Exploring simple ways to avoid collecting highly 137Cs-contaminated Aralia elata buds for the revival of local wild vegetable cultures.

Collection and cooking of wild vegetables have provided seasonal enjoyments for Japanese local people as provisioning and cultural ecosystem services. However, the Fukushima Daiichi Nuclear Power Plant accident in March 2011 caused extensive radiocesium contamination of wild vegetables. Restrictions on commercial shipments of wild vegetables have been in place for the last 10 years. Some species, including buds of Aralia elata, are currently showing radiocesium concentrations both above and below the Japanese reference level for food (100 Bq/kg), implying that there are factors decreasing and increasing the 137Cs concentration. Here, we evaluated easy-to-measure environmental variables (dose rate at the soil surface, organic soil layer thickness, slope steepness, and presence/absence of decontamination practices) and the 137Cs concentrations of 40 A. elata buds at 38 locations in Fukushima Prefecture to provide helpful information on avoiding collecting highly contaminated buds. The 137Cs concentrations in A. elata buds ranged from 1 to 6,280 Bq/kg fresh weight and increased significantly with increases in the dose rate at the soil surface (0.10-6.50 µSv/h). Meanwhile, the 137Cs concentration in A. elata buds were not reduced by decontamination practices. These findings suggest that measuring the latest dose rate at the soil surface at the base of A. elata plants is a helpful way to avoid collecting buds with higher 137Cs concentrations and aid in the management of species in polluted regions.

Study on the relationship between the dispersal of wild boar (Sus scrofa) and the associated variability of Cesium-137 concentrations in its muscle Post-Fukushima Daiichi Nuclear Power Plant accident.

After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in 2011, the wild boar (Sus scrofa) population within the Fukushima Evacuation Zone (FEZ) increased substantially in size and distribution. This growing population and their potential dispersal from the FEZ, where they are exposed to high levels of radionuclides, into the surrounding landscape underscores the need to better understand boar movement patterns in order to establish policies for managing shipping restrictions for boar meat and develop management strategies. In this study, we quantified the genetic population structure of boar in and around Fukushima prefecture using sequence data of the mitochondrial DNA control region and MIG-seq analysis using 348 boar samples to clarify boar dispersal patterns. Among boar samples, seven Asian haplotypes and one European haplotype were detected. The European haplotype originated from hybridization between domestic pigs and native boar in the evacuation zone after the accident and was detected in 15 samples across a broad geographic area. Our MIG-seq analysis revealed genetic structure of boar was significantly different between boar inhabiting the eastern (including FEZ. i.e., East clade) and western (i.e., West clade) regions in Fukushima prefecture. In addition, we investigated the relationships between boar dispersal and Cesium (Cs)-137 activity concentrations in boar muscle using MIG-seq genetic data in Nihonmatsu city, located in the central-northern region of Fukushima. High Cs-137 activity concentrations, exceeding 1000 Bq/kg, in boar muscle had a significantly high probability of belonging to the East clade within localized regions. Thus, our results provide evidence of the spatial scale of dispersal of individuals or offspring of boar from the FEZ. Results of this research also indicate that dispersal of individuals between areas with different Cs-137 contamination levels is one of the biggest factors contributing to variation in Cs-137 activity concentration in boar muscle within localized regions.

Explaining the variation in 137Cs aggregated transfer factor for wild edible plants as a case study on Koshiabura (Eleutherococcus sciadophylloides) buds.

The aggregated transfer factor (Tag) is commonly used to represent the actual transfer of radiocesium from soil to wild edible plants, but the values have shown substantial variation since the Fukushima nuclear accident. To elucidate the factors causing this variation, we investigated the effects of spatial scale and vertical 137Cs distribution in the soil on the variation of Tag-137Cs values for one of the most severely contaminated wild edible plants, Eleutherococcus sciadophylloides Franch. et Sav. (Koshiabura). The variation in Tag-137Cs values was not reduced by direct measurement of 137Cs deposition in soil samples from the Koshiabura habitat, as a substitute for using spatially averaged airborne survey data at the administrative district scale. The 137Cs activity concentration in Koshiabura buds showed a significant positive correlation with the 137Cs inventories only in the organic horizon of soil from the Koshiabura habitat. The ratio of 137Cs inventories in the organic horizon to the total 137Cs deposition in soil exhibited substantial variation, especially in broad-leaved deciduous forests that Koshiabura primarily inhabits. This variation may be the cause of the wide range of Tag-137Cs values observed in Koshiabura buds when calculated from the total 137Cs deposition in soil.

Monitoring of radioactive cesium in wild boars captured inside the difficult-to-return zone in Fukushima Prefecture over a 5-year period.

Following the Fukushima Daiichi Nuclear Power Plant accident in 2011, tissue samples from wild boar (Sus scrofa) outside the evacuation zone (difficult-to-return zone, DRZ) tended to show high activity concentrations of cesium-137 (137Cs). Understanding the 137Cs dynamics of wild boar populations inside the DRZ is necessary because they affect 137Cs dynamics and wild boar management in areas outside the DRZ. Since few detailed, long-term studies have been conducted inside the DRZ, we measured 137Cs activity concentrations in 221 wild boar muscle samples obtained from wild boar caught inside the DRZ and surrounding areas over a 5-year period. Our results showed that the 137Cs activity concentration in wild boar from inside the DRZ were higher than those in wild boar outside this zone. No significant difference was observed between muscle and soil 137Cs levels, but significant correlations were observed between muscle 137Cs activity concentrations and body length and body weight in the low-activity-concentration season, but not between all seasons and the high-activity-concentration seasons. It is considered that the size effects observed during the low-activity-concentration season may be due to factors related to metabolism and changes in food habit. This is the first long-term survey of 137Cs in wild boar inside the DRZ.

Genetic Population Structure of Wild Boars (Sus scrofa) in Fukushima Prefecture.

We aimed to reveal the dispersal and gene flow of the local wild boar (Sus scrofa) population and find their genetic boundary in Fukushima Prefecture. After the nuclear incident in 2011, the land was considered a difficult-to-return zone, and the increase in the number of wild boars was pronounced. To provide an effective management strategy for the wild boar population, we used multiplexed inter-simple sequence repeat genotyping by sequencing (MIG-seq) and clarified the genetic structure of wild boars. We obtained 328 single-nucleotide polymorphisms from 179 samples. STRUCTURE analysis showed that the most likely number of population cluster was K = 2. Molecular analysis of variance showed significant genetic differences between groups of wild boars inhabiting in the east and west across the Abukuma River. The migration rate from the eastern population to the western population is higher than in the reverse case based on BayesAss analysis. Our study indicates that both the Abukuma River and anthropogenic urbanization along the river may affect the migration of wild boars and the population in western was established mainly by the migration from other neighboring prefectures.

Untangling radiocesium dynamics of forest-stream ecosystems: A review of Fukushima studies in the decade after the accident.

Forest-stream ecosystems are widespread and biodiverse terrestrial landscapes with physical and social connections to downstream human activities. After radiocesium is introduced into these ecosystems, various material flows cause its accumulation or dispersal. We review studies conducted in the decade after the Fukushima nuclear accident to clarify the mechanisms of radiocesium transfer within ecosystems and to downstream areas through biological, hydrological, and geomorphological processes. After its introduction, radiocesium is heavily deposited in the organic soil layer, leading to persistent circulation due to biological activities in soils. Some radiocesium in soils, litter, and organisms is transported to stream ecosystems, forming contamination spots in depositional habitats. While reservoir dams function as effective traps, radiocesium leaching from sediments is a continual phenomenon causing re-contamination downstream. Integration of data regarding radiocesium dynamics and contamination sites, as proposed here, is essential for contamination management in societies depending on nuclear power to address the climate crisis.

Genetic Diversity of Invasive Spartina alterniflora Loisel. (Poaceae) Introduced Unintentionally Into Japan and Its Invasion Pathway.

Among invasive species, aquatic plants pose serious threats to local biodiversity and ecosystem functions. Spartina alterniflora Loisel. (Poaceae), native to the eastern United States, was introduced unintentionally into Japan (Aichi and Kumamoto Prefectures) at around 2010. This invasive species could easily and rapidly spread to estuarine areas of Japan via vigorous trade and transport, making the prediction of its future invasion necessary. Here, the distribution and structure of the genetic variation of S. alterniflora in Japan were examined using chloroplast DNA (cpDNA) and microsatellite genotyping analyses for clarifying its invasion route and process. According to the cpDNA analysis, S. alterniflora populations in Japan had a single haplotype (haplotype C4) that is the most dominant genotype around the Florida Peninsula, the region of its origin, and is also widely found in the introduced populations in the East Asia. Microsatellite analysis also showed a loss of genetic diversity in Japanese S. alterniflora populations (allelic richness (A R) = 1.20-1.39) compared with that in its native region (A R = 4.58-4.59), suggesting a founder effect on S. alterniflora that might have occurred after invasion of the species into Japan. The principal coordinate analysis and The STRUCTURE analysis indicated that no gene mixing among Japanese local populations (Aichi, northern and southern Kumamoto) was observed, indicating that Spartina invasion occurred independently into these regions. Among the three regions, trading between the ports of northern Kumamoto and the U.S. was obviously lower than trading with China. We concluded that invasive S. alterniflora might have independently invaded Japan at different times through an East Asia route, particularly via China (i.e., secondary introduction). Therefore, it is important to strengthen the quarantine control on the importation of commodities, especially of transport vehicles at potential donor spots (i.e., border control/border biosecurity system), and to share information networks on invasive species between each region/port for minimizing further risks of biological species such as Spartina.

Comparison of 0.1 M Stable CsCl and 1 M NH4NO3 as an Extraction Reagent to Evaluate Cs-137 Mobility in Soils.

To evaluate the mobility and bioavailability of 137Cs in soils, we compared the extraction of 137Cs with stable Cs and ammonium solutions from 137Cs-contaminated minerals and soils. The extraction yields of 137Cs with stable Cs were significantly lower than those with ammonium for minerals with frayed edge sites, but such differences were not observed for minerals without frayed edge sites. The amount of 137Cs extracted with stable Cs from soils was lower than, or equal to, that extracted with ammonium. The above results suggest that stable Cs extracted the 137Cs from easily accessible sites. Plant available 137Cs was assessed using Kochia (Bassia scoparia) cultivated in pots of contaminated soils, and compared with soil parameters including extractable 137Cs and K, and radiocesium intercept potential. The 137Cs/K ratio extracted with stable Cs solution was found to be a potential index for evaluation of the easily mobile and bioavailable fraction of 137Cs in soil.

Ozone-Sensitive Arabidopsis Mutants with Deficiencies in Photorespiratory Enzymes.

An ozone-sensitive mutant was isolated from T-DNA-tagged lines of Arabidopsis thaliana. The T-DNA was inserted at a locus on chromosome 3, where two genes encoding glycolate oxidases, GOX1 and GOX2, peroxisomal enzymes involved in photorespiration, reside contiguously. The amounts of the mutant's foliar transcripts for these genes were reduced, and glycolate oxidase activity was approximately 60% of that of the wild-type plants. No difference in growth and appearance was observed between the mutant and the wild-type plants under normal conditions with ambient air under a light intensity of 100 µmol photons m-2 s-1. However, signs of severe damage, such as chlorosis and ion leakage from the tissue, rapidly appeared in mutant leaves in response to ozone treatment at a concentration of 0.2 µl l-1 under a higher light intensity of 350 µmol photons m-2 s-1 that caused no such symptoms in the wild-type plant. The mutant also exhibited sensitivity to sulfur dioxide and long-term high-intensity light. Arabidopsis mutants with deficiencies in other photorespiratory enzymes such as glutamate:glyoxylate aminotransferase and hydroxypyruvate reductase also exhibited ozone sensitivities. Therefore, photorespiration appears to be involved in protection against photooxidative stress caused by ozone and other abiotic factors under high-intensity light.

Effects of environmental radiation on testes and spermatogenesis in wild large Japanese field mice (Apodemus speciosus) from Fukushima.

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident that occurred after the Great East Japan Earthquake in March 2011 released large quantities of radionuclides to the environment. The long-term effects of radioactive cesium (Cs) on biota are of particular concern. We investigated the accumulation of radioactive Cs derived from the FDNPP accident, and chronic effects of environmental radionuclides on male reproduction, in the large Japanese field mouse (Apodemus speciosus). In 2013 and 2014, wild mice were captured at 2 sites in Fukushima Prefecture and at 2 control sites that were distant from Fukushima. Although the median concentrations of (134)Cs and (137)Cs in the mice from Fukushima exceeded 4,000 Bq/kg, there were no significant differences in the apoptotic cell frequencies or the frequencies of morphologically abnormal sperm among the capture sites. Thus, we conclude that radiation did not cause substantial male subfertility in Fukushima during 2013 and 2014, and radionuclide pollution levels in the study sites would not be detrimental to spermatogenesis of the wild mice in Fukushima.

Elevated Ozone Deteriorates Grain Quality of Japonica Rice cv. Koshihikari, Even if it Does Not Cause Yield Reduction.

BACKGROUND: It is becoming clear that ozone affects not only grain yield but also grain quality in rice. However, the biochemical mechanisms responsible for ozone-induced changes in appearance quality or components are poorly understood. We analyzed appearance quality and starch composition in the rice cultivars "Koshihikari" (japonica) and "Kasalath" (indica) grown under elevated ozone conditions. RESULTS: Elevated ozone significantly increased the proportion of immature (mainly chalky) kernels in "Koshihikari" but not in "Kasalath". Scanning electron microscopy of transverse sections of kernels showed that endosperm starch granules of "Koshihikari" ripened under elevated ozone were loosely packed with large spaces and contained irregular rounded granules. Amylose content was increased in "Koshihikari" kernels with ozone exposure, but was unchanged in "Kasalath" kernels. Distribution analysis of amylopectin chain length showed that ozone induces a decrease of long-side chains and alterations of short side-chains in "Koshihikari" kernels. Furthermore, Starch Synthase (SS) IIIa transcript levels in "Koshihikari" caryopses were decreased by elevated ozone. CONCLUSIONS: The japonica cultivar "Koshihikari" showed significant deterioration in appearance quality of kernels caused by abnormal starch accumulation due to exposure to ozone. The alteration patterns of amylose and amylopectin in ozone-exposed rice kernels are similar to those in rice kernels harvested from SSIIIa-deficient mutants. These findings suggest that the increase of chalky kernels in ozone-treated "Koshihikari" is partly attributable to the repressed expression of SSIIIa involved in amylopectin side-chain elongation with ozone exposure. Elevated ozone reduced appearance quality in "Koshihikari" although it did not impair starch properties contributing to the eating quality of cooked rice.

Fixed-route monitoring and a comparative study of the occurrence of herbicide-resistant oilseed rape (Brassica napus L.) along a Japanese roadside.

Previously, we conducted a roadside survey to reveal the occurrence of genetically modified (GM) oilseed rape along a Japanese roadside (Route 51). In this study, we performed successive and thorough fixed-route monitoring in 5 sections along another road (Route 23). Oilseed rape plants were detected on both sides of the road in each section between autumn 2009 and winter 2013, which included 3 flowering seasons. In four sections, more plants were found on the side of the road leading from the Yokkaichi port than on the opposite side. In the fifth section, the presence of clogged drains on the roadside, where juvenile plants concentrated, caused the opposite distribution: oilseed rape predominantly occurred along the inbound lanes (leading to the Yokkaichi port) in 2010 and 2012. Unlike in our previous survey, glyphosate- or glufosinate-resistant oilseed rape plants were abundant (>75% of analyzed plants over 3 years). Moreover, a few individuals bearing both herbicide resistance traits were also detected in some sections. The spillage of imported seeds may explain the occurrence of oilseed rape on the roadside. The abundance of herbicide-resistant oilseed rape plants may reflect the extent of contamination with GM oilseed rape seed within imports.

Ozone-Induced Rice Grain Yield Loss Is Triggered via a Change in Panicle Morphology That Is Controlled by ABERRANT PANICLE ORGANIZATION 1 Gene.

Rice grain yield is predicted to decrease in the future because of an increase in tropospheric ozone concentration. However, the underlying mechanisms are unclear. Here, we investigated the responses to ozone of two rice (Oryza Sativa L.) cultivars, Sasanishiki and Habataki. Sasanishiki showed ozone-induced leaf injury, but no grain yield loss. By contrast, Habataki showed grain yield loss with minimal leaf injury. A QTL associated with grain yield loss caused by ozone was identified in Sasanishiki/Habataki chromosome segment substitution lines and included the ABERRANT PANICLE ORGANIZATION 1 (APO1) gene. The Habataki allele of the APO1 locus in a near-isogenic line also resulted in grain yield loss upon ozone exposure, suggesting APO1 involvement in ozone-induced yield loss. Only a few differences in the APO1 amino acid sequences were detected between the cultivars, but the APO1 transcript level was oppositely regulated by ozone exposure: i.e., it increased in Sasanishiki and decreased in Habataki. Interestingly, the levels of some phytohormones (jasmonic acid, jasmonoyl-L-isoleucine, and abscisic acid) known to be involved in attenuation of ozone-induced leaf injury tended to decrease in Sasanishiki but to increase in Habataki upon ozone exposure. These data indicate that ozone-induced grain yield loss in Habataki is caused by a reduction in the APO1 transcript level through an increase in the levels of phytohormones that reduce leaf damage.

Classification of the spermatogenic cycle, seasonal changes of seminiferous tubule morphology and estimation of the breeding season of the large Japanese field mouse (Apodemus speciosus) in Toyama and Aomori prefectures, Japan.

The large Japanese field mouse, Apodemus speciosus, is a potential indicator of environmental stress, but this function has not been confirmed by histological studies. Since environmental stress affects the reproductive function of mice, we determined the reproductive characteristics of this species at two locations: Toyama (36°35'N, 137°24'E) and Aomori (40°35'N, 140°57'E). Mice were captured during May-November (n=119) and July-November (n=146) at these locations, respectively. We classified the breeding season from the numbers of pregnant females and young, in addition to the spermatogenic cycle and seasonal changes in seminiferous tubule morphology of males. Testicular weight was measured, and seminiferous tubule morphology was examined histologically. Fourteen stages were found in the seminiferous epithelium cycle based on acrosome formation and spermatid head morphology. At both locations, the breeding season peaked from late summer to early autumn and possibly in spring. Spermatogenic activity was classified into 4 periods from June to November: resting around June and October-November; resumptive around July; active around August; and degenerative around September. During the resting period, the seminiferous tubules consisted of Sertoli cells, spermatogonia and spermatocytes. Spermatogenesis began during the resumptive period, and spermatids were observed. During the active period, active spermatogenesis and a broad lumen were observed. During the degenerative period, spermatogenesis ended, and Sertoli cells, spermatogonia, spermatocytes and degenerating exfoliated round spermatids were observed. This study provides scientific information about the testicular histopathological evaluations of the large Japanese field mouse for its use as an index species of environmental pollution.

Alteration of Arabidopsis SLAC1 promoter and its association with natural variation in drought tolerance.

Natural variation for drought tolerance is a major issue in adaptation and geographic distribution of terrestrial plants. Despite the importance, little is known about the genes and molecular mechanisms that determine its naturally occurring diversity. We analyzed the intraspecific drought tolerance variation between 2 accessions of Arabidopsis thaliana, Columbia (Col)-0 and Wassilewskija (Ws)-2. Measurement of weight loss in detached seedlings demonstrated a clear difference between drought-tolerant Col-0 and drought-sensitive Ws-2. They also differed in their stomatal response under drought condition. Using a quantitative genetic approach, we found a significant quantitative locus on chromosome 1. Surveying in the locus, we extrapolated that the SLAC1 gene, which is associated with stomatal closure, was likely responsible for the difference of drought tolerance. Comparison of their nucleotide and amino acid sequences revealed that there were few differences in regions encoding SLAC1 protein but was a large deletion in SLAC1 promoter of Ws-2. Histochemical GUS staining showed that the SLAC1 expressed dominantly in guard cells of Col-0, but did less in guard cells of Ws-2. Quantitative PCR analysis also showed that transcript level of SLAC1 in guard cells was higher in Col-0 than in Ws-2. The SLAC1 transcription analyses indicate low accumulation of SLAC1 in guard cells of Ws-2. When taken together, our results suggest that the low drought tolerance of Ws-2 was associated with the deletion of the promoter region of Ws-2 SLAC1.

¹³7Cs concentrations in foliose lichens within Tsukuba-city as a reflection of radioactive fallout from the Fukushima Dai-ichi Nuclear Power Plant accident.

(137)Cs concentrations in ten species of foliose lichens collected within Tsukuba-city in August 2013 ranged from 1.7 to 35 kBq/kg. The relationships between (137)Cs in two dominant species, Dirinaria applanata and Physcia orientalis, and the air dose rate (µSv/h) at the sampling sites were investigated. (137)Cs in P. orientalis measured about 1 year after the Fukushima nuclear accident was correlated (r(2) = 0.80) more closely with the air dose rate than those measured after about 2 years (r(2) = 0.65), possibly demonstrating its continued value as a biomonitor to reflect ambient fall-out levels. In contrast, those of Dirinaria applanata were not correlated with the air dose rate in either year.

High-throughput capture of nucleotide sequence polymorphisms in three Brassica species (Brassicaceae) using DNA microarrays.

PREMISE OF THE STUDY: To capture molecular markers that are applicable to environmental risk assessment of genetically modified oilseed rape, and to streamline their development, we screened variations in nucleotide sequences of three Brassica species by DNA microarray analysis. METHODS AND RESULTS: Using the Affymetrix GeneChip Arabidopsis ATH1 Genome Array, we monitored gene expression at 22810 loci among the Brassica species and picked out 192 putative polymorphic loci. We sequenced 25 of these and successfully aligned them among all three species. All 25 loci possessed some interspecific and at times intraspecific nucleotide variation. CONCLUSIONS: DNA microarray analysis effectively detected a large number of nucleotide sequence variations among closely related Brassica species. The polymorphic regions will allow the subsequent development of functional gene markers.

The integral membrane protein SEN1 is required for symbiotic nitrogen fixation in Lotus japonicus nodules.

Legume plants establish a symbiotic association with bacteria called rhizobia, resulting in the formation of nitrogen-fixing root nodules. A Lotus japonicus symbiotic mutant, sen1, forms nodules that are infected by rhizobia but that do not fix nitrogen. Here, we report molecular identification of the causal gene, SEN1, by map-based cloning. The SEN1 gene encodes an integral membrane protein homologous to Glycine max nodulin-21, and also to CCC1, a vacuolar iron/manganese transporter of Saccharomyces cerevisiae, and VIT1, a vacuolar iron transporter of Arabidopsis thaliana. Expression of the SEN1 gene was detected exclusively in nodule-infected cells and increased during nodule development. Nif gene expression as well as the presence of nitrogenase proteins was detected in rhizobia from sen1 nodules, although the levels of expression were low compared with those from wild-type nodules. Microscopic observations revealed that symbiosome and/or bacteroid differentiation are impaired in the sen1 nodules even at a very early stage of nodule development. Phylogenetic analysis indicated that SEN1 belongs to a protein clade specific to legumes. These results indicate that SEN1 is essential for nitrogen fixation activity and symbiosome/bacteroid differentiation in legume nodules.

Seeds of a possible natural hybrid between herbicide-resistant Brassica napus and Brassica rapa detected on a riverbank in Japan.

Transgenic herbicide-resistant varieties of Brassica napus, or oilseed rape, from which canola oil is obtained, are imported into Japan, where this plant is not commercially cultivated to a large extent. This study aimed to examine the distribution of herbicide-resistant B. napus and transgene flow to escaped populations of its closely related species, B. rapa and B. juncea. Samples were collected from 12 areas near major ports through which oilseed rape imports into Japan passed--Kashima, Chiba, Yokohama, Shimizu, Nagoya, Yokkaichi, Sakai-Senboku, Kobe, Uno, Mizushima, Kita-Kyushu, and Hakata--and the presence of glyphosate- and/or glufosinate-resistant B. napus was confirmed in all areas except Yokohama, Sakai-Senboku, Uno, and Kita-Kyushu. The Yokkaichi area was the focus because several herbicide-resistant B. napus plants were detected not only on the roadside where oilseed rape spilled during transportation but also on the riverbanks, where escaped populations of B. rapa and B. juncea grew. Samples of B. napus that were tolerant to both herbicides were detected in four continuous years (2005-2008) in this area, suggesting the possibility of intraspecific transgene flow within the escaped B. napus populations. Moreover, in 2008, seeds of a possible natural hybrid between herbicide-tolerant B. napus (2n = 38) and B. rapa (2n = 20) were detected; some seedlings derived from the seeds collected at a Yokkaichi site showed glyphosate resistance and had 2n = 29 chromosomes. This observation strongly suggests the occurrence of hybridization between herbicide-resistant B. napus and escaped B. rapa and the probability of introgression of a herbicide-resistance gene into related escaped species.

Expression and functions of myo-inositol monophosphatase family genes in seed development of Arabidopsis.

Myo-inositol monophosphatase (IMP) catalyzes the dephosphorylation of myo-inositol 3-phosphate in the last step of myo-inositol biosynthesis. IMP is also important in phosphate metabolism and is required for the biosynthesis of cell wall polysaccharides, phytic acid, and phosphatidylinositol. In Arabidopsis, IMP is encoded by VTC4. There are, however, two additional IMP candidate genes, IMPL1 and IMPL2, which have not yet been elucidated. In our genetic studies of Arabidopsis IMP genes, only the loss-of-function mutant impl2 showed embryonic lethality at the globular stage. All IMP genes were expressed in a similar manner both in the vegetative and reproductive organs. In developing seeds, expression of IMP genes was not coupled with the expression of the genes encoding myo-inositol phosphate synthases, which supply the substrate for IMPs in the de novo synthesis pathway. Instead, expression of IMP genes was correlated with expression of the gene for myo-inositol polyphosphate 1-phosphatase (SAL1), which is involved in the myo-inositol salvage pathway, suggesting a possible salvage pathway role in seed development. Moreover, the partial rescue of the impl2 phenotype by histidine application implies that IMPL2 is also involved in histidine biosynthesis during embryo development.