Heterotic growth of hybrids of Arabidopsis thaliana is enhanced by elevated atmospheric CO2.

PREMISE: With the global atmospheric CO2 concentration on the rise, developing crops that can thrive in elevated CO2 has become paramount. We investigated the potential of hybridization as a strategy for creating crops with improved growth in predicted elevated atmospheric CO2. METHODS: We grew parent accessions and their F1 hybrids of Arabidopsis thaliana in ambient and elevated atmospheric CO2 and analyzed numerous growth traits to assess their productivity and underlying mechanisms. RESULTS: The heterotic increase in total dry mass, relative growth rate and leaf net assimilation rate was significantly greater in elevated CO2 than in ambient CO2. The CO2 response of net assimilation rate was positively correlated with the CO2 response of leaf nitrogen productivity and with that of leaf traits such as leaf size and thickness, suggesting that hybridization-induced changes in leaf traits greatly affected the improved performance in elevated CO2. CONCLUSIONS: Vegetative growth of hybrids seems to be enhanced in elevated CO2 due to improved photosynthetic nitrogen-use efficiency compared with parents. The results suggest that hybrid crops should be well-suited for future conditions, but hybrid weeds may also be more competitive.

Whole-plant growth and N utilization in transgenic rice plants with increased or decreased Rubisco content under different CO2 partial pressures.

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) strongly limits photosynthesis at lower CO2 concentration [CO2] whereas [corrected] Rubisco limitation is cancelled by elevated [CO2]. Therefore, increase or reduction in Rubisco content by transformation with a sense or an antisense RBCS construct are expected to alter the biomass production under different CO2 levels. RBCS-sense (125% Rubisco of wild-type) and -antisense (35% Rubisco of wild-type) rice (Oryza sativa L.) plants were grown for 63 days at three different CO2 levels: low [CO2] (28 Pa), normal [CO2] (40 Pa) and elevated [CO2] (120 Pa). The biomass of RBCS-sense plants was 32% and 15% greater at low [CO2] and normal [CO2] than that of the wild-type plants, respectively, but did not differ at elevated [CO2]. Conversely, the biomass of RBCS-antisense plants was the smallest at low [CO2]. Thus, overproduction of Rubisco was effective for biomass production at low [CO2]. Greater biomass production at low [CO2] in RBCS-sense plants was caused by an increase in the net assimilation rate, and associated with an increase in the amount of N uptake. Furthermore, Rubisco overproduction in RBCS-sense plants was also promoted at low [CO2]. Although it seems that low [CO2]-growth additionally stimulates the effect of RBCS overexpression, such a phenomenon observed at low [CO2] was mediated through an increase in total leaf N content. Thus, the dependence of the growth improvement in RBCS-sense rice on growth [CO2] was closely related to the degree of Rubisco overproduction which was accompanied not only by leaf N content but also by whole plant N content.

Visualization of flavonol distribution in the abaxial epidermis of onion scales via detection of its autofluorescence in the absence of chemical processes.

We visualized flavonol distribution in the abaxial epidermis of onion scales without chemical processes via detection of blue-light-induced green autofluorescence. Our visualizing results indicated an unequal intercellular distribution of flavonols among epidermal cells causing a patch distribution in the epidermis, and indicated that flavonol accumulation in ultraviolet irradiated-onion scales was in uniformity with epidermal cells, probably to compensate for their stress-hypersensitiveness.

Parasympathetic vasodilator fibers in rat digastric muscle.

The present study examined whether parasympathetic vasodilator fibers exist in rat jaw-opening muscles such as the digastric muscle. The mental nerve was stimulated to activate the parasympathetic vasodilator nerve in the digastric muscle. Electrical stimulation of the mental nerve elicited intensity- and frequency-dependent increases of blood flow in this muscle. These increases were markedly reduced by hexamethonium in dose- and time-dependent manners, but pretreatment with phentolamine or propranolol had no effect. Pretreatment with atropine also attenuated the increase in blood flow in digastric muscle. When retrograde fluorogold was injected into the digastric muscle, labeled neurons were observed in the otic ganglion only on the ipsilateral side, but not in the pterygopalatine ganglion of either side. These results indicate that parasympathetic vasodilator fibers originate from cell bodies in the otic ganglion in rat digastric muscle.

Unusual sonographic appearance of synovial sarcoma of the anterior abdominal wall.

We report a case of synovial sarcoma in a 58-year-old woman arising from the anterior abdominal wall. Sonography demonstrated a large mass with an unusual complex "honeycomb" echotexture. Doppler imaging displayed increased vascularity in the solid parts of the tumor.

Mandibular residual ridge shape and the masticatory ability in complete denture wearers.

PURPOSE: The purpose of this study was to investigate the influence of mandibular residual ridge shape on the masticatory ability in complete denture wearers. METHODS: The subject group consisted of 199 complete denture wearers. The mandibular residual ridge of each subject was evaluated using a replica of the ridge which was obtained with heavy-body silicone impression material. The basal area of each replica was measured with a digitizer. The volume and the height of each replica were also calculated. The masticatory ability of each subject was evaluated using a-25-item food intake questionnaire method by authors. The masticatory score of each subject was calculated to represent the masticatory ability. Furthermore, all subjects were divided into three groups (S, M, L group) according to the value of the basal area. RESULTS: There were statistically significant correlations between the basal area of the residual ridge and the masticatory score (r = 0.366, p < 0.01), and also the volume of the residual ridge and the masticatory score (r = 0.314, p < 0.01). The basal area of the residual ridge, the volume of the residual ridge, and the masticatory score of the L group (29 persons) were statistically larger than those of the M group (136 persons) and the S group (34 persons) (p < 0.05), and those values in the M group were statistically larger than those of the S group (p < 0.05). CONCLUSION: It was confirmed that the basal area of denture foundation of the mandible had an influence on the masticatory ability in complete denture wearers.

Gene expression and sensitivity in response to copper stress in rice leaves.

Gene expression in response to Cu stress in rice leaves was quantified using DNA microarray (Agilent 22K Rice Oligo Microarray) and real-time PCR technology. Rice plants were grown in hydroponic solutions containing 0.3 (control), 10, 45, or 130 microM of CuCl(2), and Cu accumulation and photosynthesis inhibition were observed in leaves within 1 d of the start of treatment. Microarray analysis flagged 305 Cu-responsive genes, and their expression profile showed that a large proportion of general and defence stress response genes are up-regulated under excess Cu conditions, whereas photosynthesis and transport-related genes are down-regulated. The Cu sensitivity of each Cu-responsive gene was estimated by the median effective concentration value (EC50) and the range of fold-changes (F) under the highest (130 microM) Cu conditions (|log(2)F|(130)). Our results indicate that defence-related genes involved in phytoalexin and lignin biosynthesis were the most sensitive to Cu, and that plant management of abiotic and pathogen stresses has overlapping components, possibly including signal transduction.

Evidence for parasympathetic vasodilator fibres in the rat masseter muscle.

The present study was designed to examine (1) whether there are vasodilator fibres in the masseter muscle, and (2) if there are, to establish the neural pathways mediating these responses in urethane-anaesthetized rats. Electrical stimulation of the central cut end of the lingual nerve (LN) elicited intensity- and frequency-dependent increases of the blood flow in the masseter muscle (MBF) and lower lip (LBF). Increases in both the MBF and LBF evoked by the LN stimulation were reduced by hexamethonium in a dose-dependent manner (1-10 mg kg(-1)). Pretreatment with phentolamine or propranolol at a dose of 100 microg kg(-1) had no effect on the increases in either MBF or LBF evoked by LN stimulation. Pretreatment with atropine (100 microg kg(-1)) significantly reduced the MBF increase induced by LN stimulation, but not that in the LBF. The sectioning of the superior cervical sympathetic trunk did not affect the responses. MBF increases occurred with electrical stimulation of the trigeminal ganglion, and these increases were significantly reduced by the administration of hexamethonium and atropine. Lidocaine microinjection into the trigeminal spinal nucleus or salivatory nuclei caused a significant attenuation of the LN-induced MBF increases. When wheat germ agglutinin-horseradish peroxidase (WGA-HRP) was injected into the masseter muscle, labelled neurones were abundantly observed in the otic ganglion. The present study indicates that there are parasympathetic cholinergic and noncholinergic vasodilator fibres originating from cell bodies in the otic ganglion in the rat masseter muscle. The MBF increase evoked by activation of the parasympathetic fibres occurred via the trigeminal mediated reflex, suggesting that the novel parasympathetic vasodilator response may play an important role in the regulation of the haemodynamics of jaw muscles.

Differences between maize and rice in N-use efficiency for photosynthesis and protein allocation.

The N-use efficiency for photosynthesis was higher in a C(4) plant, maize, than in a C(3) plant, rice, including rbcS antisense rice with optimal ribulose-1,5-bisphosphate carboxylase (Rubisco) content for CO(2)-saturated photosynthesis, even when photosynthesis was measured under saturating CO(2) conditions. The N cost for the C(4) cycle enzymes in maize was not large, and the lower amount of Rubisco allowed a greater N investment in the thylakoid components. This greater content of the thylakoid components as well as the CO(2) concentrating mechanism may support higher N-use efficiency for photosynthesis in maize.