High yielding ability of a large-grain rice cultivar, Akita 63.

To increase the yield potential while limiting the environmental impact of N management practices is an important issue in rice cultivation. The large-grain rice cultivar Akita 63 showed higher N-use efficiency for grain production. To elucidate this, we analyzed yield characteristics of Akita 63 in comparison with those of a maternal cultivar, Oochikara with a large grain, a paternal cultivar, Akita 39 with a normal grain, and a Japanese leading cultivar, Akitakomachi. The yields of Akita 63 were 20% higher than those of Oochikara and Akita 39, and 50% higher than those of Akitakomachi for the same N application. Akita 63 showed superior N uptake capacity. Whereas a trade-off between single grain weight and grain number was found for Oochikara, Akita 63 did not show such a relationship. The success in Akita 63 breeding was due to overcoming such a trade-off. Akita 63 had the large-grain alleles of GS3 and qSW5. Thus, an enlargement of grain size can have a great impact on an increase in yield with improved N-use efficiency. However, an enlargement of sink capacity led to source limitation. Thus, both sink and source improvements are essential for a further increase in the yield of today's high-yielding cultivars.

The urea transporter DUR3 contributes to rice production under nitrogen-deficient and field conditions.

Nitrogen is one of the most important elements for plant growth, and urea is one of the most frequently used nitrogen fertilizers worldwide. Besides the exogenously-supplied urea to the soil, urea is endogenously synthesized during secondary nitrogen metabolism. Here, we investigated the contribution of a urea transporter, DUR3, to rice production using a reverse genetic approach combined with localization studies. Tos17 insertion lines for DUR3 showed a 50% yield reduction in hydroponic culture, and a 26.2% yield reduction in a paddy field, because of decreased grain filling. Because shoot biomass production and shoot total N was not reduced, insertion lines were disordered not only in nitrogen acquisition but also in nitrogen allocation. During seed development, DUR3 insertion lines accumulated nitrogen in leaves and could not sufficiently develop their panicles, although shoot and root dry weights were not significantly different from the wild-type. The urea concentration in old leaf harvested from DUR3 insertion lines was lower than that in wild-type. DUR3 promoter-dependent ß-glucuronidase (GUS) activity was localized in vascular tissue and the midribs of old leaves. These results indicate that DUR3 contributes to nitrogen translocation and rice yield under nitrogen-deficient and field conditions.

Collaborative environmental DNA sampling from petal surfaces of flowering cherry Cerasus × yedoensis 'Somei-yoshino' across the Japanese archipelago.

Recent studies have shown that environmental DNA is found almost everywhere. Flower petal surfaces are an attractive tissue to use for investigation of the dispersal of environmental DNA in nature as they are isolated from the external environment until the bud opens and only then can the petal surface accumulate environmental DNA. Here, we performed a crowdsourced experiment, the "Ohanami Project", to obtain environmental DNA samples from petal surfaces of Cerasus × yedoensis 'Somei-yoshino' across the Japanese archipelago during spring 2015. C. × yedoensis is the most popular garden cherry species in Japan and clones of this cultivar bloom simultaneously every spring. Data collection spanned almost every prefecture and totaled 577 DNA samples from 149 collaborators. Preliminary amplicon-sequencing analysis showed the rapid attachment of environmental DNA onto the petal surfaces. Notably, we found DNA of other common plant species in samples obtained from a wide distribution; this DNA likely originated from the pollen of the Japanese cedar. Our analysis supports our belief that petal surfaces after blossoming are a promising target to reveal the dynamics of environmental DNA in nature. The success of our experiment also shows that crowdsourced environmental DNA analyses have considerable value in ecological studies.

A Small Decrease in Rubisco Content by Individual Suppression of RBCS Genes Leads to Improvement of Photosynthesis and Greater Biomass Production in Rice Under Conditions of Elevated CO2.

Rubisco limits photosynthesis at low CO2 concentrations ([CO2]), but does not limit it at elevated [CO2]. This means that the amount of Rubisco is excessive for photosynthesis at elevated [CO2]. Therefore, we examined whether a small decrease in Rubisco content by individual suppression of the RBCS multigene family leads to increases in photosynthesis and biomass production at elevated [CO2] in rice (Oryza sativa L.). Our previous studies indicated that the individual suppression of RBCS decreased Rubisco content in rice by 10-25%. Three lines of BC2F2 progeny were selected from transgenic plants with individual suppression of OsRBCS2, 3 and 5. Rubisco content in the selected lines was 71-90% that of wild-type plants. These three transgenic lines showed lower rates of CO2 assimilation at low [CO2] (28 Pa) but higher rates of CO2 assimilation at elevated [CO2] (120 Pa). Similarly, the biomass production and relative growth rate (RGR) of the two lines were also smaller at low [CO2] but greater than that of wild-type plants at elevated [CO2]. This greater RGR was caused by the higher net assimilation rate (NAR). When the nitrogen use efficiency (NUE) for the NAR was estimated by dividing the NAR by whole-plant leaf N content, the NUE for NAR at elevated [CO2] was higher in these two lines. Thus, a small decrease in Rubisco content leads to improvements of photosynthesis and greater biomass production in rice under conditions of elevated CO2.

Contributions of two cytosolic glutamine synthetase isozymes to ammonium assimilation in Arabidopsis roots.

Glutamine synthetase (GS) catalyzes a reaction that incorporates ammonium into glutamate and yields glutamine in the cytosol and chloroplasts. Although the enzymatic characteristics of the GS1 isozymes are well known, their physiological functions in ammonium assimilation and regulation in roots remain unclear. In this study we show evidence that two cytosolic GS1 isozymes (GLN1;2 and GLN1;3) contribute to ammonium assimilation in Arabidopsis roots. Arabidopsis T-DNA insertion lines for GLN1;2 and GLN1;3 (i.e. gln1;2 and gln1;3 single-mutants), the gln1;2:gln1;3 double-mutant, and the wild-type accession (Col-0) were grown in hydroponic culture with variable concentrations of ammonium to compare their growth, and their content of nitrogen, carbon, ammonium, and amino acids. GLN1;2 and GLN1;3 promoter-dependent green fluorescent protein was observed under conditions with or without ammonium supply. Loss of GLN1;2 caused significant suppression of plant growth and glutamine biosynthesis under ammonium-replete conditions. In contrast, loss of GLN1;3 caused slight defects in growth and Gln biosynthesis that were only visible based on a comparison of the gln1;2 single- and gln1;2:gln1;3 double-mutants. GLN1;2, being the most abundantly expressed GS1 isozyme, markedly increased following ammonium supply and its promoter activity was localized at the cortex and epidermis, while GLN1;3 showed only low expression at the pericycle, suggesting their different physiological contributions to ammonium assimilation in roots. The GLN1;2 promoter-deletion analysis identified regulatory sequences required for controlling ammonium-responsive gene expression of GLN1;2 in Arabidopsis roots. These results shed light on GLN1 isozyme-specific regulatory mechanisms in Arabidopsis that allow adaptation to an ammonium-replete environment.

Mitochondrial Disease as a Cause of Neonatal Hemophagocytic Lymphohistiocytosis.

Diagnosis of mitochondrial respiratory chain disorder (MRCD) is often difficult. Its pathogenesis is still unclear. We diagnosed MRCD by measuring the activity of the mitochondrial respiratory chain enzyme, and the patient also had hemophagocytic lymphohistiocytosis (HLH). A preterm female infant was born at 34 weeks of gestation. On day 6, HLH was revealed by bone marrow aspiration. She died on day 10 due to uncontrollable HLH. An autopsy was performed, and we measured the activity of the mitochondrial respiratory chain enzyme in the liver, muscle, and heart. The activity of complex I was decreased in all tissues. As we could not prove another origin of the HLH, she was diagnosed as having HLH caused by MRCD. It is useful to measure the activity of the mitochondrial respiratory chain enzyme for diagnosing MRCD. MRCD, which has a severe clinical course, may be related to HLH.

Growth Properties and Biomass Production in the Hybrid C4 Crop Sorghum bicolor.

Hybrid vigor (heterosis) has been used as a breeding technique for crop improvement to achieve enhanced biomass production, but the physiological mechanisms underlying heterosis remain poorly understood. In this study, to find a clue to the enhancement of biomass production by heterosis, we systemically evaluated the effect of heterosis on the growth rate and photosynthetic efficiency in sorghum hybrid [Sorghum bicolor (L.) Moench cv. Tentaka] and its parental lines (restorer line and maintainer line). The final biomass of Tentaka was 10-14 times greater than that of the parental lines grown in an experimental field, but the relative growth rate during the vegetative growth stage did not differ. Tentaka exhibited a relatively enlarged leaf area with lower leaf nitrogen content per leaf area (Narea). When the plants were grown hydroponically at different N levels, daily CO2 assimilation per leaf area (A) increased with Narea, and the ratio of A to Narea (N-use efficiency) was higher in the plants grown at low N levels but not different between Tentaka and the parental lines. The relationships between the CO2 assimilation rate, the amounts of photosynthetic enzymes, including ribulose-1,5-bisphosphate carboxylase/oxygenase, phosphoenolpyruvate carboxylase and pyruvate phosphate dikinase, Chl and Narea did not differ between Tentaka and the parental lines. Thus, Tentaka tended to exhibit enlargement of leaf area with lower N content, leading to a higher N-use efficiency for CO2 assimilation, but the photosynthetic properties did not differ. The greater biomass in Tentaka was mainly due to the prolonged vegetative growth period.

Autophagy supports biomass production and nitrogen use efficiency at the vegetative stage in rice.

Much of the nitrogen in leaves is distributed to chloroplasts, mainly in photosynthetic proteins. During leaf senescence, chloroplastic proteins, including Rubisco, are rapidly degraded, and the released nitrogen is remobilized and reused in newly developing tissues. Autophagy facilitates the degradation of intracellular components for nutrient recycling in all eukaryotes, and recent studies have revealed critical roles for autophagy in Rubisco degradation and nitrogen remobilization into seeds in Arabidopsis (Arabidopsis thaliana). Here, we examined the function of autophagy in vegetative growth and nitrogen usage in a cereal plant, rice (Oryza sativa). An autophagy-disrupted rice mutant, Osatg7-1, showed reduced biomass production and nitrogen use efficiency compared with the wild type. While Osatg7-1 showed early visible leaf senescence, the nitrogen concentration remained high in the senescent leaves. (15)N pulse chase analysis revealed suppression of nitrogen remobilization during leaf senescence in Osatg7-1. Accordingly, the reduction of nitrogen available for newly developing tissues in Osatg7-1 likely led its reduced leaf area and tillers. The limited leaf growth in Osatg7-1 decreased the photosynthetic capacity of the plant. Much of the nitrogen remaining in senescent leaves of Osatg7-1 was in soluble proteins, and the Rubisco concentration in senescing leaves of Osatg7-1 was about 2.5 times higher than in the wild type. Transmission electron micrographs showed a cytosolic fraction rich with organelles in senescent leaves of Osatg7-1. Our results suggest that autophagy contributes to efficient nitrogen remobilization at the whole-plant level by facilitating protein degradation for nitrogen recycling in senescent leaves.

Influence of surgical intervention on neurodevelopmental outcome in infants with focal intestinal perforation.

BACKGROUND: Intestinal perforation is known to correlate with neurodevelopmental outcome in very low-birthweight (VLBW) infants, and its two major causes are necrotizing enterocolitis (NEC) and focal intestinal perforation (FIP). Infants with FIP are reported to have better neurodevelopmental outcome than infants with NEC, but outcome has not been compared with that in infants without diseases that require surgery. The aim of this study was to compare neurodevelopmental outcomes between FIP survivors and infants without diseases that require surgery. METHODS: Records of VLBW infants with FIP and infants without surgical diseases were retrospectively analyzed. Neurodevelopmental outcome was compared between eight infants with FIP and 24 case-matched control infants without surgical diseases using the Kyoto Scale of Psychological Development. Control group members were individually matched with FIP survivors for sex, gestational age, birthweight, and intraventricular hemorrhage (IVH) grade. Those with an episode of sepsis or severe IVH (grade 3-4) that occurred irrespective of FIP were excluded. RESULTS: Three FIP survivors and 12 infants without surgical diseases were classified as neurodevelopmentally normal (37.5% vs 50%, P = 0.69) at a corrected age of 18 months-3 years. All neurodevelopmentally normal FIP survivors were born at a gestational age ≥ 26 weeks. CONCLUSION: Excluding the influence of sepsis or severe IVH, no significant difference was found in neurodevelopmental outcome between FIP survivors and infants without surgical diseases. None of the FIP infants born before 26 weeks of gestation, however, had normal neurodevelopment, suggesting that longer gestation might be needed to overcome the stress associated with FIP.

Asparagine synthetase1, but not asparagine synthetase2, is responsible for the biosynthesis of asparagine following the supply of ammonium to rice roots.

Asparagine is synthesized from glutamine by the reaction of asparagine synthetase (AS) and is the major nitrogen form in both xylem and phloem sap in rice (Oryza sativa L.). There are two genes encoding AS, OsAS1 and OsAS2, in rice, but the functions of individual AS isoenzymes are largely unknown. Cell type- and NH4(+)-inducible expression of OsAS1 as well as analyses of knockout mutants were carried out in this study to characterize AS1. OsAS1 was mainly expressed in the roots, with in situ hybridization showing that the corresponding mRNA was specifically accumulated in the three cell layers of the root surface (epidermis, exodermis and sclerenchyma) in an NH4(+)-dependent manner. Conversely, OsAS2 mRNA was abundant in leaf blades and sheathes of rice. Although OsAS2 mRNA was detectable in the roots, its content decreased when NH4(+) was supplied. Retrotransposon-mediated knockout mutants lacking AS1 showed slight stimulation of shoot length and slight reduction in root length at the seedling stage. On the other hand, the mutation caused an approximately 80-90% reduction in free asparagine content in both roots and xylem sap. These results suggest that AS1 is responsible for the synthesis of asparagine in rice roots following the supply of NH4(+). Characteristics of the NH4(+)-dependent increase and the root surface cell-specific expression of OsAS1 gene are very similar to our previous results on cytosolic glutamine synthetase1;2 and NADH-glutamate synthase1 in rice roots. Thus, AS1 is apparently coupled with the primary assimilation of NH4(+) in rice roots.

Lack of cytosolic glutamine synthetase1;2 in vascular tissues of axillary buds causes severe reduction in their outgrowth and disorder of metabolic balance in rice seedlings.

The development and elongation of active tillers in rice was severely reduced by a lack of cytosolic glutamine synthetase1;2 (GS1;2), and, to a lesser extent, lack of NADH-glutamate synthase1 in knockout mutants. In situ hybridization using the basal part of wild-type seedlings clearly showed that expression of OsGS1;2 was detected in the phloem companion cells of the nodal vascular anastomoses and large vascular bundles of axillary buds. Accumulation of lignin, visualized using phloroglucin HCl, was also observed in these tissues. The lack of GS1;2 resulted in reduced accumulation of lignin. Re-introduction into the mutants of OsGS1;2 cDNA under the control of its own promoter successfully restored the outgrowth of tillers and lignin deposition to wild-type levels. Transcriptomic analysis using a 5 mm basal region of rice shoots showed that the GS1;2 mutants accumulated reduced amounts of mRNAs for carbon and nitrogen metabolism, including C1 unit transfer in lignin synthesis. Although a high content of strigolactone in rice roots is known to reduce active tiller number, the reduction of outgrowth of axillary buds observed in the GS1;2 mutants was independent of the level of strigolactone. Thus metabolic disorder caused by the lack of GS1;2 resulted in a severe reduction in the outgrowth of axillary buds and lignin deposition.

Metabolome analysis of photosynthesis and the related primary metabolites in the leaves of transgenic rice plants with increased or decreased Rubisco content.

Because the comprehensive effects on metabolism by genetic manipulation of leaf Rubisco content are unknown, metabolome analysis was carried out on transgenic rice plants with increased or decreased Rubisco content using the capillary electrophoresis-time-of-flight mass spectrometry (CE-TOFMS) technique. In RBCS-sense plants, an increase in Rubisco content did not improve light-saturated photosynthesis. Glyceraldehyde 3-phosphate and sedoheputulose 7-phosphate levels increased, but ribulose bisphosphate (RuBP), ATP and ADP levels were not affected. It is considered from these results that RuBP regeneration independent of ATP supply became a bottleneck for photosynthesis. In RBCS-antisense plants, a decline in Rubisco content decreased photosynthesis with a substantial accumulation of RuBP. ATP and ADP levels also increased and were associated with increases in the diphosphate and triphosphate compounds of other nucleosides. These results imply that a decline in Rubisco content slowed down the Calvin cycle and that the resultant excess energy of ATP was transferred to other nucleoside diphosphates and triphosphates. The levels of amino acids tended to decline in RBCS-sense plants and increase in RBCS-antisense plants, probably reflecting the demand for Rubisco synthesis. Starch and carbohydrate levels decreased only in RBCS-antisense plants. Thus, genetic manipulation of Rubisco contents widely affected C and N metabolism in rice.

Effect of individual suppression of RBCS multigene family on Rubisco contents in rice leaves.

In higher plants, a small subunit of Rubisco is encoded for by an RBCS multigene family in the nuclear genome. However, it is unknown how each multigene member contributes to the accumulation of Rubisco holoenzyme. Here, four RBCS genes that are highly expressed in leaf blaedes of rice (Oryza sativa L.) were individually suppressed by RNAi, and the effects on leaf Rubisco content were examined at seedling, vegetative and reproductive stages. Rubisco contents in each transgenic line declined irrespective of growth stage, and the ratios of Rubisco-N to total N were 66-96% of wild-type levels. The mRNA levels of the suppressed RBCS genes declined significantly, whereas those of the unsuppressed ones did not change drastically. These results indicate that four RBCS genes all contribute to accumulation of Rubisco holoenzyme irrespective of growth stage and that suppression of one RBCS gene is not fully compensated by other RBCS genes. Additionally, the mRNA levels of the large subunit of Rubisco showed a change similar to that of total RBCS mRNA level irrespective of genotype and growth stage. These results suggest that gene expression of RBCS and RBCL is regulated in a coordinated manner at the transcript level in rice.

A Neonatal Case of Autosomal Dominant Hypoparathyroidism without Mutation of the CASR Gene.

We experienced a case of familial hypoparathyroidism with an autosomal dominant pattern of transmission and performed molecular analysis of the calcium-sensing receptor (CASR) gene. The patient was a female neonate, born by cesarean section at term because of breech presentation. Her mother had been diagnosed with idiopathic hypoparathyroidism at the age of 9 yr and had been receiving vitamin D treatment since then. At birth, the patient's serum calcium concentration was 8.4 mg/dl, but it fell to 4.0 mg/dl on the fifth day after birth. Furthermore, her serum intact PTH level was inappropriately low, while hyperphosphatemia and hypomagnesemia were found. She was diagnosed with familial hypoparathyroidism, and was immediately started on oral administration of 1α(OH)D3 (0.1 µg/kg/day) and continuous intravenous infusion of 8.5% calcium gluconate. Additionally, trichlormethiazide was administered because of elevated urinary calcium/creatinine (Ca/Cr) ratio. Her serum calcium concentration gradually improved thereafter. In this case, autosomal dominant hypocalcemia (ADH) due to abnormality in the CASR gene was clinically suspected, but DNA sequencing analysis revealed no mutation of the CASR gene in either the patient or her mother. This result suggests that the patient's hypoparathyroidism may have been caused by abnormality in a gene other than CASR.

Successful intrauterine therapy for fetal goitrous hypothyroidism during late gestation.

We experienced a case of fetal goitrous hypothyroidism in an infant delivered by a 33-year-old woman receiving 300 mg/day of propylthiouracil (PTU) for hyperthyroidism due to Graves' disease. A large fetal goiter (maximum diameter, 60 mm) was detected by magnetic resonance imaging (MRI) at 36 weeks of gestation. Initial fetal blood sampling revealed hypothyroidism with a serum thyroid-stimulating hormone (TSH) of 99 microIU/mL, free triiodothyronine (T(3)) of 1.97 pg/mL, and free thyroxine (T(4)) of 0.29 ng/dL. Consequently, a diagnosis of fetal goitrous hypothyroidism due to transplacental passage of maternal PTU was made. To reduce the risk of perinatal complications, 300 microg of levothyroxine sodium (L-T(4)) was administered into the maternal amniotic fluid twice between 37 and 38 weeks of gestation. Subsequent fetal MRI showed that the size of goiter had decreased. At 38 weeks and 5 days of gestation, a 3042-g male infant was born by cesarean section. There were no severe complications at delivery, although mild tachypnea was observed and the infant's thyroid gland was slightly enlarged. He was treated with L-T(4) for two weeks. At present, his growth and neurological development are normal. This case indicates that intrauterine therapy by the intraamniotic administration of L-T(4) can be effective in treating fetal goitrous hypothyroidism even during late gestation.