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Background: Root system architecture is an important trait affecting the uptake of nutrients and water by crops. Shallower root systems preferentially take up nutrients from the topsoil and help avoid unfavorable environments in deeper soil layers. We have found a soil-surface rooting mutant from an M 2 population that was regenerated from seed calli of a japonica rice cultivar, Nipponbare. In this study, we examined the genetic and physiological characteristics of this mutant. Results: The primary roots of the mutant showed no gravitropic response from the seedling stage on, whereas the gravitropic response of the shoots was normal. Segregation analyses by using an F 2 population derived from a cross between the soil-surface rooting mutant and wild-type Nipponbare indicated that the trait was controlled by a single recessive gene, designated as sor1. Fine mapping by using an F 2 population derived from a cross between the mutant and an indica rice cultivar, Kasalath, revealed that sor1 was located within a 136-kb region between the simple sequence repeat markers RM16254 and 2935-6 on the terminal region of the short arm of chromosome 4, where 13 putative open reading frames (ORFs) were found. We sequenced these ORFs and detected a 33-bp deletion in one of them, Os04g0101800. Transgenic plants of the mutant transformed with the genomic fragment carrying the Os04g0101800 sequence from Nipponbare showed normal gravitropic responses and no soil-surface rooting. Conclusion: These results suggest that sor1, a rice mutant causing soil-surface rooting and altered root gravitropic response, is allelic to Os04g0101800, and that a 33-bp deletion in the coding region of this gene causes the mutant phenotypes. [ABSTRACT FROM AUTHOR]

Microphthalmia-associated transcription factor (Mitf) is a regulator for differentiation of melanoblasts that are derived from the neural crest. The mouse homozygous for the black-eyed white ( Mitf mi-bw) allele is characterized by the white coat color and deafness, with black eye that is associated with the lack of melanocytes in skin and inner ear. The Mitf mi-bw mutation is an insertion of the LINE1 retrotransposable element into intron 3 of the Mitf gene that causes the selective deficiency of the melanocyte-specific Mitf isoform, Mitf-M. Here, we show the expression of Mitf-M mRNA in the trunk region of the homozygous Mitf mi-bw ( bw) mouse at embryonic days (E) 11.5 and E12.5, but Mitf-M mRNA is undetectable at E13.5. In addition, using bw mouse that carries the lacZ transgene under the control of a melanoblast-specific promoter, we show that the number of migrating melanoblasts in bw embryos was less than 10% of that in control embryos at E11.5 and E12.5, and melanoblasts disappear by E13.5. The loss of melanoblasts in bw embryos was probably caused by apoptosis. Finally, forced expression of Mitf-M in the cultured neural tube of bw embryos ensured the differentiation of melanoblasts. Therefore, the correct dose of Mitf-M is required for the normal development of melanoblasts. [ABSTRACT FROM AUTHOR]

Many plant species are susceptible to high-temperature (HT) injury during reproductive development. We recently demonstrated that HT represses the expression of YUCCA auxin biosynthesis genes and reduces endogenous auxin in the developing anthers of barley and Arabidopsis. Here, we show that DNA proliferation in mitochondria, chloroplasts and nuclei of developing panicles is inhibited with increasing temperatures in barley. Following DNA proliferation suppression, terminal abnormalities were observed in the organelles of anther wall cells, including mitochondrial swelling and overdevelopment of chloroplasts. Comprehensive transcriptome analyses using both reproductive organs and vegetative tissues showed high and positive pairwise correlations between the expression profiles of auxin-induced genes, DNA replication-related genes and mitochondrial-related genes. In contrast, the expression profiles of auxin-repressed protein genes and photosynthesis-/chloroplast-related genes were negatively correlated with those of the previously mentioned genes. Under HT conditions, the former was repressed and the latter was up-regulated in the developing panicles. Furthermore, application of exogenous auxin promoted the expression of DNA replication-related genes under HT conditions, inducing anther cell proliferation. These suggest that compromised auxin biosynthesis/IAA level under HT condition results in nuclear and organellar DNA proliferation arrest due to co-transcriptional alterations. [ABSTRACT FROM AUTHOR]

The first International Caenorhabditis elegans Experiment (ICE-First) was carried out using a Russian Soyuz spacecraft from April 19–30, 2004. This experiment was apart of the program of the DELTA (Dutch Expedition for Life science Technology and Atmospheric research) mission, and the space agencies that participate in the International Space Station (ISS) program formed international research teams. A Japanese research team that conducted by Japan aerospace Exploration Agency (JAXA) investigated the following aspects of the organism: (1) whether meiotic chromosomal dynamics and apoptosis in the germ cells were normal under microgravity conditions, (2) the effect of the space flight on muscle cell development, and (3) the effect of the space flight on protein aggregation. In this article, we summarize the results of these biochemical and molecular biological analyses. [ABSTRACT FROM AUTHOR]

Roots display hydrotropism in response to moisture gradients, which is thought to be important for controlling their growth orientation, obtaining water, and establishing their stand in the terrestrial environment. However, the molecular mechanism underlying hydrotropism remains unknown. Here, we report that roots of the Arabidopsis mutant mizu-kussei1 (miz1), which are impaired in hydrotropism, show normal gravitropism and elongation growth. The roots of mizl plants showed reduced phototropism and a modified wavy growth response. There were no distinct differences in morphological features and root structure between miz1l and wild-type plants. These results suggest that the pathway inducing hydrotropism is independent of the pathways used in other tropic responses. The phenotype results from a single recessive mutation in MIZ1, which encodes a protein containing a domain (the MIZ domain) that is highly conserved among terrestrial plants such as rice and moss. The MIZ domain was not found in known genomes of organisms such as green algae, red algae, cyanobacteria, or animals. We hypothesize that MIZ1 has evolved to play an important role in adaptation to terrestrial life because hydrotropism could contribute to drought avoidance in higher plants. In addition, a pMIZ1::GUS fusion gene was expressed strongly in columella cells of the root cap but not in the elongation zone, suggesting that MIZ1 functions in the early phase of the hydrotropic response. [ABSTRACT FROM AUTHOR]

Purpose: To investigate positional effects of radiation with an energetic heavy-ion microbeam on germline cells using an experimental model metazoan Caenorhabditis elegans . Materials and methods: The germline cells were irradiated with raster-scanned broad beam or collimated microbeam of 220 MeV 12 C 5+ particles delivered from the azimuthally varying field (AVF) cyclotron, and subsequently observed for cell cycle arrest and apoptosis. Results: Whole-body irradiation with the broad beam at the L4 larval stage arrested germ cell proliferation. When the tip region of the gonad arm was irradiated locally with the microbeam at the L4 stage, the same arrest was observed. When the microbeams were used to irradiate the pachytene region of the gonad arm, at a young gravid stage, radiation-induced apoptosis occurred in the gonad. In contrast, arrest and apoptosis were not induced in the non-irradiated neighboring region or the opposite gonad. Similar results were confirmed in the c-abl-1 (mammalian ortholog of cellular counterpart of Abelson murine leukemia virus) mutant that is hypersensitive to radiation-induced apoptosis. Conclusion: These results indicate that the microbeam irradiation is useful in characterizing tissue-specific, local biological response to radiation in organisms. DNA damage-induced cell cycle arrest and apoptosis were observed in locally irradiated regions, but there was little, if any, ‘bystander effect’ in the nematode. [ABSTRACT FROM AUTHOR]

High-temperature induction of male sterility during floral organogenesis is a critical problem for barley ( Hordeum vulgare L.) crops that the molecular basis is incompletely understood. Gene expression and differentiation of anthers were examined under normal (20°C day/15°C night) and elevated (30°C day/25°C night) temperatures. Serial analysis of gene expression analysis displayed contrasting profiles of gene expression in early panicles between control and high-temperature conditions. Several transcripts dramatically upregulated before development and differentiation of anther wall layers in normal temperatures, including histone H3, H4 and glycine-rich RNA-binding protein genes, were not upregulated at elevated temperatures and typically abundant mRNAs, such as 60S ribosomal protein L27a and glyoxalase I, appeared to be downregulated. Instead, development and differentiation of tapetum cells and pollen mother cells were completely aborted. Failure of transcriptional reactivation with return to normal temperatures increases with duration of elevated temperatures and is strongly correlated with observation of male sterility. Hyper-phosphorylation of the ser-5 residue of the C-terminal domain of the largest subunit of RNA polymerase II (RPB1) was noted to occur under high-temperature conditions. These results indicate that early development and differentiation of barley anthers are very sensitive to high-temperature stress causing major alterations in gene expression. [ABSTRACT FROM AUTHOR]

The RING-H2 finger protein RBX1 (ROC1/HRT1) is a common subunit of SKP1-CDC53/CUL1-F-box (SCF), other cullins and von Hippel-Lindau (VHL) tumour suppressor E3 ubiquitin ligase complexes. RBX1 protein sequences are highly conserved in various species, including yeasts, Drosophila melanogaster, mice and humans. In Saccharo-myces cerevisiae, RBX1 is essential for the G1/S transition. Caenorhabditis elegans RBX1 is strongly expressed in early embryos and in the gonad, including meiotic cells. Depletion of RBX1 by RNA-mediated interference (RNAi) caused pronounced defects in the first meiotic division. Several irregular phenotypes were identified in embryos that escaped from meiotic arrest: defects in mitotic chromosomal condensation and segregation, abnormal chromosome bridges, giant nuclei, abnormal cortical protrusion, multinucleate cells and defects in germ cell proliferation. Moreover, histone H3 phosphorylation at Ser10 and Ser28 was significantly reduced in these embryos. The histone H3 phosphorylation defect of embryos was rescued by the additional depletion of protein phosphatase 1 (GLC7α/β) by RNAi. These results indicate that the RBX1 protein participates in diverse functions relevant to chromosome metabolism and cell cycle control. [ABSTRACT FROM AUTHOR]

During meiotic prophase 1, homologous recombination is accompanied by dynamic chromosomal changes. The Ce-rdh-1/rad-51 gene is the only bacterial recA-like gene in the nematode C. elegans genome. Upon depletion of Ce-rdh-1/rad-51 using the RNA interference method, abnormal ‘kinked’ chromosomes can be observed in mature oocytes at diakinesis, whereas synapsis between homologous chromosomes during the pachytene stage is normal. Following fertilization, Ce-rdh-1/rad-51-depleted embryos die early in embryogenesis, and their nuclei exhibit abnormal chromosome fragments and bridges. From epistasis analyses with Ce-spo-11 defective mutant and ionizing radiation, it is indicated that Ce-rdh-1/rad-51 functions after double-strand break (DSB) formation of meiotic recombination. Under the Ce-chk-2 defective condition, whose meiotic synapsis and meiotic recombination between homologous chromosomes are completely inhibited, the Ce-rdh-1/rad51 is normally expressed in the gonadal cells. Moreover, it seems that exogenous DSBs in the Ce-chk-2 defective nuclei at the pachytene stage can be repaired between sister chromatids in a Ce-rdh-1/rad-51-dependent manner. These results indicate that Ce-rdh-1/rad51 functions after both endogenous and exogenous DSB formation during meiosis, but not as ‘pairing centers’ for meiotic synapsis. [ABSTRACT FROM AUTHOR]

Seedlings of most cucurbitaceous plants develop a peg (protuberance caused by cell outgrowth) on the transition zone between the hypocotyl and root. The peg is necessary for removing the seed coat after germination. In our spaceflight experiments on the STS-95 space shuttle, Discovery, we found that cucumber (Cucumis sativus L.) seedlings grown under microgravity conditions developed two pegs symmetrically at the transition zone. Thus, cucumber seedlings potentially develop two pegs and do not require gravity for peg formation itself, but on the ground the development of one peg is suppressed in response to gravity. This may be considered as negative control of morphogenesis by gravity. [ABSTRACT FROM AUTHOR]

In order to study gene expression in a reproductive organ, we constructed a cDNA library of mature flower buds in Lotus japonicus, and characterized expressed sequence tags (ESTs) of 842 clones randomlyselected. The EST sequences were clustered into 718 non-redundant groups. From BLAST and FASTA search analyses of both protein and DNA databases, 58.5% of the EST groups showed significant sequence similarities to known genes. Several genes encoding these EST clones were identified as pollen-specific genes, such as pectin methylesterase, ascorbate oxidase, and polygalacturonase, and as homologous genes involved in pollen-pistil interaction. Comparison of these EST sequences with those derived from the whole plant of L. japonicus, revealed that 64.8% of EST sequences from the flower buds were not found in EST sequences of the whole plant. Taken together, the EST data from flower buds generated in this study is useful in dissecting gene expression in floral organ of L. japonicus. [ABSTRACT FROM PUBLISHER]

The development of a nonconventional nitrogen fertilizer, which can be fixed in agricultural fields using decentralized renewable energy sources, presents a feasible solution for sustainable on‐site nitrogen fixation and fertilization. This study focuses on plasma‐generated dinitrogen pentoxide (N2O5) as a prospective mediator for the on‐site nitrogen fertilization, allowing nitrogen fertilization directly into culture media. Basal dinitrogen pentoxide fertilization demonstrated almost 100% dinitrogen pentoxide dissolution efficiency as nitrate in a culture medium and nitrogen fertilization effect on plant growth without explicit symptoms of damage. Top‐dressing of dinitrogen pentoxide was also an efficient method for transferring nitrogen into the soil as nitrate, which improved plant growth and suppressed nitrogen deficiency symptoms, while overdose caused adverse effects. [ABSTRACT FROM AUTHOR]