Elevated ozone reduces photosynthetic carbon gain by accelerating leaf senescence of inbred and hybrid maize in a genotype-specific manner.

Exposure to elevated tropospheric ozone concentration ([O3 ]) accelerates leaf senescence in many C3 crops. However, the effects of elevated [O3 ] on C4 crops including maize (Zea mays L.) are poorly understood in terms of physiological mechanism and genetic variation in sensitivity. Using free air gas concentration enrichment, we investigated the photosynthetic response of 18 diverse maize inbred and hybrid lines to season-long exposure to elevated [O3 ] (~100 nl L-1 ) in the field. Gas exchange was measured on the leaf subtending the ear throughout the grain filling period. On average over the lifetime of the leaf, elevated [O3 ] led to reductions in photosynthetic CO2 assimilation of both inbred (-22%) and hybrid (-33%) genotypes. There was significant variation among both inbred and hybrid lines in the sensitivity of photosynthesis to elevated [O3 ], with some lines showing no change in photosynthesis at elevated [O3 ]. Based on analysis of inbred line B73, the reduced CO2 assimilation at elevated [O3 ] was associated with accelerated senescence decreasing photosynthetic capacity and not altered stomatal limitation. These findings across diverse maize genotypes could advance the development of more O3 tolerant maize and provide experimental data for parameterization and validation of studies modeling how O3 impacts crop performance.

High-Throughput Phenotyping of Maize Leaf Physiological and Biochemical Traits Using Hyperspectral Reflectance.

High-throughput, noninvasive field phenotyping has revealed genetic variation in crop morphological, developmental, and agronomic traits, but rapid measurements of the underlying physiological and biochemical traits are needed to fully understand genetic variation in plant-environment interactions. This study tested the application of leaf hyperspectral reflectance (λ = 500-2,400 nm) as a high-throughput phenotyping approach for rapid and accurate assessment of leaf photosynthetic and biochemical traits in maize (Zea mays). Leaf traits were measured with standard wet-laboratory and gas-exchange approaches alongside measurements of leaf reflectance. Partial least-squares regression was used to develop a measure of leaf chlorophyll content, nitrogen content, sucrose content, specific leaf area, maximum rate of phosphoenolpyruvate carboxylation, [CO2]-saturated rate of photosynthesis, and leaf oxygen radical absorbance capacity from leaf reflectance spectra. Partial least-squares regression models accurately predicted five out of seven traits and were more accurate than previously used simple spectral indices for leaf chlorophyll, nitrogen content, and specific leaf area. Correlations among leaf traits and statistical inferences about differences among genotypes and treatments were similar for measured and modeled data. The hyperspectral reflectance approach to phenotyping was dramatically faster than traditional measurements, enabling over 1,000 rows to be phenotyped during midday hours over just 2 to 4 d, and offers a nondestructive method to accurately assess physiological and biochemical trait responses to environmental stress.

O risco de infecções genitais em mulheres usuárias de dispositivo intrauterino / The risk of genital infections in women using intrauterine device

Dispositivos intra-uterinos (DIU) são amplamente usados como método contraceptivo e têm uma possível associação com infecções do trato genital inferior. Objetivo: Avaliar se o uso de DIU está associado com infecções do trato genital e por quais patógenos. Métodos: Revisão sistemática de estudos dos bancos de dados PubMed, Highwire-Stanford e Google Scholar usando as seguintes palavras-chave: "cytology IUD" OR "IUD AND cytology" OR "cytology" OR "cytological techniques" OR "cytological AND techniques" OR "cell biology" OR "cell AND biology". Resultados: Foram encontrados inicialmente 2817 artigos e selecionados 16, que obedeciam os critérios de inclusão. Com base nestes estudos, o microorganismo associado ao uso de DIU e principal causa de doença inflamatória pélvica é o Actinomyces spp. Há risco 14 vezes maior de presença do Actinomyces spp. em usuárias de DIU em relação a não usuárias. No entanto, parece haver uma maior depuração aparente de infecção por Papilomavírus humano (HPV) entre usuárias de DIU de cobre. Conclusão: Há uma associação entre o uso de DIU e algumas infecções genitais, tal como vaginose bacteriana; no entanto, o agente mais evidentemente associado é o Actinomyces spp. Há uma possível maior depuração de infecção por HPV entre usuárias de DIU de cobre.

Intrauterine devices (IUDs) are widely used contraceptive methods that have a possible association with lower genital tract infections. Objective: To assess whether IUD is associated with genital tract infection and which pathogens cause it. Methods: Systematic review of studies in PubMed database, Highwire-Stanford, and Google Scholar using the following keywords: "cytology IUD," OR "IUD AND cytology" OR "cytology" OR "cytological techniques," OR "cytological AND techniques," OR "cell biology," OR "cell" and "biology". Results: Sixteen out of the 2,817 initial articles were selected using the inclusion criteria. On the basis of these studies, the microorganisms that can colonize the IUD, the main acute pelvic inflammatory disease occasioner is Actinomyces spp. There is a risk 14 times greater of the presence of Actinomyces spp. in IUD users than in non-users. However, there would be a higher apparent depuration of human papillomavirus (HPV) infection among copper T users. Conclusion: There is an association between the use of IUD and some genital infections such as bacterial vaginosis; however, more evidently associated with Actinomyces spp. There is a possible higher depuration of infection by HPV among copper T users.

Selected reaction monitoring to determine protein abundance in Arabidopsis using the Arabidopsis proteotypic predictor.

In reverse genetic knockout (KO) studies that aim to assign function to specific genes, confirming the reduction in abundance of the encoded protein will often aid the link between genotype and phenotype. However, measuring specific protein abundance is particularly difficult in plant research, where only a limited number of antibodies are available. This problem is enhanced when studying gene families or different proteins derived from the same gene (isoforms), as many antibodies cross react with more than one protein. We show that utilizing selected reaction monitoring (SRM) mass spectrometry allows researchers to confirm protein abundance in mutant lines, even when discrimination between very similar proteins is needed. Selecting the best peptides for SRM analysis to ensure that protein- or gene-specific information can be obtained requires a series of steps, aids, and interpretation. To enable this process in Arabidopsis (Arabidopsis thaliana), we have built a Web-based tool, the Arabidopsis Proteotypic Predictor, to select candidate SRM transitions when no previous mass spectrometry evidence exists. We also provide an in-depth analysis of the theoretical Arabidopsis proteome and its use in selecting candidate SRM peptides to establish assays for use in determining protein abundance. To test the effectiveness of SRM mass spectrometry in determining protein abundance in mutant lines, we selected two enzymes with multiple isoforms, aconitase and malate dehydrogenase. Selected peptides were quantified to estimate the abundance of each of the two mitochondrial isoforms in wild-type, KO, double KO, and complemented plant lines. We show that SRM protein analysis is a sensitive and rapid approach to quantify protein abundance differences in Arabidopsis for specific and highly related enzyme isoforms.

Mitochondrial malate dehydrogenase lowers leaf respiration and alters photorespiration and plant growth in Arabidopsis.

Malate dehydrogenase (MDH) catalyzes a reversible NAD(+)-dependent-dehydrogenase reaction involved in central metabolism and redox homeostasis between organelle compartments. To explore the role of mitochondrial MDH (mMDH) in Arabidopsis (Arabidopsis thaliana), knockout single and double mutants for the highly expressed mMDH1 and lower expressed mMDH2 isoforms were constructed and analyzed. A mmdh1mmdh2 mutant has no detectable mMDH activity but is viable, albeit small and slow growing. Quantitative proteome analysis of mitochondria shows changes in other mitochondrial NAD-linked dehydrogenases, indicating a reorganization of such enzymes in the mitochondrial matrix. The slow-growing mmdh1mmdh2 mutant has elevated leaf respiration rate in the dark and light, without loss of photosynthetic capacity, suggesting that mMDH normally uses NADH to reduce oxaloacetate to malate, which is then exported to the cytosol, rather than to drive mitochondrial respiration. Increased respiratory rate in leaves can account in part for the low net CO(2) assimilation and slow growth rate of mmdh1mmdh2. Loss of mMDH also affects photorespiration, as evidenced by a lower postillumination burst, alterations in CO(2) assimilation/intercellular CO(2) curves at low CO(2), and the light-dependent elevated concentration of photorespiratory metabolites. Complementation of mmdh1mmdh2 with an mMDH cDNA recovered mMDH activity, suppressed respiratory rate, ameliorated changes to photorespiration, and increased plant growth. A previously established inverse correlation between mMDH and ascorbate content in tomato (Solanum lycopersicum) has been consolidated in Arabidopsis and may potentially be linked to decreased galactonolactone dehydrogenase content in mitochondria in the mutant. Overall, a central yet complex role for mMDH emerges in the partitioning of carbon and energy in leaves, providing new directions for bioengineering of plant growth rate and a new insight into the molecular mechanisms linking respiration and photosynthesis in plants.

Remodeled respiration in ndufs4 with low phosphorylation efficiency suppresses Arabidopsis germination and growth and alters control of metabolism at night.

Respiratory oxidative phosphorylation is a cornerstone of cellular metabolism in aerobic multicellular organisms. The efficiency of this process is generally assumed to be maximized, but the presence of dynamically regulated nonphosphorylating bypasses implies that plants can alter phosphorylation efficiency and can benefit from lowered energy generation during respiration under certain conditions. We characterized an Arabidopsis (Arabidopsis thaliana) mutant, ndufs4 (for NADH dehydrogenase [ubiquinone] fragment S subunit 4), lacking complex I of the respiratory chain, which has constitutively lowered phosphorylation efficiency. Through analysis of the changes to mitochondrial function as well as whole cell transcripts and metabolites, we provide insights into how cellular metabolism flexibly adapts to reduced phosphorylation efficiency and why this state may benefit the plant by providing moderate stress tolerance. We show that removal of the single protein subunit NDUFS4 prevents assembly of complex I and removes its function from mitochondria without pleiotropic effects on other respiratory components. However, the lack of complex I promotes broad changes in the nuclear transcriptome governing growth and photosynthetic function. We observed increases in organic acid and amino acid pools in the mutant, especially at night, concomitant with alteration of the adenylate content. While germination is delayed, this can be rescued by application of gibberellic acid, and root growth assays of seedlings show enhanced tolerance to cold, mild salt, and osmotic stress. We discuss these observations in the light of recent data on the knockout of nonphosphorylating respiratory bypass enzymes that show opposite changes in metabolites and stress sensitivity. Our data suggest that the absence of complex I alters the adenylate control of cellular metabolism.