Maurício Antônio Coelho Filho

Analysis of the NAC transcription factor gene family in citrus reveals a novel member involved in multiple abiotic stress responses

The NAC (NAM, ATAF1, -2, and CUC2) gene family encodes a large family of plant-specific transcription factors that play diverse roles in plant development and stress regulation. In this study, we performed a survey of citrus NAC transcription factors in the HarvEST: Citrus database, in which 45 NAC domain-containing proteins were identified and phylogenetically classified into 13 different subfamilies. The results suggest the existence of a structurally diversified family of NAC transcription factors in citrus, which has not been previously characterized. One of these NAC genes, CsNAC1 was found to be a member of the stress-NAC subfamily, whose homologs from other plant species function in pathways of environmental stress response and tolerance, and was further characterized. The CsNAC1 deduced protein was shown to contain the five N-terminal A through E NAC subdomains, a C-terminal region containing three transcriptional activation motifs, and a predicted NAC nuclear localization signal, consistent with its putative role as a NAC transcription factor. In silico analysis indicated that CsNAC1 was primarily expressed in leaves and shoot meristems, and was involved in general stress responses. Quantitative real-time reverse transcription PCR analysis revealed that CsNAC1 was strongly induced by drought stress in leaves of Citrus reshni and Citrus limonia, and also by salt stress, cold, and ABA in leaves and roots of C. reshni. Collectively, these results suggest that CsNAC1 encodes a novel stress-responsive NAC transcription factor that is potentially useful for engineering tolerance to multiple abiotic stresses in citrus.

Evaluating models for estimation of incoming solar radiation in Cruz das Almas, Bahia, Brazil

Em estudos agroambientais a radiacao solar incidente (Rs) e uma das mais importantes variaveis meteorologicas. Na ausencia de dados observados de Rs e possivel estima-los mediante modelos. O objetivo deste estudo foi avaliar modelos baseados na temperatura do ar para estimativa diaria de Rs nas condicoes do Reconcavo Sul da Bahia. Utilizaram-se dados de Rs do periodo de 2004 a 2006, medidos por uma estacao meteorologica automatica pertencente ao INMET, instalada em Cruz das Almas, Bahia. Como etapa preliminar, verificou-se a qualidade dos dados de Rs tomando-se como referencia curvas de radiacao esperada em dias claros. Os seguintes modelos foram avaliados: Hargreaves-Samani para regioes interiores e regioes costeiras, Thornton-Running e o de Weiss. O desempenho de cada metodo foi avaliado atraves dos seguintes indicadores: coeficiente de determincao (R2), razao media (RM), erro absoluto medio (EAM), raiz quadrada do quadrado medio do erro (RQME) e indice de concordância de Wilmott (dW). Os resultados obtidos recomendam o modelo de Hargreaves-Samani para regioes costeiras por apresentar o valor de RM mais proximo de 1 (1,01), menor EAM (2,54 MJ m-2 d-1), menor RQME (3,13 MJ m-2 d-1) e o maior dW (0,90).

Distribuição de raízes de mamoeiro sob diferentes sistemas de irrigação localizada em latossolo de tabuleiros costeiros

O sistema radicular de uma planta e responsavel pela absorcao de agua do solo e deve ser considerado nos calculos da quantidade de agua necessaria para irrigacao. O trabalho teve por objetivo definir a distribuicao do sistema radicular do mamoeiro irrigado por gotejamento e microaspersao em solo de Tabuleiro Costeiro do Reconcavo Baiano. Foram feitas duas trincheiras em diferentes posicoes relativas a duas plantas irrigadas por microaspersao e gotejamento superficial e enterrado a 0,25 m, com as linhas laterais junto a fileira de plantas, com dois gotejadores por planta, cada um a 0,40 m de distância das mesmas. Na microaspersao, usou-se um emissor para duas plantas, entre duas fileiras simples. As amostras de raizes foram extraidas em malha de pontos nessas trincheiras de forma a abranger uma secao completa do sistema radicular. As raizes foram separadas do solo e digitalizadas em computador, sendo as imagens processadas por um aplicativo computacional que estimou o comprimento total e o diâmetro medio das mesmas em cada posicao no perfil. O sistema radicular ocupou maior volume de solo na microaspersao em relacao ao gotejamento, com maior concentracao das raizes na direcao do microaspersor. A profundidade efetiva do sistema radicular do mamoeiro irrigado por gotejamento superficial ou enterrado foi de 0,45 m e na microaspersao variou de 0,15 m na direcao perpendicular a fileira de plantas a 0,35 m entre a planta e o microaspersor.

Survival strategies of citrus rootstocks subjected to drought.

Two citrus rootstocks, Rangpur lime (RL) and Sunki Maravilha mandarin (SM), were analyzed either ungrafted or grafted with their reciprocal graft combinations or with shoot scions of two commercial citrus varieties: Valencia orange (VO) and Tahiti acid lime (TAL). All graft combinations were subjected to distinct watering regimes: well-watered, severe drought and rehydration. Growth and water relation parameters, gas exchange as well as sugar and hormone profiles were determined. Data indicated that RL adopted a dehydration avoidance strategy and maintained growth, whereas SM adopted a dehydration tolerance strategy focused on plant survival. Compared with RL, the leaves and roots of SM exhibited higher concentrations of abscisic acid and salicylic acid, which induced drought tolerance, and accumulation of carbohydrates such as trehalose and raffinose, which are important reactive oxygen species scavengers. SM rootstocks were able to transfer their survival strategy to the grafted shoot scions (RL, VO, TAL). Because of their contrasting survival strategies, RL reached the permanent wilting point more quickly than SM whereas SM recovered from prolonged droughts more efficiently than RL. This is one of the most complete studies of drought tolerance mechanisms in citrus crops and is the first to use reciprocal grafting to clarify scion/rootstock interactions.

Field determintation of young acid lime plants transpiration by the stem heat balance method

ABSTRACT: The stem heat balance method (HBM) measures sap flow (SF) in plants, and can be used toestimate daily transpiration flow. It is a powerful technique for water relations and irrigation field studies,but it has to be tested in species of particular interest. This paper discusses effectiveness of the HBM toestimate transpiration of young acid lime plants ( Citrus latifolia Tan. cv. Tahiti), grafted on citrumelo cv.Swingle ( Poncirus trifoliata Raf. x C. paradisi Macf.), in the field using commercial gauges (model SAG10-ws, Dynamax Inc., Huston), in Piracicaba, State of Sao Paulo, Brazil. SF was correlated to transpirationdetermined by weighing lysimeters and by a steady-state null-balance porometer. The mean ratio betweendaily values of SF and lysimetric measurements was practically unitary, showing a mean difference ofonly 0.05%, being the comparisons of values in periods shorter than 24 hours impaired by effect of windturbulence on lysimeters. The same occurred (mean difference of 0.38%) when SF and canopy transpirationestimated from porometer measurements were compared in 20-min periods, but transpiration tended toexceed SF in periods of higher transpiration and data dispersion was high (r

Comparative study of the protein profiles of Sunki mandarin and Rangpur lime plants in response to water deficit

BackgroundRootstocks play a major role in the tolerance of citrus plants to water deficit by controlling and adjusting the water supply to meet the transpiration demand of the shoots. Alterations in protein abundance in citrus roots are crucial for plant adaptation to water deficit. We performed two-dimensional electrophoresis (2-DE) separation followed by LC/MS/MS to assess the proteome responses of the roots of two citrus rootstocks, Rangpur lime (Citrus limonia Osbeck) and ‘Sunki Maravilha’ (Citrus sunki) mandarin, which show contrasting tolerances to water deficits at the physiological and molecular levels.ResultsChanges in the abundance of 36 and 38 proteins in Rangpur lime and ‘Sunki Maravilha’ mandarin, respectively, were observed via LC/MS/MS in response to water deficit. Multivariate principal component analysis (PCA) of the data revealed major changes in the protein profile of ‘Sunki Maravilha’ in response to water deficit. Additionally, proteomics and systems biology analyses allowed for the general elucidation of the major mechanisms associated with the differential responses to water deficit of both varieties. The defense mechanisms of Rangpur lime included changes in the metabolism of carbohydrates and amino acids as well as in the activation of reactive oxygen species (ROS) detoxification and in the levels of proteins involved in water stress defense. In contrast, the adaptation of ‘Sunki Maravilha’ to stress was aided by the activation of DNA repair and processing proteins.ConclusionsOur study reveals that the levels of a number of proteins involved in various cellular pathways are affected during water deficit in the roots of citrus plants. The results show that acclimatization to water deficit involves specific responses in Rangpur lime and ‘Sunki Maravilha’ mandarin. This study provides insights into the effects of drought on the abundance of proteins in the roots of two varieties of citrus rootstocks. In addition, this work allows for a better understanding of the molecular basis of the response to water deficit in citrus. Further analysis is needed to elucidate the behaviors of the key target proteins involved in this response.

Regulated deficit irrigation and tommy atkins mango orchard productivity under microsprinkling in brazilian semi arid

This study aimed to test controlled levels of water deficiency in soil in mango trees, under microsprinkling irrigation, in semi-arid conditions, and to evaluate its effect in the productivity and fruits quality. The deficits were applied in the phases I, II and III of growth of the fruit, during the productive cycles of the mango tree in 2006 and 2007. The experiment in both cases was arranged in an entirely random design with 10 treatments and 3 repetitions, in the year I, and with 8 treatments and 3 repetitions in the year II. The values of soil water potential, of the treatments submitted to regulated deficit irrigation (RDI), were placed in the range of 0 to -0.011 MPa, showing that the soil humidity varied between the saturation and the field capacity, not characterizing deficit water condition. The average values of stem water potential (Ψstem) varied between -0.90 and -1.74 MPa, evidencing significant effect (p <0.05) just for T1 (without irrigation), T7 and T8 (RDI with 30% of the ETc in the phases II and III, respectively). Through the variance analysis, significant differences were not verified among productivity, number of fruits per plant and size of the fruit, in none of the experiments, what indicates the possibility of reduction of the water use in the irrigation of the mango tree without significant losses of productivity and fruit quality.

Calibration of a capacitance probe in a Paleudult

ABSTRACT: The use of capacitance sensors is one of the methods used to quantitatively measuresoil water contents (θ, m 3 m -3 ). Sensors provide readings at desired depths and time intervals. Acapacitance probe (Diviner 2000) was calibrated for a Rhodic Paleudult from the Piaui State, Brazil. Sixaccess tubes were installed in a 5 × 2 m grid arrangement. Three moisture levels (saturated, moist anddry) were used in two replications. Probe readings and soil samplings to determine θ were made at 0.1m depth intervals down to a depth of 1.0 m. A power calibration equation was developed for eachdepth as well as for the entire soil profile (Root Mean Square Error = 0.014, R 2 = 0.93) for a θ range of0.068 to 0.264 m 3 m -3 . A separate calibration for each depth improves the correlation coefficient andminimizes RMSE. Site-specific calibration improves the accuracy for soil water monitoring.Key words: FDR probe, sensor, irrigation, soil water content CALIBRACAO DE UMA SONDA DE CAPACITÂNCIAEM UM ARGISSOLO

The involvement of gibberellin signalling in the effect of soil resistance to root penetration on leaf elongation and tiller number in wheat

Background and aimsThe concept of root-sourced chemical signals that affect shoot growth in response to drought is widely reported; in particular the role of ABA in regulating stomatal conductance has received much attention. ABA, alone, does not fully explain all the effects of abiotic stresses in the root zone on shoot architecture. An increase in mechanical impedance, which can occur on even relatively modest soil drying, results in reduced root and shoot growth, processes that are potentially regulated by gibberellins (GAs).MethodsIn this study we explored the role of mechanical impedance and exogenous gibberellin (GA3) on root and shoot architecture in wheat seedlings containing the Rht-B1a (tall), Rht-B1b (semi-dwarf) or Rht-B1c (dwarf) alleles in the April-Bearded or Mercia backgrounds. Our experiments were based on the use of the sand culture system which allows the mechanical impedance of the root growth environment to remain constant and independent of water and nutrient availability. We investigated the effects of the application of exogenous GA3 to the root system.ResultsWe found that impeding soil reduced leaf elongation in the tall and semi-dwarf lines, confirming the stunting effect of mechanical impedance which is widely reported. However, leaf elongation in the dwarf lines was not affected by root impedance. Application of GA3 to the roots restored leaf elongation in the tall and semi-dwarf lines growing in impeding soil, with some growth response even in the dwarf line, the longest leaves being obtained when GA was applied to impeded roots of a tall line. Both exogenous GA and root impedance reduced the number of tillers, but there was no interaction with the Rht genotype. The genetic background did not affect the results.ConclusionWe suggest that the GA signalling pathway has an unidentified role in the leaf elongation response to mechanical impedance to root growth.

Desempenho de modelos de calibração de guias de onda acopladas a TDR e a multiplexadores em três tipos de solos

The study aimed at evaluating of calibration models for two kinds of TDR waveguides used with Trase System and TDR 100 equipments linked to the cable tester or the multiplexer. Disturbed samples of three soils were packed in PVC columns and, after soil saturation, two TDR waveguides of three rods with capacitor and with resistor were inserted into the soil columns. The waveguides were connected to two TDR equipments (Trase System and TDR 100), directly to the cable tester or a multiplexer. Soil water content data by gravimetry were collected during the drying process from saturation to values close to the lowest limit of water availability. The readings were performed with TDR probes connected to the cable tester and the multiplexer. A mathematical model was fitted to the bulk dielectric constant (e) and water content data (q) and the performance of five models to obtain q as a function of e was evaluated. Results showed that there was no significant difference between the TDR Trase System capacitor waveguide calibration connected either directly to the water content analyzer or the multiplexer channel. In case of TDR 100 using waveguides with resistor, the calibration has to be performed according to the connection of the waveguide to the water content analyzer or the multiplexer channel. The cubic calibration model performed best, followed by the Roth model, which estimated the values of bulk dielectric constant and water content well with a closer to 0.5 for waveguides with capacitor than for waveguides with resistor.