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Background Aortic dissection (AD) is an acute critical disease of the cardiovascular system characterized by high mortality and morbidity. According to reports, immune cell infiltration is associated to AD. However, the intrinsic molecular mechanisms underlying the pathogenesis of AD still need to be clarified. Methods Four datasets (GSE52093, GSE98770, GSE153434 and GSE190635) were download through the Gene Expression Omnibus (GEO). Differentially expressed genes (DEGs) of each dataset were screened by robust rank aggregation (RRA) algorithms. Gene ontology (GO) functional enrichment analysis and Kyto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed to DEGs. Using the Search Tool for Retrieval of Interacting Genes/Proteins (STRING) database, a protein–protein interaction (PPI) network was constructed, and the hub genes were identified by Cytoscape. And, after correcting for nonbiological effects between four datasets by Rank-In algorithm, we obtained a merged matrix. Furthermore, we adopted this merged matrix to evaluate immune infiltration by using CIBERSORT and single sample gene set enrichment analysis (ssGSEA). Finally, we calculated the correlation between hub genes and immune cells. Results Sixty-two integrated DEGs were identified. These DEGs were mainly enriched in 69 biological process (BP) terms and the ATP-binding cassette (ABC) transporters pathways. By applying 12 methods from Cytoscape plugin CytoHubba respectively, we selected final hub genes. The final hub genes consist of angiotensin Ⅰ converting enzyme (ACE), angiotensin converting enzyme 2 (ACE2), calsequestrin 2 (CASQ2) and TIMP metallopeptidase inhibitor 1 (TIMP1). CIBERSORT showed that monocytes (P P P P P P P P P P P P

Automated segmentation of cardiac pathology in MRI plays a significant role for diagnosis and treatment of some cardiac disease. In clinical practice, multi-modality MRI is widely used to improve the cardiac pathology segmentation, because it can provide multiple or complementary information. Recently, deep learning methods have presented implausible performance in multi-modality medical image segmentation. However, how to fuse the underlying multi-modality information effectively to segment the pathology with irregular shapes and small region at random locations, is still a challenge task. In this paper, a triple-attention-based multi-modality MRI fusion U-Net was proposed to learn complex relationship between different modalities and pay more attention on shape information, thus to achieve improved pathology segmentation. First, three independent encoders and one fusion encoder were applied to extract specific and multiple modality features. Secondly, we concatenate the modality feature maps and use the channel attention to fuse specific modal information at every stage of the three dedicate independent encoders, then the three single modality feature maps and channel attention feature maps are together concatenated to the decoder path. Spatial attention was adopted in decoder path to capture the correlation of various positions. Once more, we employ shape attention to focus shape-dependent information. Lastly, the training approach is made efficient by introducing deep supervision mechanism with object contextual representations block to ensure precisely boundary prediction. Our proposed network was evaluated on the public MICCAI 2020 Myocardial pathology segmentation dataset which involves patients suffering from myocardial infarction. Experiments on the dataset with three modalities demonstrate the effectiveness of fusion mode of our model, and attention mechanism can integrate various modality information well. We demonstrated that such a deep learning approach could better fuse complementary information to improve the segmentation performance of cardiac pathology.

Alloying is an effective approach to improve the catalysis performance of Pd-based catalysts for the selective hydrogenation of diolefins towards monoolefines. Herein, PdAgCu ternary nanoalloy catalysts were synthesised by a stepwise impregnation method for isoprene selective hydrogenation. The addition of a moderate amount of Ag and Cu to Pd significantly enhances the isoamylene selectivity in the isoprene hydrogenation, and decreases the non-desired over-hydrogenation. In addition, the loading molar ratio of PdAgCu with 3 : 2 : 3 as the optimal ternary nanoalloy composition maximizes the isoprene conversion (98%) and the monoolefins yield (92%). The surface structure of the catalyst was probed using H

Segmentation of multimodal brain tissues from 3D medical images is of great significance for brain diagnosis. It is required to create an automated and accurate segmentation based on deep-learning network due to the manual segmentation is time-consuming. However, how to segment medical images accurately and how to build neural network effectively with very limited computing resource, is still challenging task. To address these problems, we propose a novel model based on 3D fully convolutional network. More specifically, we apply multi-pathway architecture to feature extraction so as to effectively extract features from multi-modal MRI images. Different receptive field of feature have been extracted by adopting 3D dilated convolution in each pathway. By evaluating one-pathway model and key components of our model with a set of effective training schemes, we analyzed how these alternative methods affect the performance of experiments. Our proposed model was evaluated in the Brain Tumor Segmentation 2019 dataset (BraTS 2019), making an effective segmentation for the complete, core and enhancing tumor regions in Dice Similarity Coefficient metric (0.89, 0.78, 0.76) for the dataset. Also, we made a practice on BraTS 2018 using the same method with the Dice Similarity Coefficient metric of 0.90, 0.79, and 0.77 for the complete, core and enhancing tumor regions. Our method is inherently general and is a powerful tool to studies of medical images of brain tumors. Our code is available at https://github.com/JalexDooo/BrainstormTS .

In China, the incidence of arrhythmia has also increased to approximately 20% of all cardiovascular diseases. The incidence of cardiovascular diseases in China has certain characteristics, which are generally low in the south and high in the north, and they tend to be younger and growing. Permanent pacemaker implantation is currently the most effective means of treating arrhythmia and preventing sudden death. To explore the clinical application value of metoprolol in patients after permanent pacemaker implantation. Ninety patients with permanent dual-chamber pacemaker implantation in our hospital are selected and divided into a metoprolol group and a control group according to whether metoprolol is used one week after the operation and 45 patients in each group. After one postoperative week, the LVEF%, LVEDd, LAD, and E/A of the metoprolol and the control groups had no statistically significant differences p > 0.05 . Twelve months postoperatively, the E/A of the metoprolol group is higher than that of the control group p < 0.05 , and LVEDd and LAD are lower than those of the control group (P p > 0.05 in the values recorded immediately postoperatively. The NT-proBNP of the metoprolol group is lower than that of the control group p < 0.05 at 12 months following pacemaker implantation. At one week after surgery, QTd, Pd, and Tp-Te are not significantly different (P > 0.05) between the metoprolol group and the control group, whereas the QTd and Pd times in the metoprolol group are lower than those in the control group p < 0.05 at the 12-month follow-up. At one week postoperatively, the SDNN, SDANN, and RMSSD between the metoprolol and control groups did not show any statistically significant differences p > 0.05 . The SDANN of the metoprolol group is higher than that in the control group p < 0.05 in the 12-month evaluation. One week after the operation, the serum IL-6 and TNF-α levels are not significantly different between the metoprolol and control groups p > 0.05 . At 12 months after surgery, the serum IL-6 and TNF-α levels in the metoprolol group are lower than those in the control group p < 0.05 . The incidence of adverse events in the metoprolol group is 9.30% lower than 26.83% in the control group within 12 months after the operation p < 0.05 . The use of metoprolol in patients with permanent pacemaker implantation after surgery can reduce the expansionary remodeling of the left atrium and have less impact on the QT-dispersion and Pd time.

Significance In the approaching decades, food security will likely be more of an issue as there will be an increased demand for grain which will need to be met in an environmentally sustainable manner. To date, commercial transgenic maize has primarily targeted resistance to insects and herbicides. Here we describe a transgenic approach to improve the yield and yield stability of maize. We have demonstrated that increasing and extending the expression of a maize gene, zmm28, alters vegetative and reproductive growth parameters and significantly enhances yield in large-scale field trials conducted over multiple years. We conclude that alteration in expression of a native maize gene in maize can create a substantially positive change in a complex trait like grain yield., Increasing maize grain yield has been a major focus of both plant breeding and genetic engineering to meet the global demand for food, feed, and industrial uses. We report that increasing and extending expression of a maize MADS-box transcription factor gene, zmm28, under the control of a moderate-constitutive maize promoter, results in maize plants with increased plant growth, photosynthesis capacity, and nitrogen utilization. Molecular and biochemical characterization of zmm28 transgenic plants demonstrated that their enhanced agronomic traits are associated with elevated plant carbon assimilation, nitrogen utilization, and plant growth. Overall, these positive attributes are associated with a significant increase in grain yield relative to wild-type controls that is consistent across years, environments, and elite germplasm backgrounds.

Summary Functional stay‐green is a valuable trait that extends the photosynthetic period, increases source capacity and biomass and ultimately translates to higher grain yield. Selection for higher yields has increased stay‐green in modern maize hybrids. Here, we report a novel QTL controlling functional stay‐green that was discovered in a mapping population derived from the Illinois High Protein 1 (IHP1) and Illinois Low Protein 1 (ILP1) lines, which show very different rates of leaf senescence. This QTL was mapped to a single gene containing a NAC‐domain transcription factor that we named nac7. Transgenic maize lines where nac7 was down‐regulated by RNAi showed delayed senescence and increased both biomass and nitrogen accumulation in vegetative tissues, demonstrating NAC7 functions as a negative regulator of the stay‐green trait. More importantly, crosses between nac7 RNAi parents and two different elite inbred testers produced hybrids with prolonged stay‐green and increased grain yield by an average 0.29 megagram/hectare (4.6 bushel/acre), in 2 years of multi‐environment field trials. Subsequent RNAseq experiments, one employing nac7 RNAi leaves and the other using leaf protoplasts overexpressing Nac7, revealed an important role for NAC7 in regulating genes in photosynthesis, chlorophyll degradation and protein turnover pathways that each contribute to the functional stay‐green phenotype. We further determined the putative target of NAC7 and provided a logical extension for the role of NAC7 in regulating resource allocation from vegetative source to reproductive sink tissues. Collectively, our findings make a compelling case for NAC7 as a target for improving functional stay‐green and yields in maize and other crops.

Background/aim The early stage of atherosclerosis (AS) demonstrates a lipid-driven inflammatory cytokine increase. In the present study, we aimed to use ultrasound-targeted microbubble delivery (UTMD) therapy with the Endostar-loaded target microbubbles (MBs) to reduce AS-related inflammatory response. Materials and methods Normal and lipopolysaccharide (LPS) induced human umbilical vein endothelial cells (HUVECs) were placed in a parallel-plate flow chamber. MBs were perfused through the parallel-plate flow chamber to mimic physiological blood flow. Five groups were set up: G1: Negative control (normal HUVECs); G2: LPS control (LPS induced HUVECs); G3: ICAM-1-loaded-MBs (MBi); G4: Endostar-loaded-MBs (MBe) and G5: Endostar-ICAM-1-loaded-MBs (MBei). mRNA expression of inflammatory factors and release of inflammatory cytokines were detected by RT-PCR and ELISA, respectively. Results After treatment with MBei, the mRNA expression of cell adhesion molecule-1 (CD31) (p=0.004), endothelin-1 (ET-1) (p=0.010), von willebrand factor (vWF) (p=0.018), extracellular regulated protein kinases (ERK) (p=0.046) and nuclear factor kappa B (NF-κB) (p=0.003) were significantly reduced compared to LPS-induced HUVECs. Release of inflammatory cytokines including tissue factor (TF) (p=0.033), tissue factor pathway inhibitor (TF-PI) (p=0.019), ET-1 (p=0.014), vWF (p=0.030) and blood-coagulation factor VIIα (FVIIα) (p=0.000) were also significantly reduced compared to LPS-induced HUVECs. Conclusion UTMD therapy can inhibit the inflammatory response by reducing atherosclerotic-related inflammatory factors, suggesting a potential treatment at the early-stage of AS.

Gliomas are the most common brain tumors, which have a high mortality. Magnetic resonance imaging (MRI) is useful to assess gliomas, in which segmentation of multimodal brain tissues in 3D medical images is of great significance for brain diagnosis. Due to manual job for segmentation is time-consuming, an automated and accurate segmentation method is required. How to segment multimodal brain accurately is still a challenging task. To address this problem, we employ residual neural blocks and a U-Net architecture to build a novel network. We have evaluated the performances of different primary residual neural blocks in building U-Net. Our proposed method was evaluated on the validation set of BraTS 2020, in which our model makes an effective segmentation for the complete, core and enhancing tumor regions in Dice Similarity Coefficient (DSC) metric (0.89, 0.78, 0.72). And in testing set, our model got the DSC results of 0.87, 0.82, 0.80. Residual convolutional block is especially useful to improve performance in building model. Our proposed method is inherently general and is a powerful tool to studies of medical images of brain tumors.

The earth-to-air heat exchanger (EAHE) system, as a clean and efficient shallow geothermal energy application technology, has obvious effects in reducing the energy consumption of passive low-energy buildings. The traditional horizontal EAHE system is difficult to apply and popularize due to its large occupation, unfavorable shallow soil temperature, and difficulty in timely centralized discharge of condensed water. This paper proposes a new type of vertical earth-to-air heat exchanger (VEAHE) system. The VEAHE system has a number of advantages such as smaller occupation, efficient geothermal energy utilization, and centralized discharge of condensed water. In order to evaluate the influence of different parameters on the thermal performance of the VEAHE system, a mathematical model of the VEAHE system was developed. And, the data calculated by the model highly tallied with the experimental data. The results showed that laying thermal insulation layers at the outlet of risers will effectively restrain the interference of downcomers to risers. It is advisable to set thickness and length of the insulation layer at 30 mm and 3 m. Considering the compromise between thermal performance and construction costs of the VEAHE system, the length of the ducts at 30–50 m and the diameter at 150–250 mm are recommended. The air supply volume of a single shaft can reach 500–1200 m3/h as the air velocity reaches 3–7 m/s.

Background/Aim: Intraplaque neovascularization is often associated with plaque formation, development and instability, and clinical symptoms in atherosclerosis. The aim of the present study was to investigate a new strategy for treating athrosclerosis by ultrasound-targeted microbubble delivery (UTMD) targeting intraplaque neovascularization in an APOE-deficient mouse model of atherosclerosis. Materials and Methods: A mouse model of atherosclerosis was induced by feeding Apoe−/− mice a hypercholesterolemic diet and was verified with hematoxylin and eosin staining and intercellular adhesion molecule 1 (ICAM-1) expression. Targeted microbubbles (MB) were prepared by conjugating microbubbles with biotinylated antibody to ICAM1 (MBi) or with both biotinylated anti-ICAM1 and the angiogenesis inhibitor Endostar (MBie). The targeted microbubbles were analyzed with epifluorescence microscopy and flow cytometry. The animals with induced atherosclerotic plaques received MBi or MBie followed by UTMD treatment. Endostar treatment alone was given to other animals for comparison. Morphological assessment of atherosclerotic plaques was performed after treatment. The expression of angiogenesis marker CD31 was detected by immunohistochemical analysis. Results: Atherosclerotic plaques developed in the entire aorta with significant intraplaque ICAM-1 expression in the APOE-deficient mice following a 30-week hypercholesterolemic diet. Microbubbles were successfully conjugated with anti-ICAM-1 and Endostar, with a conjugation rate of 98.3% and 63.5%, respectively. UTMD with MBie significantly reduced the area of atherosclerotic plaque as compared to the model control (p

The response of leaf photosynthesis and metabolite profiles to ozone (O3) exposure ranging from 37 to 116 ppb was investigated in two soybean cultivars Dwight and IA3010 in the field under fully open-air conditions. Leaf photosynthesis, total non-structural carbohydrates (TNC) and total free amino acids (TAA) decreased linearly with increasing O3 levels in both cultivars with average decrease of 7% for an increase in O3 levels by 10 ppb. Ozone interacted with developmental stages and leaf ages, and caused higher damage at later reproductive stages and in older leaves. Ozone affected yield mainly via reduction of maximum rate of Rubisco carboxylation (Vcmax) and maximum rates of electron transport (Jmax) as well as a shorter growing season due to earlier onset of canopy senescence. For all parameters investigated the critical O3 levels (∼50 ppb) for detectable damage fell within O3 levels that occur routinely in soybean fields across the US and elsewhere in the world. Strong correlations were observed in O3-induced changes among yield, photosynthesis, TNC, TAA and many metabolites. The broad range of metabolites that showed O3 dose dependent effect is consistent with multiple interaction loci and thus multiple targets for improving the tolerance of soybean to O3.

Current background ozone (O3) concentrations over the northern hemisphere’s midlatitudes are high enough to damage crops and are projected to increase. Soybean (Glycine max) is particularly sensitive to O3; therefore, establishing an O3 exposure threshold for damage is critical to understanding the current and future impact of this pollutant. This study aims to determine the exposure response of soybean to elevated tropospheric O3 by measuring the agronomic, biochemical, and physiological responses of seven soybean genotypes to nine O3 concentrations (38–120 nL L−1) within a fully open-air agricultural field location across 2 years. All genotypes responded similarly, with season-long exposure to O3 causing a linear increase in antioxidant capacity while reducing leaf area, light absorption, specific leaf mass, primary metabolites, seed yield, and harvest index. Across two seasons with different temperature and rainfall patterns, there was a robust linear yield decrease of 37 to 39 kg ha−1 per nL L−1 cumulative O3 exposure over 40 nL L−1. The existence of immediate effects of O3 on photosynthesis, stomatal conductance, and photosynthetic transcript abundance before and after the initiation and termination of O3 fumigation were concurrently assessed, and there was no evidence to support an instantaneous photosynthetic response. The ability of the soybean canopy to intercept radiation, the efficiency of photosynthesis, and the harvest index were all negatively impacted by O3, suggesting that there are multiple targets for improving soybean responses to this damaging air pollutant.

Nitrogen (N) addition typically increases overall plant growth, but the nature of this response depends upon patterns of plant nitrogen allocation that vary throughout the growing season and depend upon canopy position. In this study seasonal variations in leaf traits were investigated across a canopy profile in Miscanthus (Miscanthus 9 giganteus) under two N treatments (0 and 224 kg ha � 1 ) to determine whether the growth response of Miscanthus to N fertilization was related to the response of photosynthetic capacity and nitrogen allocation. Miscanthus yielded 24.1 Mg ha � 1 in fertilized plots, a 40% increase compared to control plots. Photosynthetic properties, such as net photosynthesis (A), maximum rate of rubisco carboxylation (Vcmax), stomatal conductance (gs) and PSII efficiency (Fv’/Fm’), all decreased significantly from the top of the canopy to the bottom, but were not affected by N fertilization. N fertilization increased specific leaf area (SLA) and leaf area index (LAI). Leaf N concentration in different canopy layers was increased by N fertilization and the distribution of N concentration within canopy followed irradiance gradients. These results show that the positive effect of N fertilization on the yield of Miscanthus was unrelated to changes in photosynthetic rates but was achieved mainly by increased canopy leaf area. Vertical measurements through the canopy demonstrated that Miscanthus adapted to the light environment by adjusting leaf morphological and biochemical properties independent of nitrogen treatments. GPP estimated using big leaf and multilayer models varied considerably, suggesting a multilayer model in which Vcmax changes both through time and canopy layer could be adopted into agricultural models to more accurately predict biomass production in biomass crop ecosystems.

We investigated the individual effect of null mutations of each of the four sucrose-phosphate synthase (SPS) genes in Arabidopsis (SPSA1, SPSA2, SPSB and SPSC) on photosynthesis and carbon partitioning. Null mutants spsa1 and spsc led to decreases in maximum SPS activity in leaves by 80 and 13%, respectively, whereas null mutants spsa2 and spsb had no significant effect. Consistently, isoform-specific antibodies detected only the SPSA1 and SPSC proteins in leaf extracts. Leaf photosynthesis at ambient [CO₂] was not different among the genotypes but was 20% lower in spsa1 mutants when measured under saturating [CO₂] levels. Carbon partitioning at ambient [CO₂] was altered only in the spsa1 null mutant. Cold treatment of plants (4 °C for 96 h) increased leaf soluble sugars and starch and increased the leaf content of SPSA1 and SPSC proteins twofold to threefold, and of the four null mutants, only spsa1 reduced leaf non-structural carbohydrate accumulation in response to cold treatment. It is concluded that SPSA1 plays a major role in photosynthetic sucrose synthesis in Arabidopsis leaves, and decreases in leaf SPS activity lead to increased starch synthesis and starch turnover and decreased Ribulose 1,5-bisphosphate regeneration-limited photosynthesis but not ribulose 1·5-bisphosphate carboxylase/oxygenase (Rubisco)-limited photosynthesis, indicating a limitation of triose-phosphate utilization (TPU).

The earth is rapidly changing through processes such as rising [CO2], [O3], and increased food demand. By 2050 the projected atmospheric [CO2] and ground level [O3] will be 50% and 20% higher than today. To meet future agricultural demand, amplified by an increasing population and economic progress in developing countries, crop yields will have to increase by at least 50% by the middle of the century. FACE (Free Air Concentration Enrichment) experiments have been conducted for more than 20 years in various parts of world to estimate, under the most realistic agricultural conditions possible, the impact of the CO2 levels projected for the middle of this century on crops. The stimulations of crop seed yields by the projected CO2 levels across FACE studies are about 18% on average and up to ∼30% for the hybrid rice varieties and vary among crops, cultivars, nitrogen levels and soil moisture. The observed increase in crop yields under the projected CO2 levels fall short of what would be required to meet the projected future food demand, even with the most responsive varieties. Crop biomass production and seed yield is the product of photosynthetic solar energy conversion. Improvement in photosynthetic radiation use efficiency stands as the most promising opportunity allowing for major increases in crop yield in a future that portends major changes in climate and crop growing environments. Our advanced understanding of the photosynthetic process along with rapidly advancing capabilities in functional genomics, genetic transformation and synthetic biology promises new opportunities for crop improvement by greater photosynthesis and crop yield. Traits and genes that show promise for improving photosynthesis are briefly reviewed, including enhancing leaf photosynthesis capacity and reducing photorespiration loss, manipulating plant hormones’ responses for better ideotypes, extending duration of photosynthesis, and increasing carbon partitioning to the sink to alleviate feedback inhibition of photosynthesis.

The Farquhar–von Caemmerer–Berry (FvCB) model of photosynthesis has been widely used to estimate the photosynthetic C flux of plants under different growth conditions. However, the seasonal fluctuation of some photosynthesis parameters (e.g. the maximum carboxylation rate of Rubisco (Vcmax), the maximum electron transport rate (Jmax) and internal mesophyll conductance to CO2 transport (gm)) is not considered in the FvCB model. In this study, we investigated the patterns of the FvCB parameters during flag leaf development based on measured photosynthesis–intercellular CO2 curves in two cultivars of winter wheat (Triticum aestivum L.). Parameterised seasonal patterns of photosynthesis parameters in the FvCB model have subsequently been applied in order to predict the photosynthesis of flag leaves. The results indicate that the Gaussian curve characterises the dynamic patterns of Vcmax, Jmax and gm well. Compared with the model with fixed photosynthesis parameter values, updating the FvCB model by considering seasonal changes in Vcmax and Jmax during flag leaf development slightly improved predictions of photosynthesis. However, if the updated FvCB model incorporated the seasonal patterns of Vcmax and Jmax, and also of gm, predictions of photosynthesis was improved a lot, matching well with the measurements (R2 = 0.87, P

Wild-type (wt) Arabidopsis plants, the starch-deficient mutant TL46, and the near-starchless mutant TL25 were grown in hydroponics under two levels of nitrate, 0.2 versus 6 mm, and two levels of CO2, 35 versus 100 Pa. Growth (fresh weight and leaf area basis) was highest in wt plants, lower in TL46, and much lower in TL25 plants under a given treatment. It is surprising that the inability to synthesize starch restricted leaf area development under both low N (NL) and high N (NH). For each genotype, the order of greatest growth among the four treatments was high CO2/NH > low CO2/NH, > high CO2/NL, which was similar to low CO2/NL. Under high CO2/NL, wt and TL46 plants retained considerable starch in leaves at the end of the night period, and TL25 accumulated large amounts of soluble sugars, indicative of N-limited restraints on utilization of photosynthates. The lowest ribulose-1,5-bisphosphate carboxylase/oxygenase per leaf area was in plants grown under high CO2/NL. When N supply is limited, the increase in soluble sugars, particularly in the starch mutants, apparently accentuates the feedback and down-regulation of ribulose-1,5-bisphosphate carboxylase/oxygenase, resulting in greater reduction of growth. With an adequate supply of N, growth is limited in the starch mutants due to insufficient carbohydrate reserves during the dark period. A combination of limited N and a limited capacity to synthesize starch, which restrict the capacity to use photosynthate, and high CO2, which increases the potential to produce photosynthate, provides conditions for strong down-regulation of photosynthesis.

The experiment was conducted to investigate the heat transfer performance of wet flue gas in a vertical tube. The factors influencing the convective condensation of wet flue gas were experimentally investigated. The measured results indicate that the convective heat transfer of bulk flow and condensation heat transfer of vapor have significant contribution to the total heat transfer and the dominant transport mechanism is dependent upon the vapor fraction in mixture.

The kinetic properties of photosynthesis (both transient and steady-state) were monitored using three non-invasive techniques to evaluate limitations on triose-phosphate (triose-P) conversion to carbohydrate in rice. These included analyzing the O2 sensitivity of CO2 fixation and the assimilatory charge (AC) using gas exchange (estimate of the ribulose 1,5- bisphosphate pool) and measuring Photosystem II activity by chlorophyll fluorescence analysis under varying light, temperature and CO2 partial pressures. Photosynthesis was inhibited transiently upon switching from 20 to 2 kPa O2 (reversed O2 sensitivity), the degree of which was correlated with a terminal, steady-state suppression of low O2 enhancement of photosynthesis. Under current ambient levels of CO2 and moderate to high light, the transient pattern was more obvious at 18 °C than at 26 °C while at 34 °C no tra nsient response was observed. The transient inhibition at 18 °C ranged from 15% to 31% depending on the pre-measurement temperature. This pattern, symptomatic of feedback, was observed with increasing light and CO2 partial pressures with the degree of feedback decreasing from moderate (18 °C) up to high temperature (34 °C). Under feedback conditions, the rate of assimilation is shifted from being photorespiration limited to being triose-P utilization limited. Transitory changes in CO2 assimilation rates (A) under low O2 indicative of feedback coincided with a transitory drop in assimilatory charge (AC) and inhibition of electron transport. In contrast to previous studies with many C3 species, our studies indicate that rice shows susceptibility to feedback inhibition under moderate temperatures and current atmospheric levels of CO2.

l4 CO2-fixation in spinach occurs in the middle of the palisade mesophyll [Nishio et al. (1993) Plant Cell 5: 953], however, ninety percent of the blue and red light is attenuated in the upper twenty percent of a spinach leaf [Cui et al. (1991) Plant Cell Environ. 14: 493]. In this report, we showed that green light drives 14 C02-fixation deep within spinach leaves compared to red and blue light. Blue light caused fixation mainly in the palisade mesophyll of the leaf, whereas red light drove fixation slightly deeper into the leaf than did blue light. I4 C02-fixation measured under green light resulted in less fixation in the upper epidermal layer (guard cells) and upper most palisade mesophyll compared to red and blue light, but led to more fixation deeper in the leaf than that caused by either red or blue light. Saturating white, red, or green light resulted in similar maximal 14 CO2-fixation rates, whereas under the highest irradiance of blue light given, carbon fixation was not saturated, but it asymptotically approached the maximal 14 CO2-fixation rates attained under the other types of light. The importance of green light in photosynthesis is discussed.

The response of photosynthesis in the flag leaf of rice (Oryza sativa) to elevated CO2 or reduced O2 was investigated relative to other environmental factors using steadystate gas exchange techniques. We found under moderate conditions of temperature and photosynthetic flux density (PFD) (26°C and 700/nnoI quanta m~ 2 s~\ similar to growth conditions) photosynthesis in the flag leaf of rice during heading and grain filling saturated at near ambient levels of CO2, with a concomitant loss of O2 sensitivity, when a high stomatal conductance was maintained by high humidity (low vapor pressure deficit). Under 18°C there was near complete loss of O2 sensitivity of photosynthesis at normal ambient levels of CO2. This is in contrast to the large enhancement of photosynthesis by supra-atmospheric levels of CO2 and sub-atmospheric levels of O2 by suppression of photorespiration when there is no limitation on utilizing the initial product of CO2 assimilation (triose-P) as predicted from Ribulose-l,5-bisphosphate carboxylase/oxygenase (Rubisco) kinetic properties. Thus, loss of sensitivity to CO2 and O2 has been previously explained as a limitation on utilization of triose-P to synthesize carbohydrates. Under high PFD at 25°C, the rate of photosynthesis in rice declined over a period of hours around midday, while the intercellular levels of CO2 remained constant suggesting a limitation on utilization of photosynthate. Short-term fluctuations in climatic factors including temperature, light and humidity could result in a feedback limitation on photosynthesis in rice which may be exacerbated by rising CO2.

Chlorophyll fluorescence and internal patterns of 14 CO 2 fixation were measured in sun and shade leaves of spinach after treatment with various light intensities. When sun leaves were irradiated with 2000 μmol m -2 s -1 for 2h, F v /F M decreased by about 15%, but 14 CO 2 fixation was unaffected, whereas shade leaves exhibited a 21% decrease in F V /F M and a 25% decrease in 14 CO 2 fixation. Irradiation of sun and shade leaves with 4000 μmol m -2 s -1 for 4 h decreased F V /F M by 30% in sun leaves and 40% in shade leaves, while total 14 CO 2 fixation decreased by 41% in sun leaves and 55% in shade leaves. After light treatment, gradients of CO 2 fixation across leaves were determined by measuring 14 CO 2 fixed in paradermal leaf sections after a 10s pulse of 14 CO 2 . Gradients of 14 CO 2 fixation in control sun and shade leaves were identified when expressed on a relative basis and normalized for leaf depth. Treatment of leaves with 2000 μmol PAR m -2 s -1 for 2h did not alter patterns of carbon fixation across sun leaves, but slightly altered the pattern in shade leaves. In contrast, treatment of sun and shade leaves with 4000 μmol m -2 s -1 for 4h decreased carbon fixation more in the palisade mesophyll cells than in the spongy mesophyll cells of sun and shade leaves, and fixation in medial tissue of shade leaves was dramatically decreased compared to the adaxial and abaxial tissue. The interaction between leaf anatomy and biochemical parameters involved in tolerance to photoinhibition in spinach is discussed.

The BRASSINOSTEROID INSENSITIVE1 (BRI1) receptor kinase has recently been shown to possess tyrosine kinase activity, and preventing autophosphorylation of the tyrosine-831 regulatory site by site-directed mutagenesis enhances shoot growth. In this study, we characterized the increased leaf growth of Arabidopsis (Arabidopsis thaliana) plants expressing BRI1(Y831F)-Flag compared with BRI1-Flag (both driven by the native promoter and expressed in the bri1-5 weak allele background) and provide insights into the possible mechanisms involved. On average, relative leaf growth rate was increased 16% in the Y831F plants (in the bri1-5 background), and the gain of function of the Y831F-directed mutant was dominant in the wild-type background. Leaves were larger as a result of increased cell numbers and had substantially increased vascularization. Transcriptome analysis indicated that genes associated with brassinolide biosynthesis, secondary cell wall biosynthesis and vascular development, and regulation of growth were altered in expression and may contribute to the observed changes in leaf architecture and whole plant growth. Analysis of gas exchange and chlorophyll fluorescence indicated that Y831F mutant plants had higher rates of photosynthesis, and metabolite analysis documented enhanced accumulation of starch, sucrose, and several amino acids, most prominently glycine and proline. These results demonstrate that mutation of BRI1 can enhance photosynthesis and leaf growth/vascularization and may suggest new approaches to increase whole plant carbon assimilation and growth.

We investigated the individual effect of null mutations of each of the four sucrose-phosphate synthase (SPS) genes in Arabidopsis (SPSA1, SPSA2, SPSB and SPSC) on photosynthesis and carbon partitioning. Null mutants spsa1 and spsc led to decreases in maximum SPS activity in leaves by 80 and 13%, respectively, whereas null mutants spsa2 and spsb had no significant effect. Consistently, isoform-specific antibodies detected only the SPSA1 and SPSC proteins in leaf extracts. Leaf photosynthesis at ambient [CO₂] was not different among the genotypes but was 20% lower in spsa1 mutants when measured under saturating [CO₂] levels. Carbon partitioning at ambient [CO₂] was altered only in the spsa1 null mutant. Cold treatment of plants (4 °C for 96 h) increased leaf soluble sugars and starch and increased the leaf content of SPSA1 and SPSC proteins twofold to threefold, and of the four null mutants, only spsa1 reduced leaf non-structural carbohydrate accumulation in response to cold treatment. It is concluded that SPSA1 plays a major role in photosynthetic sucrose synthesis in Arabidopsis leaves, and decreases in leaf SPS activity lead to increased starch synthesis and starch turnover and decreased Ribulose 1,5-bisphosphate regeneration-limited photosynthesis but not ribulose 1·5-bisphosphate carboxylase/oxygenase (Rubisco)-limited photosynthesis, indicating a limitation of triose-phosphate utilization (TPU).

Here it is reported that sucrose synthase can be readily measured in growing wild tomato fruits (Lycopersicon chmielewskii) when suitable methods are adopted during fruit extraction. The enzyme also was present in fruit pericarp tissues, in seeds, and in flowers. To check for novel characteristics, the wild tomato fruit sucrose synthase was purified, by (NH(4))(2)SO(4) fraction and chromatography with DE-32, Sephadex G-200, and PBA-60, to one major band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The following characteristics were obtained: native protein relative molecular weight 380,000; subunit relative molecular weight 89,000; K(m) values with: sucrose 53 millimolar, UDP 18.9 micromolar, UDP-glucose 88 micromolar, fructose 8.4 millimolar; pH optima between 6.2 to 7.3 for sucrose breakdown and 7 to 9 for synthesis; and temperature optima near 50 degrees C. The enzyme exhibited a high affinity and a preference for uridylates. The enzyme showed more sensitivity to divalent cations in the synthesis of sucrose than in its breakdown. Sink strength in tomato fruits also was investigated in regard to sucrose breakdown enzyme activities versus fruit weight gain. Sucrose synthase activity was consistently related to increases in fruit weight (sink strength) in both wild and commercial tomatoes. Acid and neutral invertases were not, because the published invertase activity values were too variable for quantitative analyses regarding the roles of invertases in tomato fruit development. In rapidly growing fruits of both wild and commercially developed tomato plants, the activity of sucrose synthase per growing fruit, i.e. sucrose synthase peak activity X fruit size, was linearly related to final fruit size; and the activity exceeded fruit growth and carbon import rates by at least 10-fold. In mature, nongrowing fruits, sucrose synthase activities approached nil values. Therefore, sucrose synthase can serve as an indicator of sink strength in growing tomato fruits.

Plant productivity and yield are dependent on source-sink relationships, i.e. the capacity of source leaves to fix CO2 and the capacity of developing sink tissues and organs to assimilate and convert this fixed carbon into dry matter. Studies from our laboratories as well as others have demonstrated that rice productivity and yield are mainly sink-limited during its development because of limited capacity to utilize the initial photosynthetic product (triose phosphate). This limitation in triose phosphate utilization, evident at both the vegetative and reproductive stages of rice development, may be associated with limited capacity for carbohydrate synthesis in rice leaves (which are poor accumulators of starch) or feedback due to limited sink strength of developing seeds. Strategies in improving triose phosphate utilization by enhancing starch production in leaves and developing seeds by the expression of engineered genes for ADP glucose pyrophosphorylase, a key regulatory enzyme of starch biosynthesis, are discussed.

Limitations of carbon fixation within spinach leaves due to light and CO2 were investigated. Under equivalent photon fluxes, carbon fixation was higher when leaves were irradiated adaxially compared to abaxially. Maximal carbon fixation occurred in the middle of the palisade mesophyll under adaxial illumination, whereas, maximal carbon fixation occurred in the spongy mesophyll under abaxial illumination. Total carbon fixation and the pattern of carbon fixation across leaves were similar, when leaves were irradiated with 800 micromol quanta m(-2) s(-1) either adaxially alone or adaxially plus abaxially (1,600 micromol quanta m(-2) s(-1)). In contrast, when both leaf surfaces were irradiated simultaneously with 200 micromol quanta m(-2) s(-1), total carbon fixation increased and carbon fixation in the middle of the leaf was higher compared to leaves irradiated unilaterally with the low light. Feeding 14CO2 through either the adaxial or abaxial leaf surface did not change the pattern of carbon fixation across the leaf. Increasing 14CO2 pulse-feeding times from 5 s to 60 s allowed more 14CO2 to be fixed but did not change the pattern of 14CO2 fixation across the leaf. We concluded that in spinach, the distribution of both light and Rubisco activity within leaves has significant effects on the patterns of carbon fixation across leaves; whereas CO2 diffusion does not appear to affect the carbon fixation pattern within spinach leaves.

Wild-type Arabidopsis plants, the starch-deficient mutant TL46, and the near-starchless mutant TL25 were evaluated by noninvasive in situ methods for their capacity for net CO2 assimilation, true rates of photosynthetic O2 evolution (determined from chlorophyll fluorescence measurements of photosystem II), partitioning of photosynthate into sucrose and starch, and plant growth. Compared with wild-type plants, the starch mutants showed reduced photosynthetic capacity, with the largest reduction occurring in mutant TL25 subjected to high light and increased CO2 partial pressure. The extent of stimulation of CO2 assimilation by increasing CO2 or by reducing O2 partial pressure was significantly less for the starch mutants than for wild-type plants. Under high light and moderate to high levels of CO2, the rates of CO2assimilation and O2 evolution and the percentage inhibition of photosynthesis by low O2 were higher for the wild type than for the mutants. The relative rates of14CO2 incorporation into starch under high light and high CO2 followed the patterns of photosynthetic capacity, with TL46 showing 31% to 40% of the starch-labeling rates of the wild type and TL25 showing less than 14% incorporation. Overall, there were significant correlations between the rates of starch synthesis and CO2 assimilation and between the rates of starch synthesis and cumulative leaf area. These results indicate that leaf starch plays an important role as a transient reserve, the synthesis of which can ameliorate any potential reduction in photosynthesis caused by feedback regulation.

In situ measurements of 14C-CO2 incorporation into 40-[mu]m paradermal leaf sections of sun- and shade-grown spinach leaves were determined. Chlorophyll, carotenoid, and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) content in similar 40-[mu]m paradermal leaf sections was also measured. The carbon fixation gradient did not follow the leaf internal light gradient, which decreases exponentially across the leaf. Instead, the 14C-CO2 fixation was higher in the middle of the leaf. Contrary to expectations, the distribution of carbon fixation across the leaf showed that the spongy mesophyll contributes significantly to the total carbon reduced. Approximately 60% of the carboxylation occurred in the palisade mesophyll and 40% occurred in the spongy mesophyll. Carbon reduction correlated well with Rubisco content, and no correlation between chlorophyll and carotenoid content and Rubisco was observed in sun plants. The correlation among chlorophyll, carotenoids, Rubisco, and carbon fixation was higher in shade leaves than in sun leaves. The results are discussed in relation to leaf photosynthetic and biochemical measurements that generally consider the leaf as a single homogeneous unit.