucleoids, along with a defect in chloroplast division. In contrast, knockdown of AtYLMG1-1 resulted in a concentration of the nucleoids into a few large structures, but did not affect chloroplast division. Immunofluorescence microscopy showed that AtYLMG1-1 localizes in small puncta on thylakoid membranes, to which a subset of nucleoids colocalize. In addition, in the cyanobacterium Synechococcus elongates, overexpression and deletion of ylmG also displayed defects in nucleoid structure and cell division.

CONCLUSIONS

These results suggest that the proper distribution of nucleoids requires the YlmG protein, and the mechanism is conserved between cyanobacteria and chloroplasts. Given that ylmG exists in a cell division gene cluster downstream of ftsZ in gram-positive bacteria and that ylmG overexpression impaired the chloroplast division, the nucleoid partitioning by YlmG might be related to chloroplast and cyanobacterial division processes.

High-throughput characterization of plant gene functions by using gain-of-function technology

Gain-of-function approaches have been used as an alternative or complementary method to loss-of-function approaches as well as to confer new functions to plants. Gain-of-function is achieved by increasing gene expression levels through the random activation of endogenous genes by transcriptional enhancers or the expression of individual transgenes by transformation. The advantages of gain-of-function approaches compared to loss-of-function approaches for the characterization of gene functions include the abilities to (a) analyze individual gene family members, (b) characterize the function of genes from nonmodel plants using a heterologous expression system, and (c) identify genes that confer stress tolerance to plants that result from the introduction of transgenes. In this review, we describe the current status of gain-of-function mutagenesis and provide several examples of how gene functions have been characterized via high-throughput screening using gain-of-function technology.

Overexpression of a rice gene encoding a small C2 domain protein OsSMCP1 increases tolerance to abiotic and biotic stresses in transgenic Arabidopsis

Plant growth and crop production are limited by environmental stress. We used a large population of transgenic Arabidopsis expressing rice full-length cDNAs to isolate the rice genes that improve the tolerance of plants to environmental stress. By sowing T2 seeds of the transgenic lines under conditions of salinity stress, the salt-tolerant line R07047 was isolated. It expressed a rice gene, OsSMCP1, which encodes a small protein with a single C2 domain, a Ca(2+)-dependent membrane-targeting domain. Retransformation of wild-type Arabidopsis revealed that OsSMCP1 is responsible for conferring the salt tolerance. It is particularly interesting that R07047 and newly constructed OsSMCP1-overexpressing Arabidopsis showed enhanced tolerance not only to high salinity but also to osmotic, dehydrative, and oxidative stresses. Furthermore, R07047 showed improved resistance to Pseudomonas syringae. The OsSMCP1 expression in rice is constitutive. Particle-bombardment-mediated transient expression analysis revealed that OsSMCP1 is targeted to plastids in rice epidermal cells. It induced overexpression of several nuclear encoded genes, including the stress-associated genes, in transgenic Arabidopsis. No marked morphological change or growth retardation was observed in R07047 or retransformants. For molecular breeding to improve the tolerance of crops against environmental stress, OsSMCP1 is a promising candidate.

The trihelix transcription factor GTL1 regulates ploidy-dependent cell growth in the Arabidopsis trichome

Leaf trichomes in Arabidopsis thaliana develop through several distinct cellular processes, such as patterning, differentiation, and growth. Although recent studies have identified several key transcription factors as regulating early patterning and differentiation steps, it is still largely unknown how these regulatory proteins mediate subsequent trichome development, which is accompanied by rapid cell growth and branching. Here, we report a novel trichome mutation in Arabidopsis, which in contrast with previously identified mutants, increases trichome cell size without altering its overall patterning or branching. We show that the corresponding gene encodes a GT-2-LIKE1 (GTL1) protein, a member of the trihelix transcription factor family. GTL1 is present within the nucleus during the postbranching stages of trichome development, and its loss of function leads to an increase in the nuclear DNA content only in trichomes that have completed branching. Our data further demonstrate that the gtl1 mutation modifies the expression of several cell cycle genes and partially rescues the ploidy defects in the cyclin-dependent kinase inhibitor mutant siamese. Taken together, this study provides the genetic evidence for the requirement of transcriptional regulation in the repression of ploidy-dependent plant cell growth as well as for an involvement of GTL trihelix proteins in this regulation.

Phenome analysis in plant species using loss-of-function and gain-of-function mutants

Analysis of genetic mutations is one of the most effective ways to investigate gene function. We now have methods that allow for mass production of mutant lines and cells in a variety of model species. Recently, large numbers of mutant lines have been generated by both 'loss-of-function' and 'gain-of-function' techniques. In parallel, phenotypic information covering various mutant resources has been acquired and released in web-based databases. As a result, significant progress in comprehensive phenotype analysis is being made through the use of these tools. Arabidopsis and rice are two major model plant species in which genome sequencing projects have been completed. Arabidopsis is the most widely used experimental plant, with a large number of mutant resources and several examples of systematic phenotype analysis. Rice is a major crop species and is used as a model plant, with an increasing number of mutant resources. Other plant species are also being employed in functional genetics research. In this review, the present status of mutant resources for large-scale studies of gene function in plant research and the current perspective on using loss-of-function and gain-of-function mutants in phenome research will be discussed.

Tolerance to various environmental stresses conferred by the salt-responsive rice gene ONAC063 in transgenic Arabidopsis

Environmental stresses limit plant growth and crop production worldwide. We attempted to isolate rice genes involved in conferring tolerance to environmental stresses by using a transgenic Arabidopsis population expressing full-length cDNAs of rice. Among these lines, a thermotolerant line, R08946, was detected. The rice cDNA inserted in R08946 encoded a NAC transcription factor, ONAC063. This protein was localized in the nucleus and showed transactivation activity at the C-terminus. ONAC063 expression was not induced by high-temperature but highly induced by high-salinity in rice roots. High-osmotic pressure and reactive oxygen species levels also induced ONAC063 expression. The seeds of ONAC063-expressing transgenic Arabidopsis showed enhanced tolerance to high-salinity and osmotic pressure. Microarray and real-time reverse transcription-polymerase chain reaction analyses showed upregulated expression of some salinity-inducible genes, including the amylase gene AMY1, in ONAC063-expressing transgenic Arabidopsis. Thus, ONAC063 may play an important role in eliciting responses to high-salinity stress.

Systematic approaches to using the FOX hunting system to identify useful rice genes

Ectopic gene expression, or the gain-of-function approach, has the advantage that once the function of a gene is known the gene can be transferred to many different plants by transformation. We previously reported a method, called FOX hunting, that involves ectopic expression of Arabidopsis full-length cDNAs in Arabidopsis to systematically generate gain-of-function mutants. This technology is most beneficial for generating a heterologous gene resource for analysis of useful plant gene functions. As an initial model we generated more than 23,000 independent Arabidopsis transgenic lines that expressed rice fl-cDNAs (Rice FOX Arabidopsis lines). The short generation time and rapid and efficient transformation frequency of Arabidopsis enabled the functions of the rice genes to be analyzed rapidly. We screened rice FOX Arabidopsis lines for alterations in morphology, photosynthesis, element accumulation, pigment accumulation, hormone profiles, secondary metabolites, pathogen resistance, salt tolerance, UV signaling, high light tolerance, and heat stress tolerance. Some of the mutant phenotypes displayed by rice FOX Arabidopsis lines resulted from the expression of rice genes that had no homologs in Arabidopsis. This result demonstrated that rice fl-cDNAs could be used to introduce new gene functions in Arabidopsis. Furthermore, these findings showed that rice gene function could be analyzed by employing Arabidopsis as a heterologous host. This technology provides a framework for the analysis of plant gene function in a heterologous host and of plant improvement by using heterologous gene resources.

RETARDED GROWTH OF EMBRYO1, a new basic helix-loop-helix protein, expresses in endosperm to control embryo growth

We have isolated two dominant mutants from screening approximately 50,000 RIKEN activation-tagging lines that have short inflorescence internodes. The activation T-DNAs were inserted near a putative basic helix-loop-helix (bHLH) gene and expression of this gene was increased in the mutant lines. Overexpression of this bHLH gene produced the original mutant phenotype, indicating it was responsible for the mutants. Specific expression was observed during seed development. The loss-of-function mutation of the RETARDED GROWTH OF EMBRYO1 (RGE1) gene caused small and shriveled seeds. The embryo of the loss-of-function mutant showed retarded growth after the heart stage although abnormal morphogenesis and pattern formation of the embryo and endosperm was not observed. We named this bHLH gene RGE1. RGE1 expression was determined in endosperm cells using the beta-glucuronidase reporter gene and reverse transcription-polymerase chain reaction. Microarray and real-time reverse transcription-polymerase chain reaction analysis showed specific down-regulation of putative GDSL motif lipase genes in the rge1-1 mutant, indicating possible involvement of these genes in seed morphology. These data suggest that RGE1 expression in the endosperm at the heart stage of embryo development plays an important role in controlling embryo growth.

Expression of rice heat stress transcription factor OsHsfA2e enhances tolerance to environmental stresses in transgenic Arabidopsis

Plant growth and crop yields are limited by high-temperature stresses. In this study, we attempted to isolate the rice genes responsible for high-temperature stress tolerance using a transformed Arabidopsis population expressing a full-length cDNA library of rice. From approximately 20,000 lines of transgenic Arabidopsis, we isolated a thermotolerant line, R04333, that could survive transient heat stress at the cotyledon stage. The rice cDNA inserted in R04333 encodes OsHsfA2e, a member of the heat stress transcription factors. The thermotolerant phenotype was observed in newly constructed transgenic Arabidopsis plants expressing OsHsfA2e. Among 5 A2-type HSF genes encoded in the rice genome, four genes, including OsHsfA2e, are induced by high temperatures in rice seedlings. The OsHsfA2e protein was localized to the nuclear region and exhibited transcription activation activity in the C-terminal region. Microarray analysis demonstrated that under unstressed conditions transgenic Arabidopsis overexpressing OsHsfA2e highly expressed certain stress-associated genes, including several classes of heat-shock proteins. The thermotolerant phenotype was observed not only in the cotyledons but also in rosette leaves, inflorescence stems and seeds. In addition, transgenic Arabidopsis exhibited tolerance to high-salinity stress. These observations suggest that the OsHsfA2e may be useful in molecular breeding designed to improve the environmental stress tolerance of crops.

The FOX hunting system: an alternative gain-of-function gene hunting technique

We have developed a novel gain-of-function system that we have named the FOX hunting system (Full-length cDNA Over-eXpressing gene hunting system). We used normalized full-length cDNA and introduced each cDNA into Arabidopsis by in planta transformation. About 10 000 independent full-length Arabidopsis cDNAs were expressed independently under the CaMV 35S promoter in Arabidopsis. Each transgenic Arabidopsis contained on average 2.6 cDNA clones and was monitored under various categories such as morphological changes, fertility and leaf color. We found 1487 possible morphological mutants from 15 547 transformants. When 115 pale green T(1) mutants were analyzed, 59 lines represented the mutant phenotypes in more than 50% of the T(2) progeny. Characterization of two leaf color mutants revealed the significance of this approach. We also document mutants from several categories and their corresponding full-length cDNAs.

Bipolar localization of putative photoreceptor protein for phototaxis in thermophilic cyanobacterium Synechococcus elongatus

We identified an open reading frame from a database of the entire genome of Synechococcus elongatus, the product of which was very similar to pixJ1, which was proposed as photoreceptor gene for phototaxis in Synechocystis sp. PCC6803 [Yoshihara et al. (2000) Plant Cell Physiol. 41: 1299]. The mRNA of S. elongatus pixJ (SepixJ) was expressed in vivo as a part of the product of an operon. SePixJ was detected exclusively in the membrane fraction after cell fractionation. Immunogold labeling of SePixJ in ultra-thin sections indicated that it existed only in both ends of the rod-shaped cell; probably bound with the cytoplasmic membrane.

Equal-quantum action spectra indicate fluence-rate-selective action of multiple photoreceptors for photomovement of the thermophilic cyanobacterium Synechococcus elongatus

Unicellular thermophilic cyanobacterium Synechococcus elongatus displayed phototaxis on agar plate at 55 degrees C. Equal-quantum action spectra for phototactic migration were determined at various fluence rates using the Okazaki Large Spectrograph as the light source. The shapes of the action spectra drastically changed depending on the fluence rate of the unilateral monochromatic irradiation: at a low fluence rate (3 mumol/m2/s), only lights in the red region had significant effect; at a medium fluence rate (10 mumol/m2/s), four major action peaks were observed at 530 nm (green), 570 nm (yellow), 640 nm (red) and 680 nm (red). At high fluence rates (30-90 mumol/m2/s), the former two peaks remained, while red peaks at 640 nm and 680 nm disappeared and, interestingly, an action peak around 700-740 nm (far-red) newly appeared. These results indicate that two or more distinct photoreceptors are involved in the phototaxis and that suitable photoreceptors are selectively active in response to the stimulus of light fluence rates. Far-red or red background lights irradiated vertically from above drastically inhibited phototaxis toward red light or far-red light, respectively. These results indicate involvement of some phytochrome(s).

A new erythrocyte fragility test: a simple procedure utilizing stirring

In this study, a new simple method to measure erythrocyte fragility with stirring of diluted blood (stirring method) was introduced and evaluated with anemic rats given beta-acetylphenylhydrazine (APHZ) or clofibrate. APHZ at a dose of 40 mg/kg caused significant decreases in hemoglobin and hematocrit 24 hr after administration. However, the marked elevation of erythrocyte fragility was already detectable after 6 hr by our stirring method. At a dose of 10 mg/kg APHZ, although no significant changes in the erythrocytic parameters were observed throughout the experimental period (72 hr), the blood stirring method revealed a marked elevation of erythrocyte fragility 6 hr after administration. Similarly with clofibrate, no changes in erythrocytic parameters were noted following 100 mg/kg or 300 mg/kg administration, but the enhanced fragility was evident with the stirring method. Thus, using our approach, the erythrocyte fragility could be detected at an earlier stage and with greater sensitivity than by decreases in erythrocytic parameters. The results suggest that the stirring method will prove to be useful for detecting erythrocyte fragility in safety studies.

[Successful use of angiotensin II receptor antagonist (losartan) in a patient with scleroderma renal crisis]

A 67-year-old man with a one-and-a half-year history of Raynaud's phenomenon was admitted to our hospital for progressive dyspnea occurring over the previous two weeks. Physical examination revealed a blood pressure of 200/124 mmHg, and slightly tight and smooth skin of the fingers, hands and forearms. Laboratory evaluation included serum creatinine of 5.42 mg/dl, plasma renin activity > 20 ng/ml/hr, and antinuclear antibody with a titer of 1 : 1,280. Renal biopsy was performed and the histopathological findings showed that some glomeruli exhibited ischemic retraction with wrinkling of the basement membranes, and that one arteriole exhibited significant intimal hyperplasia with luminal stenosis. These findings were compatible with scleroderma renal crisis (SRC). On the 5th day, serum creatinine had risen to 9.16 mg/dl, and he required temporary hemodialysis therapy. After the administration of captopril was started, his blood pressure fell to 160/86 mmHg and serum creatinine was reduced to 5.12 mg/dl. On the 9th day, he exhibited skin eruptions, and captopril was discontinued accordingly and temocapril started. Because of continued eruptions, temocapril was replaced by losartan. His blood pressure was controlled easily and his serum creatinine level reduced steadily. One year after the start of losartan, serum creatinine was 2.25 mg/dl and blood pressure was 130/82 mmHg. SRC is a life-threatening manifestation of systemic sclerosis. In the late 1970s, angiotensin converting enzyme (ACE) inhibitor was introduced and has dramatically improved the outcome in SRC patients. As ACE inhibitors act mainly on hyperreninemic renal vasoconstrictive hypertension in SRC, we would expect losartan, a selective antagonist of angiotensin receptor subtype 1, to be interchangeable with ACE inhibitors in SRC. In 1997, Caskey and colleagues reported the failure of losartan to control hypertension in a patient of SRC, and the reason has remained unclear. We report here, a case of SRC whose blood pressure was controlled successfully and his renal failure reversed by the administration of losartan.

COLLABORATIVE WORK TO EVALUATE TOXICITY ON MALE REPRODUCTIVE ORGANS BY REPEATED DOSE STUDIES IN RATS : 26)DETECTION OF 1, 3-DINITROBENZENE-INDUCED HISTOPATHOLOGICAL CHANGES IN TESTES AND EPIDIDYMIDES OF RATS WITH 2-WEEK DAILY REPEATED DOSING

As part of a collaborative work, male rats were administered 1,3-dinitrobenzene (1,3-DNB) daily at 0, 25 and 50 mg/kg/day from the age of 6 weeks for 4 weeks (4-week exp.), or at 25, 50 and 75 mg/kg/day from the age of 8 weeks for 2 weeks (2-week exp.). After the end of each administration period, all survivors were sacrificed, and their testes and epididymides were removed, weighed and examined histopathologically. The following results were obtained. In the 4-week exp.: At 50 mg/kg/day, the weights of testes and epididymides showed decrease with macroscopic atrophy. The testicular spermatogenic epithelium showed decrease in the number of sperm-spermatocytes, degeneration/necrosis, giant cell formation and vacuolation, reduction in sperm counts also being evident in the ducts of the epididymides. In the 2-week exp.: At 50 and 75 mg/kg/day, the weights of testes and/or epididymides showed decrease with macroscopic atrophy. Several histopathological changes in the testes and epididymides were essentially the same changes as in the group given 50 mg/kg/day in the 4-week exp., with a clear relation. These results indicate that a 2-week administration period is sufficient to detect testicular and epididymal histopathological changes induced by 1,3-dinitrobenzene in male rats.

[Studies on the conditions of blood sampling and storage for the liposome-based CH50 assay]

The CH50 values in the serum and plasma, especially those from chronic hepatitis caused by hepatitis C virus (HCV), are strongly affected and reduced through a process known as cold activation. We attempted to optimize the conditions of blood sampling and storage for the CH50 assay with a recently developed liposome-based assay kit. The bloods were obtained from HCV hepatitis patients as well as healthy donors. Regardless of the temperature (room temperature, 4 degrees C or 37 degrees C) at which samples were kept until the assay, higher values were always obtained in the serum than in the plasma. The plasma samples could either be heparinized or given any of the other anticoagulants, EDTA-2K and sodium citrate, at the time of sampling. We also attempted to optimize the temperature at which the fresh specimens were left during the period from sampling to assay and the temperatures to freeze them for storage and to thaw for assays. In the assays immediately after sampling, higher values were obtained when the specimens were left at 37 degrees C than at room temperature or 4 degrees C. To store at -80 degrees C rather than at -20 degrees C and to thaw rapidly at 37 degrees C rather than slowly at room temperature were found to be advantageous.

[Sudden cardiac tamponade due to hemorrhagic myocarditis after preconditioning marrow transplantation with cyclophosphamide in a patient with aplastic anemia]

A 28-year-old male was diagnosed as aplastic anemia in 1983. He maintained on corticosterone with a large transfusion requirement for being resistant to other therapies, and combined with hemochromatosis at 20-year-old. In February 1994, he was admitted to the hospital for consideration of BMT. Echocardiogram was normal on admission. He was transplanted with bone marrow from his HLA-matched MLC negative sister following contained of TLI (7.5 Gy) and CY 50 mg/kg for four days on March 10 1994. Disturbance of consciousness appeared, an echocardiogram showed severe pericardial effusion on day 1 after BMT. He was diagnosed cardiac tamponade, pericardiocentesis was done immediately and 100 ml pericardial effusion was removed. Transiently he became alert, however, irreversible cardiac arrest occurred on day 2. Postmortem examination revealed thickened left ventricles with intramyocardial hemorrhage. It seems necessary to reduce CY, or substitute it with anti-thymocyte globulin (ATG) or TBI etc. for BMT in aplastic anemia accompanied by hemochromatosis.

Inactivation of a novel neuropeptide Y/peptide YY receptor gene in primate species

Neuropeptide Y (NPY), peptide YY (PYY), and pancreatic polypeptide (PP) belong to a family of structurally related peptides which have numerous functions in both neural and endocrine signaling. By homology screening, we cloned a novel gene sharing the highest homology with the NPY Y1 receptor gene from humans, rabbits, and several other species. This novel gene of rabbit encodes a functional NPY/PYY receptor, designated Y2b, which prefers NPY13-36 rather than [Leu31,Pro34]NPY despite its higher identity with the Y1 receptor. Although, at low levels, mRNA was detected in the tissues and brain regions, including hypothalamus. Further, sequence data revealed that this gene is the orthologue of the recently cloned mouse novel NPY receptor, Y5. However, our study demonstrates that the receptor function of this gene has been inactivated in primates by a frameshift mutation occurring early in primate evolution. This novel NPY receptor represents the first neurotransmitter receptor identified that has universally lost its receptor function in primate species. Interestingly, despite its inactivation in humans, the transcripts were abundantly detected in the heart and skeletal muscle, suggesting a novel function of the human gene.

[Histological effects of short term endocrine therapy on prostatic cancer]

BACKGROUND

The objective of this study is to investigate the pathological changes which occurred in prostatic cancer shortly after the commencement of endocrine therapy.

METHODS

Fourty-three patients underwent radical prostatectomy immediately after the short term endocrine therapy (treatment period was within one month) and the histological pictures of operative specimens were compared to those obtained from the pretreatment biopsy specimens.

RESULTS

Degenerative changes of cancer cells, such as nuclear and cytoplasmic vacuole, collapse of the cytoplasm and the appearance of naked hyperchromatic nucleus were noticed after the short term endocrine therapy. Especially in the cases which were histologically evaluated to be poorly differentiated in the biopsy specimens, not only degenerative changes but also destruction of cancer nests caused by cell death were observed. The histological effects affected by short term endocrine treatment had no relation to the prognosis, but in the cases of stage D2, the pathological grade judged by post-therapeutic specimens were found to be useful for the prediction of prognosis.

CONCLUSION

Endocrine therapy induces remarkable pathological changes in prostatic cancer within a very short time after beginning treatment.

[Immediate hypersensitive reactions to the ingestion of egg white and IgE binding to the egg white components]

IgE is considered to be involved in immediate hypersensitive reactions (IHR) following egg ingestion. IgE antibody levels to egg-white (EW) antigens in the IHR-positive group (n = 19, mean age +/- SD = 5.2 +/- 4.5 yr) were higher than those in the IHR-negative group (n = 13, mean of age +/- SD = 3.6 +/- 2.2 yr). However, even in the IHR-negative group, some patients showed high IgE to EW. RAST inhibition tests with heat-treated (100 degrees C, 5, 10, and 30 min) egg-white antigens were performed on 13 serum samples from subjects with IHR and 9 serum samples from subjects without IHR. Heat treatment decreased the IgE-binding activity of egg white and it was speculated that IgE from IHR-negative subjects bound to relatively heat-unstable sites of egg-white antigens. Furthermore, we selected IHR-negative subjects (n = 8, mean of age +/- SD = 3.0 +/- 1.7 yr) with higher IgE antibody levels than the lowest limit of IgE to EW of the IHR-positive group and compared IgE to ovomucoid (OM), ovalbumin (OA), conalbumin (CA), and lysozyme (Ly) between these IHR-negative and positive groups. IgE-binding activities to egg-white components, including OA, CA, and Ly but not OM, were significantly decreased with heat treatment. The IHR-negative group showed significantly lower IgE to OM (untreated, 5, 10, 30 min treatment) and 5 min treated OA alone than the IHR-positive group, while no difference was found in IgE to other components between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of dissolution of collagen on adhesion to dentin

A new method of adherend surface treatment was evaluated to determine the effect of adhesion between dentin and adhesive resins. The pretreatment method consisted of the application of 40% phosphoric acid solution to dentin to remove the smear layer and decalcify the superficial dentin layer, followed by 10% sodium hypochlorite to dissolve and remove the exposed dentinal collagen and provide a fresh dentin apatite surface to which adhesive resin is applied. This method features a direct adhesion between the adhesive resin and dentin, with no resin-reinforced layer of dentinal collagen and adhesive resin. The adhesive tensile strength after storage in water at 37 degrees C for 24 hours measured 6.7 MPa with the phosphoric acid treatment alone, while the test method produced an initial adhesive strength as high as 9.7 MPa. After 10,000 thermal cycles (4 degrees C to 60 degrees C), the adhesive strength was 6.2 MPa, which was approximately 1.5 times greater than the value obtained with the method using the phosphoric acid solution alone.

[Two cases of primary sclerosing lipogranuloma in scrotum--review of 63 cases reported in Japan]

We reported two cases of primary sclerosing lipogranuloma in the scrotum. We performed tumor resection in both cases, but in one of the two cases tumor recurrence was observed 7 days after the removal. Sixty-three cases have been reported in our country, and we discuss the diagnosis and treatment with reference to previous reports.

[Cross-allergenicity between rice and buckwheat antigens and immediate hypersensitive reactions induced by buckwheat ingestion]

Immediate hypersensitive reactions (IHR) induced by buckwheat ingestion are considered to be IgE-mediated. However we found 28 subjects without IHR to buckwheat ingestion out of 46 subjects who had positive RAST values for both buckwheat and rice antigens. The IHR-positive group showed significantly higher RAST values for buckwheat antigens (p < 0.01) but lower RAST values for rice antigens (p < 0.01) than did the IHR-negative group. RAST values for buckwheat and rice were significantly correlated with each other (p < 0.01) in the IHR-negative group, but not in the IHR-positive group. An effective dose-dependent inhibition was obtained in a RAST inhibition assay between homologous combinations of inhibitor and disc antigens such as rice and rice or buckwheat and buckwheat. The IHR-positive group showed no significant RAST inhibition between heterogeneous combinations of rice and buckwheat antigens. In contrast, the IHR-negative group showed a significant decrease in IgE binding even in the RAST inhibition assay between heterogenous combinations. These results led to the conclusion that there is cross-reactivity with IgE antibodies between buckwheat and rice and that IgE antibodies from IHR-negative subjects might recognize the epitopes on buckwheat antigens which cross react with rice antigens, whereas IgE antibodies from IHR-positive subjects might bind to buckwheat-specific epitopes.