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Pharmacological and surgical interventions do not improve postural control and gait effectively in people with Parkinson's disease (PD). An innovative and promising therapeutic intervention is perturbation-based balance training (PBT).To perform a systematic review to summarise the current evidence for PBT on postural control and gait in people with PD. Intervention studies including PBT, in isolation or associated with other physical interventions, were included.PubMed, SciELO, PEDro and Cochrane databases were searched between June 2000 and March 2020.This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, and is registered in the PROSPERO database (CRD42020203961). The quality of evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation. Studies were assessed for methodological quality using the PEDro scale. Two of the authors reviewed the search results and selected studies using predefined selection criteria. No restrictions based on severity of PD, time since diagnosis or age were used.Eleven studies were selected for final evaluation. Most outcomes were downgraded in quality of evidence, mainly because of publication bias and limitations. The most consistent results indicate that PBT can improve postural control and gait in people with PD, including a reduction in the number of falls and a decrease in the severity of PD.PBT may be a promising option for the treatment of people with PD, and an adjunct to conventional physiotherapeutic treatment. However, deficiencies in the methodological quality and quality of evidence of studies included in this review have limited the reliability of the conclusions.PROSPERO CRD42020203961.

An important health-related problem of obesity is reduced stance stability, leading to increased chance of falling. In the present experiment, we aimed to compare stability in quiet and in dynamic body balance between women with morbid obesity (n = 13, body mass index [BMI] > 40 Kg/m2, mean age = 38.85 years) and with healthy body weight (lean) (n = 13; BMI < 25 Kg/m2, mean age = 37.62 years), evaluating the extent to which quiet and dynamic balance stability are associated with plantar sensibility. Quiet stance was evaluated in different visual and support base conditions. The dynamic task consisted of rhythmic flexion—extension movements at the hip and shoulder, manipulating vision availability. The plantar sensibility threshold was measured through application of monofilaments on the feet soles. The results showed that the morbidly obese, in comparison with the lean women, had higher plantar sensibility thresholds, and a reduced balance stability in quiet standing. Mediolateral stance stability on the malleable surface was strongly correlated with plantar sensibility in the obese women. Analysis of dynamic balance showed no effect of obesity and weaker correlations with plantar sensibility. Our results suggest that reduced plantar sensibility in morbidly obese women may underlie their diminished stance stability, while dynamic balance control seems to be unaffected by their reduced plantar sensibility.

Arginine (Arg) metabolism is associated with many cellular and developmental processes in plants and proline, nitric oxide (NO) and polyamines (PAs) have a wide range of physiological functions in plants, including increased tolerance to environmental stresses. This study aimed to test the hypothesis that Arg spraying would stimulate the synthesis of proline, NO and PAs, reducing the oxidative damage caused by water deficit (WD) and increasing drought tolerance of sugarcane plants. Sugarcane plants were sprayed with water or Arg 1 mM, and subjected to WD by gradual addition of polyethylene glycol (PEG-8000) to the nutrient solution. As references, sugarcane plants were grown in nutrient solution without PEG-8000 and sprayed or not with Arg. Our data indicate that exogenous Arg supply improved leaf gas exchange during water deficit and enhanced the root antioxidative protection of sugarcane plants during the recovery period. Arg supply prevented the proline accumulation induced by water deficit and then the main pathway for proline synthesis is likely through glutamate instead of arginine. Although Arg is a substrate for NO and PAs production, supplying Arg had only slight effects in both NO and PAs levels. The spraying of amino acids capable of reducing the harmful effects of drought, such as Arg, can be an alternative to improve crop growth under field conditions.

Freezing of gait (FoG) is one of the main reasons for movement initiation disorders and abnormal coupling of posture and gait in Parkinson's disease (PD). Patients with FoG have poor postural control when compared to patients without FoG. However, the nature of the interrelationship between FoG and domains of postural control remains unknown. The aim of this study was to estimate the association between different domains of postural control and severity of FoG in patients with moderate-to-severe PD. Thirty patients with idiopathic PD with FoG (age range 45-80 years, Hoehn & Yahr stages 3 and 4) participated in the study. We evaluated objective (FoG-ratio during turning task) and subjective (New Freezing of Gait Questionnaire, NFoG-Q) measures of FoG severity, reactive postural adjustments in response to an external perturbation, first step anticipatory adjustment for step initiation and quiet standing stability. In the multiple regression analysis, step initiation was the strongest significant correlation of the NFoG-Q score explaining 23% of the variance of the assessment. For the objective FoG measure, mediolateral CoP amplitude in quiet standing and mediolateral CoP amplitude in step initiation explained 39% of the variance of the FoG-ratio. As main conclusions, this study identified the association between objective and subjective measure for FoG severity and postural control domains. The results support conducting step initiation training during rehabilitation of individuals with FoG.

Muscle fatigue accumulated during a soccer game can be a critical element to athletic performance. The aim of this study was to analyze the feasibility of evaluating the effect of muscle fatigue of the support leg in soccer players postural stability and muscular activation of the stabilizing muscles of the ankle in the performance of a power kick. Six university soccer players were evaluated. Muscular fatigue was induced by means of repeated oscillations of the swing leg. Results indicated that fatigue did not significantly affect velocity of the kicking leg and postural stability while kicking. Electromyographic analysis revealed that fatigue induced decreased activation of the medial gastrocnemius and increased activation of the soleus muscles in the period following foot-ball contact. These results show the feasibility of analyzing the effect of fatigue on dynamic balance and muscular activation in the performance of a power kicking task.

People with Parkinson's disease (PwPD) showed impairments of balance control which can be aggravated by the presence of higher interlateral postural asymmetry caused by a distinct dopaminergic loss in the substantia nigra between cerebral hemispheres.We evaluate asymmetries between the more and the less affected leg in PwPD in responses to unanticipated stance perturbations.Sixteen 16 PwPD participated in the experiment that consisted of recovering a stable upright stance, keeping the feet in place, in response to a perturbation caused by a sudden release of a load equivalent to 7 % of the participant's body mass. Anterior displacement and velocity of the center of pressure (CoP), the latency of gastrocnemius medialis muscle (GM) activation onset, rate of GM activation, and normalized magnitude of muscular activation were analyzed.Analysis revealed significantly rate (p = 0.04) and magnitude (p = 0.02) higher activation of GM in the less affected limb. No significant effects of the leg were found for GM activation latency or CoP-related variables.There is a higher contribution of the less affected leg in automatic postural responses in PwPD.

In response to sudden perturbations of stance stability, muscles of both legs are activated for balance recovery. In conditions that one of the legs has a reduced capacity to respond, the opposite leg is predicted to compensate by responding more powerfully to restore stable upright stance. In this investigation, we aimed to evaluate between-leg compensatory control in automatic postural responses to sudden perturbations in a situation in which plantar flexor muscles of a single leg were fatigued. Young participants were evaluated in response to a series of perturbations inducing forward body sway, with a focus on activation of plantar flexor muscles: lateral and medial gastrocnemii and soleus. Muscular responses were analyzed through activation magnitude and latency of muscular activation onset. For evaluation of balance and postural stability, we also analyzed the center of pressure and upper trunk displacement and weight-bearing asymmetry between the legs. Responses were assessed in three conditions: pre-fatigue, under single-leg fatigue, and following the recovery of muscular function. Results showed (a) compensation of the non-fatigued leg through the increased magnitude of muscular activation in the first perturbation under fatigue; (b) adaptation in the non-fatigued leg over repetitive perturbations, with a progressive decrement of muscular activation over trials; and (c) maintenance of increased muscular activation of the non-fatigued leg following fatigue dissipation. These findings suggest that the central nervous system is able to modulate the descending motor drive individually for each leg's muscles apparently based on their potential contribution for the achievement of the behavioral aim of recovering stable body balance following stance perturbations.

People who are obese sustain very high foot pressures when standing, with potential consequences to their feet soles’ cutaneous sensibility. In the current investigation, we performed a detailed assessment of foot sole sensibility in women with morbid obesity ( n = 13; age = 38.85, SD = 8.09 years) status in comparison with leaner women ( n = 13; age = 37.62, SD = 7.10 years). We estimated tactile feet sole sensibility through graduated monofilament light touch applied at several hotspots of both feet soles, covering the toes, metatarsal heads, midfoot internal and lateral arches, and heel. Intergroup comparisons per foot sole region indicated significantly lower sensibility for the group with morbid obesity under the fifth and third metatarsal heads, midfoot lateral and internal arches and heel. We found a large variation across the sole regions, with the lowest difference between the obese and lean groups observed under the hallux (18%) and the largest difference observed under the lateral arch of the midfoot (76%). Correlation analyses between body weight and sensibility scores revealed a significant positive correlation among participants who were leaner ( rs = 0.56, p = 0.05) but not among participants who were obese ( rs = –0.06, p = 0.83). Mainly, our results showed that morbid obesity was associated with significantly higher cutaneous sensibility thresholds, with large variability of the sensibility deficit across different regions of both feet soles. Due to its functional relevance for body balance control, reduced sensibility thresholds among women who are morbidly obese may have implications for stance stability.

Age-related changes in presynaptic inhibition (PSI) have not been observed during gait initiation, which requires anticipatory postural adjustment (APA). As APA is centrally modulated and is impaired in older compared to young adults, here we aimed to study the presynaptic control and co-contraction levels in the ankle muscles during gait initiation in older compared to young adults. Fifteen older (age range 65–80 years) and 15 young adults (age range 19–30 years) performed a gait initiation task on a force platform under 3 conditions: (i) without electrical stimulation; (ii) test Hoffman reflex (H-reflex); and (iii) conditioned H-reflex. H-reflexes were evoked on the soleus muscle when the APA amplitude exceeded 10%–20% of the average baseline mediolateral force. Participants also performed quiet stance as a control task. Results showed that both age groups presented similar PSI levels during quiet stance (p = .941), while in the gait initiation older adults presented higher PSI levels, longer duration, and lower amplitude of APA than young adults (p < .05). Older adults presented higher co-contraction ratio in both tasks than young adults (p < .05). Correlations between the PSI levels and the APA amplitude (r = −0.61, p = .008), and between the PSI levels and the co-contraction ratio during gait initiation (r = −0.64, p = .005) were found for older adults only. APA amplitude explained 49% of the variance of the PSI levels (p = .003). Our findings suggest that older compared to young adults have increased presynaptic control to compensate for the decreased supraspinal modulation on impaired APAs during gait initiation.

Background Continuous oscillation of the support base requires anticipatory and reactive postural adjustments to maintain a stable balance. In this context, postural control flexibility or the ability to adjust balance mechanisms following the requirements of the environment is needed to counterbalance the predictable, continuous perturbation of body balance. Considering the inflexibility of postural responses in individuals with Parkinson's disease (PD), maintaining stability in the support base's continuous oscillations may be challenging. Varying the frequency of platform oscillation is an exciting approach to assess the interactions between reactive and anticipatory adjustments. Research question This study aimed to analyze postural responses of individuals with PD on an oscillatory support base across different frequencies. Methods Thirty participants with moderate PD diagnosis (M = 64.47 years, SD = 8.59; Hoehn and Yahr scale 3) and fifteen healthy age-matched controls (M = 65.8 years, SD = 4.2) were tested. Subjects maintained a dynamic balance on a platform oscillating in sinusoidal translations. Four oscillation frequencies were evaluated in different trials that ranged from 0.2 to 0.8 Hz in steps of 0.2 Hz. Results Analysis showed similar performance between PD and healthy participants, with modulation of amplitudes of head displacement, center of pressure, center of mass and feet-head coordination to platform oscillation frequency. Discussion Our findings suggest a preserved ability of individuals with PD to dynamically control body balance on a support base with predictable oscillatory translations.

No presente estudo foram avaliados os efeitos de treinamento baseado em perturbações imprevisíveis da base de suporte em indivíduos com bloqueio de marcha por doença de Parkinson (BMDP,) em respostas posturais automáticas e movimentos compensatórios a perturbações do equilíbrio. Indivíduos com BMDP foram pseudo-aleatoriamente para o grupo experimental, treinamento de recuperação de equilíbrio por meio de perturbações imprevisíveis em uma plataforma móvel (TRE, n = 9), ou para o grupo de controle ativo de treinamento de resistência (TF, n = 10). Ambos os grupos de treinamento realizaram exercícios duas vezes por semana durante 4 semanas. As avaliações foram realizadas antes, após 24 h e após um mês (retenção) do término dos treinamentos. Os resultados indicaram que o TRE levou a uma redução no número de quedas e a respostas reativas mais estáveis a perturbações imprevisíveis, com diminuição de amplitude de deslocamento, pico de velocidade e tempo de pico do centro de pressão. Alguns ganhos em respostas reativas observados logo após o fim do treinamento persistiram na avaliação de retenção. Como importante implicação clínica, ambos os treinamentos parecem ter levado à redução de incidência de eventos de bloqueio de marcha no cotidiano dos participantes. Como conclusão, nossos resultados indicam que o treinamento baseado em perturbações posturais melhorou o controle de respostas posturais reativas e movimentos compensatórios em indivíduos com BMDP, levando à redução do risco de queda em consequência de perturbação imprevisível do equilíbrio corporal In the present study, effects of training based on unpredictable perturbations of the support base were evaluated in individuals with freezing of gait (FOG) due to Parkinson\'s disease in automatic postural responses and compensatory movements to balance perturbations. Individuals with FOG were pseudorandomly either to the experimental group, perturbation-based balance training through unpredictable perturbations on a moveable platform (PBBT, n = 9), or to the active control group of resistance training (RT, n = 10). Both training groups performed exercises twice a week for 4 weeks. The outcomes were evaluated before, after 24h and after one month (retention) of the end of the training. Results indicated that the PBBT led to reduced number of falls and to more stable reactive responses to unpredictable perturbations, with decreased amplitude, peak of velocity and peak time of the center of pressure. Some gains in reactive responses observed immediately after the training were preserved in the retention assessment. As an important clinical implication, both training sessions seem to have led to reduced incidence of freezing of gait events in the participants\' daily lives. In conclusion, our results indicated that training based on unpredictable postural perturbations improved the control of reactive postural responses and compensatory movements in individuals with FOG, leading to a reduction in the risk of falling as a result of unpredictable perturbation of body balance

In response to sudden perturbations of stance stability, muscles of both legs are activated for balance recovery. In conditions that one of the legs has a reduced capacity to respond, the opposite leg is predicted to compensate by responding more powerfully to restore stable upright stance. In this investigation, we aimed to evaluate between-leg compensatory control in automatic postural responses to sudden perturbations in a situation in which plantar flexor muscles of a single leg were fatigued. Young participants were evaluated in response to a series of perturbations inducing forward body sway, with a focus on activation of plantar flexor muscles: lateral and medial gastrocnemii and soleus. Muscular responses were analyzed through activation magnitude and latency of muscular activation onset. For evaluation of balance and postural stability, we also analyzed the center of pressure and upper trunk displacement and weight-bearing asymmetry between the legs. Responses were assessed in three conditions: pre-fatigue, under single-leg fatigue, and following the recovery of muscular function. Results showed (a) compensation of the non-fatigued leg through the increased magnitude of muscular activation in the first perturbation under fatigue; (b) adaptation in the non-fatigued leg over repetitive perturbations, with a progressive decrement of muscular activation over trials; and (c) maintenance of increased muscular activation of the non-fatigued leg following fatigue dissipation. These findings suggest that the central nervous system is able to modulate the descending motor drive individually for each leg's muscles apparently based on their potential contribution for the achievement of the behavioral aim of recovering stable body balance following stance perturbations.

A sugarcane MYB present in the culm induces suberin biosynthesis and is involved both with fatty acid and phenolics metabolism. Few transcription factors have been described as regulators of cell wall polymers deposition in C4 grasses. Particularly, regulation of suberin biosynthesis in this group of plants remains poorly understood. Here, we showed that the sugarcane MYB transcription factor ShMYB78 is an activator of suberin biosynthesis and deposition. ShMYB78 was identified upon screening genes whose expression was upregulated in sugarcane internodes undergoing suberization during culm development or triggered by wounding. Agrobacterium-mediated transient expression of ShMYB78 in Nicotiana benthamiana leaves induced the ectopic deposition of suberin and its aliphatic and aromatic monomers. Further, the expression of suberin-related genes was induced by ShMYB78 heterologous expression in Nicotiana benthamiana leaves. ShMYB78 was shown to be a nuclear protein based on its presence in sugarcane internode nuclear protein extracts, and protoplast transactivation assays demonstrated that ShMYB78 activates the promoters of the sugarcane suberin biosynthetic genes β-ketoacyl-CoA synthase (ShKCS20) and caffeic acid-O-methyltransferase (ShCOMT). Our results suggest that ShMYB78 may be involved in the transcriptional regulation of suberin deposition, from fatty acid metabolism to phenylpropanoid biosynthesis, in sugarcane internodes.

Urea is a product of arginine catabolism in plants and its Nitrogen is recycled into the plant metabolism as ammonium after hydrolysis by urease. The eu3-a soybean mutant is null for the Ni insertion protein (UreG) necessary for urease activity. No UreG protein nor any activity of the urease enzymes is detectable in these eu3-a mutants. In order to understand the mechanisms of nitrogen cycling in soybean and the possible physiological benefits to N metabolism, eu3-a (urease-null) and control soybean near-isogenic Eu3 plants were studied. They were grown to two different developmental stages (vegetative-V5 and reproductive-R5) with 15 mM nitrate as the sole source of nitrogen. Growth and biochemical parameters (such as amino acid, nitrate, and polyamine pools) were evaluated in leaves. Gene transcript levels were determined for some enzymes related to Arg catabolism, together with those of the DUR3 active urea transporter and the UreG Ni-insertion accessory protein, whose transcript was confirmed to be absent in eu3-a. The absence of urease activity in the eu3-a null plants did not affect growth or yield although there was a substantial and progressive accumulation of urea in the leaves. Metabolic changes occurred mainly in the pool of amino acids and in the expression of genes related to the pathway of Arg degradation. There are indications that the pathway may be diverted to form polyamines, but to a limited extent. Thus, considering both developmental stages, the degradation of Arg to urea and Orn remains the main path for nitrogen recycling from Arg, despite the progressive accumulation of urea and consequently immobilization of N.

Reactive responses to balance perturbations have been shown to be improved by training. This investigation aimed to compare the effects of block and random training perturbation schedules on stability gains of compensatory arm and leg movements in response to unpredictable large-magnitude balance perturbations. Perturbations were produced by means of sudden displacements of the support base, associating mode (rotation, translation, combined), direction, and velocity of platform motion. Healthy young participants were assigned to one of three groups: random, block, and control. For the random group, perturbation sequence was unpredictable. For the block group, each balance perturbation was repeated over blocks of four trials. Controls were tested only, serving as reference of first trial responses in the post-test. Evaluation was made through a scale rating stability of compensatory arm and leg movements (CALM). We probed immediate and persistence gains (1-week retention), in addition to generalizability to perturbations of higher velocity and to dual-tasking (mental subtraction). In the post-test both the block and random groups achieved higher leg and global scores in comparison with controls in the most challenging perturbations. In retention and transfer tests, results for the global score indicated higher values for the random than for the block and control groups. These results support the conclusion that high but not low contextual interference in perturbation-based balance training leads to enduring and generalizable increased stability gains of compensatory limb movements in response to unpredictable balance perturbations.

Introducao: As fissuras labiopalatinas estao entre as malformacoes de maior incidencia entre as anomalias congenitas. O Hospital de Reabilitacao de Anomalias Craniofaciais da Universidade de Sao Paulo, em Bauru, assiste a essa clientela de toda a America Latina por meio de uma equipe interdisciplinar de referencia. Como o tratamento adequado demanda varios anos de intervencao e cuidados, as familias das criancas com esse tipo de anomalia acabam se deparando com barreiras de carater financeiro e geografico que dificultam o acesso a terapia. Diante disso, o uso de ferramentas digitais na comunicacao entre profissionais da saude e os responsaveis pelos pacientes e um potencial recurso na transmissao de conhecimento. Objetivo: Criar e avaliar um ambiente virtual de aprendizagem sobre o desenvolvimento de criancas com anomalias craniofaciais, usando tecnicas de terapia ocupacional. Metodo: Foi criado um ambiente virtual (website) usando e adaptando o Health-Related Web Site Evaluation Form Emory. O website foi entao avaliado por cinco terapeutas ocupacionais e cinco fonoaudiologos e o resultado foi submetido a analise descritiva e tratamento quanti-qualitativo, tambem usando as caracteristicas e formas de analise do Emory. Resultados: A qualidade do site foi considerada “Adequada” por 81,1% dos avaliadores, enquanto o conteudo por faixa etaria foi considerado “Excelente” por 94,3%. Conclusao: O uso do ambiente virtual no tratamento de criancas com fissuras labiopalatinas foi relevante, mostrando-se adequado e com conteudo excelente ao fim ao qual se destina. Isso indica, portanto, que o desenvolvimento tecnologico pode beneficiar processos terapeuticos e facilitar o acesso a este tratamento especifico.

The scale for evaluation of compensatory arm and leg movements (CALM) was developed to evaluate balance stability recovery after unpredictable displacements of the support base in the mediolateral direction. The mediolateral perturbations are applied in three modes: rotation, translation or combined rotation-translation, to either side, in three platform peak velocities: 20º-20 cm/s (low), 30º-30cm/s (intermediate) or 0º-40 cm/s (high), keeping peak acceleration of 500o/s2(cm/s2) and displacement amplitude of 7o (cm) constant across perturbations. The factors perturbation mode (3), direction (2) and velocity (3) of platform displacement are combined to generate 18 distinct stance perturbations. To create the context of unpredictability, perturbations are pseudorandomly sequenced. To become aware of the stance perturbations, participants watch a video demonstrating a person responding to the different platform perturbations included in the protocol. After video watching, subjects are warmed up for 5 min. with global movements. Initial feet positions are marked on the support base with adhesive tapes (5-cm width). Other adhesive tape marks are fixed 15 cm away from the outer border of the feet to either side, in parallel to the feet orientation. The initial participant’s posture on the platform is keeping the Romberg’s stance, with the feet oriented forward, touching each other, maintaining both arms relaxed hanging beside the trunk, and palms of the hands lightly touching the upper legs. Participants wear a safety harness supported by two ropes tied at the shoulders height with the other end attached overhead. The participant’s aim across perturbations is to recover balance after support base displacements trying to maintain the initial body posture. Participants’ responses are filmed from behind using a commercial digital camera (Sony), for off-line analysis based on the CALM scale.

Generation of automatic postural responses (APRs) scaled to magnitude of unanticipated postural perturbations is required to recover upright body stability. In the current experiment, we aimed to evaluate the effect of previous postural perturbations on APR scaling under conditions in which the current perturbation is equal to or different from the previous perturbation load inducing unanticipated forward body sway. We hypothesized that the APR is scaled from the association of the current perturbation magnitude and postural responses to preceding perturbations. Evaluation was made by comparing postural responses in the contexts of progressive increasing versus decreasing magnitudes of perturbation loads. Perturbation was applied by unanticipatedly releasing a cable pulling the body backwards, with loads corresponding to 6%, 8% and 10% of body mass. We found that the increasing as compared to the decreasing load sequence led to lower values of (a) displacement and (b) velocity of center of pressure, and of activation rate of the muscle gastrocnemius medialis across loads. Muscular activation onset latency decreased as a function increasing loads, but no significant effects of load sequence were found. These results lead to the conclusion that APRs to unanticipated perturbations are scaled from the association of somatosensory feedback signaling balance instability with feedforward control from postural responses to previous perturbations.

Contains fulltext : 208625.pdf (Publisher’s version ) (Open Access) Following unpredictable large-magnitude stance perturbations diverse patterns of arm and leg movements are performed to recover balance stability. Stability of these compensatory movements could be properly estimated through qualitative evaluation. In the present study, we present a scale for evaluation of compensatory arm and leg movements (CALM) in response to unpredictable displacements of the support base in the mediolateral direction. We tested the CALM scale for intra- and inter-rater reliability, correlation with kinematics of arm and leg movement amplitudes, and sensitivity to mode (rotation, translation and combined) and magnitude (velocity) of support base displacements, and also to perturbation-based balance training. Results showed significant intra- and inter-rater coefficients of agreement, ranging from moderate (0.46-0.53) for inter-rater reliability in the arm and global scores, to very high (0.87-0.99) for inter-rater leg scores and all intra-rater scores. Analysis showed significant correlation values between scale scores and the respective movement amplitudes both for arm and leg movements. Assessment of sensitivity revealed that the scale discriminated the responses between perturbation modes, platform velocities, in addition to higher balance recovery stability as a result of perturbation-based balance training. As a conclusion, the CALM scale was shown to provide adequate integrative evaluation of compensatory arm and leg movements for balance recovery stability after challenging stance perturbations, with potential application in fall risk prediction.

The soybean eu3-a mutant (formerly, eu3-e1) lacks all ureolytic activity. Eu3 encodes urease accessory (Ni insertion) protein, UreG. Eu3 (Glycine max v1.1 Glyma08g08970.1) is the only UreG-encoding gene in the soybean genome. Here we show that the eu3-a lesion is a 2.4 kb deletion, beginning 50 bp upstream of the transcription start, and covering 94 % of the deduced amino acid sequence of UreG, explaining the urease activity-null phenotype of eu3-a. We established near-isogenic lines (NILs), eu3-a versus Eu3, and confirmed a striking accumulation of endogenous urea in eu3-a and none in Eu3, and the greater resistance of eu3-a leaf discs to external urea. However, incubation of discs in light alleviated urea sensitivity in Eu3, apparently by providing C skeletons for urea-released NH3. Hence, urea, endogenous and exogenous, is apparently less toxic than urea-derived NH3. eu3-a and Eu3 plants, however, did not differ in seed Ni content, nor in pool sizes of metabolites that generate urea via arginine. The NILs differed in patterns of nodulation by Bradyrhizobium japonicum and by Bradyrhizobium elkanii. Ureases have been reported to be fungitoxic. However, eu3-a and Eu3 NIL seedlings were equally sensitive to the pathogenic Basidiomycete fungus, Rhizoctonia solani. Since eu3-a accumulates at least some apo-urease, we examined a specific anti-fungal role of the seed urease in seedlings of a second NIL pair, differing in the presence (Eu1) and absence (eu1-a) of the seed urease. Again, this second NIL pair exhibited equal sensitivity to R. solani. To our knowledge, we report only the second test of fungal resistance influenced by urease levels in intact plants.

Due to diverse human activities zinc (Zn) may reach phytotoxic levels in the soil. Here, we evaluated the differential sensibility of three Brazilian tree species from the Fabaceae to increasing soil Zn concentrations and its physiological response to cope with excess Zn. A greenhouse experiment was conducted with the species: Mimosa caesalpiniaefolia, Erythrina speciosa and Schizolobium parahyba, and the addition of 0, 200, 400 and 600 mg Zn kg−1 to the soil. Plants were harvested after three months of cultivation, and growth, root symbiosis, biochemical markers and elemental composition were analyzed. Soil Zn addition reduced seedling growth, irrespective of the species, with a strong reduction in M. caesalpiniaefolia. Regarding root symbiosis, in N2-fixing species, nitrogenase activity was reduced by the highest Zn concentrations. Zn addition caused plants nutritional imbalances, mainly in roots. The content of photosynthetic pigments in leaves decreased up to 40%, suggesting that high Zn contents interfered with its biosynthesis, and altered the content of foliar polyamines and free amino acids, depending on the species and the soil Zn concentration. Zn toxicity in M. caesalpiniaefolia plants was observed at available soil Zn concentrations greater than 100 mg kg−1 (DTPA-extractable), being the most sensitive species and E. speciosa was moderately sensitive. S. parahyba was a moderately tolerant species, which seems to be related to polyamines accumulation and to mycorrhizal association. This last species has the potential for revegetation of areas with moderately high soil Zn concentration and for phytostabilization purposes. Future research evaluating the tolerance to multiple metal stress under field conditions should confirm S. parayba suitability in Zn contaminated areas of tropical regions.

Soil contamination by heavy metals is a serious problem to humans due to its high level of toxicity. The heavy metal lead (Pb) is commonly used in industries and if the disposal of residues that contain this element is not done properly may result in tragic consequences to the organisms. In this experiment we assessed the potential of a forrage leguminous, Canavalia gladiata, to phytoremediate lead-contaminated soil under mycorrhizal influence. The experimental design was composed of 4 Pb doses (0, 250, 500, and 1000 mg kg(-1) of soil) and the plants were inoculated or uninoculated with arbuscular mycorrhizal fungi (AMF). We observed that the nodulation was severely affected by the presence of Pb independently of the mycorrhizal status; most of the elements analyzed were affected independently of the mycorrhizal status with exception of P. The mycorrhizal colonization was able to restrict the entrance of Pb in plants under high concentrations of Pb but promoted it's accumulation in both organs under intermediate concentrations of this element. Besides the mycorrhization did not promote plant growth under Pb stress, the use of this plant may be considered to be used for phytostabilization purposes.

Heavy metals (HMs) are environmental pollutants of great concern to humans because of their high potential toxicity. Lead is a HM that is present in the soil in very small amounts, but anthropogenic activities have increased its content in some locations, which can make these areas unproductive or inappropriate for crop production. However, there are some plants that can grow in contaminated soils and, thus, can be useful for the removal or stabilisation of such contaminants. In addition, plants that are not able to tolerate high concentrations of HMs in the soil can become tolerant or increase their performance when associated with arbuscular mycorrhizal (AM) fungi. Accordingly, this study was carried out to verify whether the inoculation of Glomus etunicatum, an AM fungus species, in Calopogonium mucunoides would influence plant tolerance to increasing concentrations of Pb in the soil. The experimental design was completely randomised, in a 2 × 4 factorial design, and the treatments consisted of inoculation (or not) with the AM fungus, G. etunicatum, and the addition of four Pb concentrations (0, 250, 500 or 1,000 mg kg−1) to the soil. The results showed that the association of C. mucunoides with G. etunicatum promoted biomass production, and nutrient uptake (P, S and Fe) was also positively influenced by mycorrhization. The malondialdehyde content was higher in non-mycorrhizal leaves, suggesting a reduction in the damage to membranes by lipid peroxidation in plants associated with mycorrhizae. However, the Pb concentration in the shoots did not differ between the mycorrhizal and non-mycorrhizal plants. The results of our study suggest that the AM symbiosis can be considered very effective in contributing to the tolerance of C. mucunoides to Pb.

A poluição do solo com metais pesados tem aumentado significativamente nos últimos anos, devido à ação antrópica. Diversas técnicas podem ser utilizadas para reverter ou minimizar a condição de contaminação do solo, porém muitas delas são prejudiciais ao solo. Uma alternativa é a utilização da fitorremediação, já que as plantas possuem a capacidade de absorver elementos do solo e, dessa maneira, promover sua descontaminação com teores excessivos de metais e outros elementos potencialmente tóxicos. A associação de plantas com fungos micorrízicos arbusculares (FMAs) pode influenciar a absorção desses elementos. Com o objetivo de avaliar o potencial fitorremediador de plantas de Stizolobium aterrimum associadas ou não a FMAs em solos com concentrações crescentes de Pb, realizou-se um experimento sob condições de casa de vegetação, em esquema fatorial 4 x 2. Os tratamentos consistiram na adição de quatro doses de Pb (0, 250, 500 e 1.000 mg dm-3) e da inoculação ou não de FMA. Os resultados mostraram que a planta foi tolerante ao Pb nas doses utilizadas. A associação com FMA não influenciou a absorção de Pb pela planta. No entanto, a micorrização influenciou a fixação biológica de N2, observando-se maior atividade da enzima nitrogenase em plantas micorrizadas. Apesar dos bons resultados obtidos com relação à tolerância dessa planta ao Pb, mais estudos precisam ser realizados acerca da absorção desse elemento, principalmente em solo multicontaminado, que é a realidade encontrada em sistemas poluídos. Heavy metal pollution of soils has increased significantly in the last years owing to anthropic action. Several techniques can be used to revert or to minimize soil contamination, although many of these techniques are harmful to the soil. An alternative is to use a new technique, called phytoremediation, based on the ability of plants to take up elements from soils with excessive high levels of metals or of other potentially toxic elements and thus contribute to soil decontamination. The inoculation of plants with arbuscular mycorrhizal fungi (AMF) can influence the absorption of these elements. The phytoremediation potential of Stizolobium aterrimum plants with or without AMF in soils with increasing lead concentrations was evaluated in a greenhouse experiment, in a 4 x 2 factorial design. The treatments consisted of the addition of four Pb rates (0, 250, 500 and 1000 mg dm-3) to the soil where black velvet bean plants associated or not with Glomus etunicatum AMF where grown. The results showed that black velvet bean was Pb tolerant at the tested rates. The association with AMF did not influence the Pb plant uptake. However, the mycorrhiza influenced biological nitrogen fixation by increasing the activity of the enzyme nitrogenase in mycorrhizal plants. Despite the good results obtained in relation to Pb tolerance of black velvet bean, further studies on the uptake of this element are needed, above all in the case of multicontaminated soils, as actually observed in polluted systems.

Nitrogen fixation of the nodule of soybean is highly sensitive to oxygen deficiency such as provoked by waterlogging of the root system. This study aimed to evaluate the effects of flooding on N metabolism in nodules of soybean. Flooding resulted in a marked decrease of asparagine (the most abundant amino acid) and a concomitant accumulation of γ-aminobutyric acid (GABA). Flooding also resulted in a strong reduction of the incorporation of (15)N2 in amino acids. Nodule amino acids labelled before flooding rapidly lost (15)N during flooding, except for GABA, which initially increased and declined slowly thereafter. Both nitrogenase activity and the expression of nifH and nifD genes were strongly decreased on flooding. Expression of the asparagine synthetase genes SAS1 and SAS2 was reduced, especially the former. Expression of genes encoding the enzyme glutamic acid decarboxylase (GAD1, GAD4, GAD5) was also strongly suppressed except for GAD2 which increased. Almost all changes observed during flooding were reversible after draining. Possible changes in asparagine and GABA metabolism that may explain the marked fluctuations of these amino acids during flooding are discussed. It is suggested that the accumulation of GABA has a storage role during flooding stress.

A greenhouse pot experiment was conducted to evaluate the potential of three Brazilian leguminous woody species, Mimosa caesalpiniaefolia, Erythrina speciosa and Schizolobium parahyba, for the revegetation of lead- (Pb-) contaminated areas. The response of seedlings to increasing Pb concentrations (0, 250, 500 and 1000 mg kg(-1)) in the soil was studied. In addition to Pb accumulation and translocation, the following parameters were assessed: chlorophyll, nitrate, ammonia, lipid peroxidation (MDA) and free amino acid content; seedling growth; and nitrogenase activity. No differences were observed in the germination of woody species seeds sown in soils with or without Pb addition. M. caesalpiniaefolia did not show visual symptoms of Pb toxicity, while the other two species demonstrated stress symptoms, including reduced shoot biomass yield, leaf area and height. Biochemical analyses of plant tissues revealed markedly different responses to increasing Pb concentrations, such as changes in foliar soluble amino acid composition in S. parahyba; changes in ammonia and nitrate content in E. speciosa, M. caesalpiniaefolia and S. parahyba; and changes in MDA content in S. parahyba. The levels of chlorophyll a and b and carotenoid were affected in the species studied. For the Nitrogen-fixing (N(2)-fixing) species E. speciosa, an increase of Pb in the soil affected nodule formation and growth, which led to reduced nitrogenase activity in seedlings. The concentration of Pb in shoots and roots increased with the Pb concentration in soil. However, most of the Pb absorbed accumulated in the roots, and only a small fraction was translocated to aboveground parts. These findings were confirmed by the low bioconcentration factor (BCF) and translocation factor (TF) values for the three species. The tolerance index (TI) values suggested that M. caesalpiniaefolia, a N(2)-fixing tree, was the species that was most tolerant to high Pb concentrations in soil, while E. speciosa and S. parahyba showed moderate tolerance. Of the three Brazilian native woody species studied, M. caesalpiniaefolia was found to have the highest Pb tolerance and phytostabilisation potential in Pb-contaminated soils.

As moléculas orgânicas podem ser a principal entrada de nitrogênio para plantas em ambientes onde as fontes inorgânicas de nitrogênio são limitadas, como o ambiente epífitico. Estudos recentes têm mostrado que plantas de Vriesea gigantea, uma bromélia epífita formadora de tanque, possuem alta capacidade de absorver ureia, fazendo dela um excelente modelo para estudar o metabolismo de ureia. Entretanto, os processos de absorção e assimilação de ureia estão pouco caracterizados nessas plantas. Várias aquaporinas de plantas têm mostrado ser capazes de facilitar a difusão de ureia através das membranas. Três genes que codificam para aquaporina foliares, VgPIP1;2, VgPIP1;5 e VgTIP2, recentemente foram clonados a partir de plantas V. gigantea tratadas com ureia, sendo que as expressões de VgPIP1,5 e VgTIP2, foram induzidas por essa fonte nitrogenada. No entanto, não tinha sido testado funcionalmente se, de fato, essas aquaporinas seriam capazes de transportar ureia, amônio ou água através das membranas. Uma vez absorvida, a ureia precisa ser metabolizada. Sugere-se que a assimilação do N ocorra por meio da via GS/GOGAT, com prévia hidrólise da ureia pela enzima urease, fornecendo amônio e CO2. Contudo, nunca se analisou a relevância da urease nesse processo em V. gigantea. Dessa maneira, no presente trabalho o transporte de ureia, amônio e água através de VgPIP1;2, VgPIP1;5 e VgTIP2 foi determinado por meio de ensaios de absorção em ovócitos de Xenopus laevis (água e ureia) e de estudos de complementação em Saccharomyces cerevisiae (NH4+/NH3). Os resultados mostraram que, enquanto VgTIP2 facilita o transporte de água quando expresso isoladamente em ovócitos, VgPIP1;2 e VgPIP1;5 precisaram de ser co-expressos com aquaporinas do tipo PIP2 para serem corretamente transportadas para a membrana plasmática e atuem como canais de água. Além disso, VgTIP2 foi a única aquaporina capaz de facilitar a difusão de ureia através das membranas, enquanto que VgPIP1;2 parece ser capaz de transportar NH4+/NH3. Adicionalmente, a relevância da urease no processo de assimilação de ureia foi analisada por meio do perfil isotópico dos aminoácidos em plantas de V. gigantea tratadas com um inibidor da urease (cloranil) antes de fornecer ureia duplamente marcada com C13 e N15. Os experimentos foram conduzidos em plantas nas fases ontogenéticas, atmosférica e adulta-tanque devido a existência de diferenças metabólicas e morfológicas. Os resultados sugeriram que a atividade da urease é um passo limitante na conversão do N da ureia em amônio para sua assimilação. Adicionalmente, foi visto que a diminuição na atividade da urease afeta principalmente a formação de glutamina (Gln) em plantas atmosféricas, enquanto que em plantas adultas-tanque a transaminação é o principal processo prejudicado. A diferença de assimilação de ureia entre as fases ontogenéticas podem ser consequência de diferenças morfológicas associadas com estratégias para captar nutrientes. Além disso, apesar da diminuição da atividade da urease pela ação do inibidor, processos de assimilação direta (sem prévia hidrólise da ureia anterior) em plantas V. gigantea parecem improváveis de acontecer Organic molecules can be the main input of nitrogen for plants in environments where inorganic nitrogen sources are limited, such as the epiphytic habitat. Recent studies have shown a high capacity of Vriesea gigantean, an epiphytic tank-forming bromeliad, to absorb urea by their leaves, making this bromeliad an excellent model to study urea metabolism. Nevertheless, urea uptake and assimilation processes are little characterized in these plants. Several plant aquaporins from different species are able to facilitate the diffusion of urea through the membranes. Three foliar aquaporin genes, VgPIP1;2, VgPIP1;5 and VgTIP2, have been recently cloned from urea-treated V. gigantea plants. The expression of VgPIP1;5 and VgTIP2 was specifically up-regulated by urea in the basal part of the leaves. Nevertheless, it had not been tested whether these aquaporins were in fact capable of facilitating the membrane diffusion of either urea, ammonium or water. Moreover, it was suggested that after urea absorption, this organic N compound is hydrolyzed by the urease enzyme into CO2 and NH4+ prior to NH4+ assimilation by the GS/GOGAT pathway. In the present project, urea, NH4+/NH3 and water diffusion through VgPIP1;2, VgPIP1;5 and VgTIP2 were determined by uptake studies in Xenopus laevis oocytes (urea and water)and complementation assay in Saccharomyces cerevisiae (NH4+/NH3). The results showed that while VgTIP2 facilitates water transport when expressed alone in oocytes, VgPIP1;2 and VgPIP1;5 needed to be co-expressed with a PIP2 aquaporin to be targeted to the plasma membrane and act as water channels. Moreover, VgTIP2 was the only aquaporin able to facilitate the diffusion of urea through the membrane, while VgPIP1;2 seems to be capable of transporting NH4+/NH3. Additionally, the urease relevance in the urea assimilation process was investigated through the analysis of the amino acid profile in V. gigantea plants kept under a urease inhibitor (chloranil) and supplied with labeled [13C]-[ 15N]2-urea. The experiments were conducted in atmosphheric and adult-tank ontogenetic stages of V. gigantea due to their metabolic and morphological differences. The results suggested that urease activity may be a limiting step in the conversion of N from urea to ammonium. Moreover, decreases in urease activity by chloranil impared the first steps in N assimilation, droping the pool of glutamine (Gln) in atmospheric plants. In adult-tank plants the transamination appeared to be adversely affected. Those differences in urea assimilation might be due to differences in the morphology and the nutrient capture strategies of the ontogenetic phases. Finally, direct urea assimilation process (without previous urea hydrolysis) in V. gigantea plants seems unlikely to occur