Field and genetic evidence support the photosynthetic performance index (PIABS) as an indicator of rice grain yield.

The rice breeding process for grain yield could be effectively enhanced by developing efficient tools that accelerate plant selection through the rapid determination of reliable predictors. In this study, we have described various associations between grain yield and photosynthetic parameters, which can be easily and quickly obtained using a non-invasive technique on the flag leaf during the anthesis stage. Among the analyzed photosynthetic parameters, the photosynthetic performance index (PIABS) stood out due to its strong association with grain yield. A genome-wide association analysis conducted on plants from a rice diversity panel at the tillering stage revealed the presence of a quantitative trait locus on chromosome 9. This locus was characterized by a group of candidate chloroplastic genes that exhibited contrasting haplotypes for PIABS. An analysis of these haplotypes revealed a clear division into two groups. One group consisted of haplotypes linked to high values of PIABS, which were predominantly associated with Japonica spp. subpopulations. The other group consisted of haplotypes linked to low values of PIABS, which were exclusively associated with Indica spp. subpopulations. Japonica spp. genotypes exhibited higher values in the yield component panicle weight compared with the Indica spp. genotypes. The findings of this study indicate that PIABS could serve as an early predictor of yield parameters during the tillering stage in rice breeding processes.

Patterns of physiological parameters and nitrogen partitioning in flag leaf explain differential grain protein content in rice.

The grain protein content (GPC) in rice is low, and more efforts with agronomic and molecular approaches were performed to increase them. However, the rice research focusing on the plant physiological behaviour that modulates the phenomenon of grain protein filling is very scarce. This work contains physiological parameters related to photosynthetic activity in the flag leaf in the grain filling period and N partitioning assays of high (Nutriar) and traditional (Camba) GPC cultivars. Results indicated a higher photosynthetic capacity, a better capacity to provide CO2 to the chloroplast and a healthier PSII structure in Camba relative to Nutriar. Chlorophyll fluorescence parameters decreased more steeply over time in the high protein variety, and a strong negative correlation was observed between GPC and PSII structure parameters. N content in the flag leaf at anthesis showed lower values and higher remobilisation during the grain filling period in Nutriar compared to Camba. The results of this work suggested that the inactivation of some PSII structures in higher GPC cultivars is associated with N remobilisation and would contribute to an increase in the free N available to be translocated to the grain.

Close relationship between the state of the oxygen evolving complex and rice cold stress tolerance.

The results of the present work suggested a relationship between the growth stability and functional/structural parameters associated to the primary photochemistry and oxygen evolving complex (OEC) in tolerant rice plants under suboptimal low temperatures (SLT) stress. This was concluded from the absence of changes in net photosynthetic rate and in fraction of reaction centers to reduce quinone A, and very small changes in P680 efficiency to trap and donate electrons to quinone A and in fraction of active OEC in tolerant plants under cold stress but not in sensitive plants. The SLT stress also induced OEC activity limitations in both genotypes, but in a greater extent in sensitive plants. However, an assay using an artificial electron donor to replace OEC indicated that the P680+ capacity to accept electrons was not altered in both genotypes under SLT stress from the beginning of the stress treatment, suggesting that the OEC structure stability is related to rice SLT tolerance to sustain the photosynthesis. This hypothesis was also supported by the fact that tolerant plants but not sensitive plants did not alter the gene expression and protein content of PsbP under SLT stress, an OEC subunit with a role in stabilizing of OEC structure.

Redox homeostasis in the growth zone of the rice leaf plays a key role in cold tolerance.

We analysed the cellular and molecular changes in the leaf growth zone of tolerant and sensitive rice varieties in response to suboptimal temperatures. Cold reduced the final leaf length by 35% and 51% in tolerant and sensitive varieties, respectively. Tolerant lines exhibited a smaller reduction of the leaf elongation rate and greater compensation by an increased duration of leaf growth. Kinematic analysis showed that cold reduced cell production in the meristem and the expansion rate in the elongation zone, but the latter was compensated for by a doubling of the duration of cell expansion. We performed iTRAQ proteome analysis on proliferating and expanding parts of the leaf growth zone. We identified 559 and 542 proteins, of which 163 and 210 were differentially expressed between zones, and 96 and 68 between treatments, in the tolerant and sensitive lines, respectively. The categories protein biosynthesis and redox homeostasis were significantly overrepresented in the up-regulated proteins. We therefore measured redox metabolites and enzyme activities in the leaf growth zone, demonstrating that tolerance of rice lines to suboptimal temperatures correlates with the ability to up-regulate enzymatic antioxidants in the meristem and non-enzymatic antioxidants in the elongation zone.

Polyamines and Legumes: Joint Stories of Stress, Nitrogen Fixation and Environment.

Polyamines (PAs) are natural aliphatic amines involved in many physiological processes in almost all living organisms, including responses to abiotic stresses and microbial interactions. On other hand, the family Leguminosae constitutes an economically and ecologically key botanical group for humans, being also regarded as the most important protein source for livestock. This review presents the profuse evidence that relates changes in PAs levels during responses to biotic and abiotic stresses in model and cultivable species within Leguminosae and examines the unreviewed information regarding their potential roles in the functioning of symbiotic interactions with nitrogen-fixing bacteria and arbuscular mycorrhizae in this family. As linking plant physiological behavior with "big data" available in "omics" is an essential step to improve our understanding of legumes responses to global change, we also examined integrative MultiOmics approaches available to decrypt the interface legumes-PAs-abiotic and biotic stress interactions. These approaches are expected to accelerate the identification of stress tolerant phenotypes and the design of new biotechnological strategies to increase their yield and adaptation to marginal environments, making better use of available plant genetic resources.

Defining novel plant polyamine oxidase subfamilies through molecular modeling and sequence analysis.

BACKGROUND: The polyamine oxidases (PAOs) catabolize the oxidative deamination of the polyamines (PAs) spermine (Spm) and spermidine (Spd). Most of the phylogenetic studies performed to analyze the plant PAO family took into account only a limited number and/or taxonomic representation of plant PAOs sequences. RESULTS: Here, we constructed a plant PAO protein sequence database and identified four subfamilies. Subfamily PAO back conversion 1 (PAObc1) was present on every lineage included in these analyses, suggesting that BC-type PAOs might play an important role in plants, despite its precise function is unknown. Subfamily PAObc2 was exclusively present in vascular plants, suggesting that t-Spm oxidase activity might play an important role in the development of the vascular system. The only terminal catabolism (TC) PAO subfamily (subfamily PAOtc) was lost in Superasterids but it was present in all other land plants. This indicated that the TC-type reactions are fundamental for land plants and that their function could being taken over by other enzymes in Superasterids. Subfamily PAObc3 was the result of a gene duplication event preceding Angiosperm diversification, followed by a gene extinction in Monocots. Differential conserved protein motifs were found for each subfamily of plant PAOs. The automatic assignment using these motifs was found to be comparable to the assignment by rough clustering performed on this work. CONCLUSIONS: The results presented in this work revealed that plant PAO family is bigger than previously conceived. Also, they delineate important background information for future specific structure-function and evolutionary investigations and lay a foundation for the deeper characterization of each plant PAO subfamily.

Rice tolerance to suboptimal low temperatures relies on the maintenance of the photosynthetic capacity.

The purpose of this research was to identify differences between two contrasting rice cultivars in their response to suboptimal low temperatures stress. A transcriptomic analysis of the seedlings was performed and results were complemented with biochemical and physiological analyses. The microarray analysis showed downregulation of many genes related with PSII and particularly with the oxygen evolving complex in the sensitive cultivar IR50. Complementary studies indicated that the PSII performance, the degree of oxygen evolving complex coupling with the PSII core and net photosynthetic rate diminished in this cultivar in response to the stress. However, the tolerant cultivar Koshihikari was able to maintain its energy equilibrium by sustaining the photosynthetic capacity. The increase of oleic acid in Koshihikari could be related with membrane remodelling of the chloroplasts and hence contribute to tolerance. Overall, these results work as a ground for future analyses that look forward to characterize possible mechanisms to tolerate this stress.

The alkaline tolerance in Lotus japonicus is associated with mechanisms of iron acquisition and modification of the architectural pattern of the root.

The response of fifty-four Lotus japonicus ecotypes, and of six selected ecotypes was investigated under alkaline conditions. Sensitive, but not tolerant ecotypes, showed interveinal chlorosis under all alkalinity conditions and high mortality under extreme alkalinity. Interveinal chlorosis was associated with Fe deficiency, as a reduced Fe2+ shoot content was observed in all sensitive ecotypes. In addition, some showed a decline in photosynthesis rate and PSII performance compared to the control. In contrast, some tolerant ecotypes did not change these parameters between treatments. Alkaline tolerance could be explained by a mechanism of Fe acquisition and a root structural modification. This conclusion was based on the fact that all tolerant, but not the sensitive ecotypes, presented high ferric reductase oxidase activity under alkaline stress compared to the control, and a Herringbone root pattern modification. On this basis, the analysis of these mechanisms of alkaline tolerance could be used in screening programs for the selection of new tolerant genotypes in the Lotus genus.

Una perspectiva global de los cuidados paliativos / Global perspective of palliative care

Antecedentes. Los cuidados paliativos no adelantan ni retrasan la muerte, sino que constituyen un verdadero sistema de apoyo y soporte para el paciente y su familia. En relación con los pacientes pediátricos, oncológicos y no oncológicos, la cobertura paliativa específica en domicilio es prácticamente inexistente. Es imprescindible establecer mecanismos de coordinación entre los distintos niveles implicados (domiciliario, atención primaria y hospitalaria) para asegurar la continuidad de la asistencia a lo largo de todo el proceso. Desarrollo. Se hizo una revisión bibliográfica de las distintas publicaciones y sitios Web como MedScape, Google académico, además de la colaboración de los expertos en cuidados paliativos que nos visitaron en el taller subregional dado en Tegucigalpa M.D.C. el pasado 11 de noviembre del 2011, proporcionándonos aportes muy importantes. Conclusión. Es fundamental para el alivio del sufrimiento, el desarrollo de programas de cuidados paliativos, el facilitar la disponibilidad de opioides y el mejorar la formación de los profesionales en cuidados paliativos...

Determination of reactive oxygen species in salt-stressed plant tissues.

Reactive oxygen species (ROS) participate in signaling events that regulate ion channel activity and gene expression. However, excess ROS exert adverse effects that stem from their interaction with macromolecules. Thus, the assessment of the effects of salinity on ROS changes are central to understanding how plants respond and cope with this stress. ROS determination in salt-stressed plants poses specific challenges. On the one hand, salinity comprises osmotic and ion-specific effects which may, in turn, have different effects on ROS production. On the other hand, changes in ROS production may happen when tissues from salinized plants are subject to water potential (Ψ) changes when incubated in non-isosmotic solutions. This chapter provides detailed accounts of methods for ROS detection in tissues from salt-stressed plants and includes suggestions for avoiding artifacts when dealing with such tissues.

Polyamine catabolism is involved in response to salt stress in soybean hypocotyls.

The possible relationship between polyamine catabolism mediated by copper-containing amine oxidase and the elongation of soybean hypocotyls from plants exposed to NaCl has been studied. Salt treatment reduced values of all hypocotyl growth parameters. In vitro, copper-containing amine oxidase activity was up to 77-fold higher than that of polyamine oxidase. This enzyme preferred cadaverine over putrescine and it was active even under the saline condition. On the other hand, saline stress increased spermine and cadaverine levels, and the in vivo copper-containing amine oxidase activity in the elongation zone of hypocotyls. The last effect was negatively modulated by the addition of the copper-containing amine oxidase inhibitor N,N'-diaminoguanidine. In turn, plants treated with the inhibitor showed a significant reduction of reactive oxygen species in the elongation zone, even in the saline situation. In addition, plants grown in cadaverine-amended culture medium showed increased hypocotyl length either in saline or control conditions and this effect was also abolished by N,N'-diaminoguanidine. Taken together, our results suggest that the activity of the copper-containing amine oxidase may be partially contributing to hypocotyl growth under saline stress, through the production of hydrogen peroxide by polyamine catabolism and reinforce the importance of polyamine catabolism and hydrogen peroxide production in the induction of salt tolerance in plants.

Polyamine oxidase activity contributes to sustain maize leaf elongation under saline stress.

The possible involvement of apoplastic reactive oxygen species produced by the oxidation of free polyamines in the leaf growth of salinized maize has been studied here. Salt treatment increased the apoplastic spermine and spermidine levels, mainly in the leaf blade elongation zone. The total activity of polyamine oxidase was up to 20-fold higher than that of the copper-containing amine oxidase. Measurements of H(2)O(2), *O(2)(-), and HO* production in the presence or absence of the polyamine oxidase inhibitors 1,19-bis-(ethylamine)-5,10,15 triazanonadecane and 1,8-diamino-octane suggest that, in salinized plants, the oxidation of free apoplastic polyamines by polyamine oxidase by would be the main source of reactive oxygen species in the elongation zone of maize leaf blades. This effect is probably due to increased substrate availability. Incubation with 200 microM spermine doubled segment elongation, whereas the addition of 1,19-bis-(ethylamine)-5,10,15 triazanonadecane and 1,8-diamino-octane to 200 microM spermine attenuated and reversed the last effect, respectively. Similarly, the addition of MnCl(2) (an *O(2)(-) dismutating agent) or the HO* scavenger sodium benzoate along with spermine, annulled the elongating effect of the polyamine on the salinized segments. As a whole, the results obtained here demonstrated that, under salinity, polyamine oxidase activity provides a significant production of reactive oxygen species in the apoplast which contributes to 25-30% of the maize leaf blade elongation.

Leaf expansion in grasses under salt stress.

Restriction of leaf growth is among the earliest visible effects of many stress conditions, including salinity. Because leaves determine radiation interception and are the main photosynthetic organs, salinity effects on leaf expansion and function are directly related to yield constraints under saline conditions. The expanding zone of leaf blades spans from the meristem to the region in which cells reach their final length. Kinematic methods are used to describe cell division and cell expansion activities. Analyses of this type have indicated that the reduction in leaf expansion by salinity may be exerted through effects on both cell division and expansion. In turn, the components of vacuole-driven cell expansion may be differentially affected by salinity, and examination of salinity effects on osmotic and mechanical constraints to cell expansion have gradually led to the identification of the gene products involved in such control. The study of how reactive oxygen species affect cell expansion is an emerging topic in the study of salinity's regulation of leaf growth.