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A transcriptome analysis of the Populus alba cambial region was performed with the aim of elucidating the gene network underlying the response to water deficit within the cambium and differentiating derivative cambial cells. Water stress was induced in 1-year-old P. alba plants by withholding water for 9 days. At that time, leaf predawn water potential fell to -0.8 MPa, resulting in a significant reduction in stomatal conductance, CO(2) assimilation and a consistent increment of stem shrinkage. These effects were almost fully reversed by re-hydration. The water deficit resulted in changes in gene expression that affected several functional categories, such as protein metabolism, cell wall metabolism, stress response, transporters and transcriptional regulation. The function of up- and down-regulated genes is discussed considering the physiological response of the plants to water deficit.

The involvement of metallothioneins (MTs) in response to plant water stress and recovery was assessed by analyzing gene expression in leaves and in the cambial zone of white poplar. One-year-old plants were submitted to two different watering regimes: irrigation was withheld for 9d and then resumed until day 17, or soil moisture was maintained to field capacity by irrigation during the experiment. Changes in leaves and stem water relations, gas exchange and CO(2) assimilation were recorded. The expression profiles of MT genes were analyzed in developing leaves and the cambial zone at maximum stress levels and after recovery and compared with the watered controls. Whole-plant water relations were significantly affected by water deprivation, though a complete recovery of plant water status was reached after resumption of watering. Withholding irrigation resulted in a significant decrease of leaf turgor potential and relative water content without a significant increase of the osmotic potential at full turgor. Similarly, stem water content decreased, leading to a marked increase of stem shrinkage, confirming that mild water stress affected primarily tissue water status. Following water depletion, the transcript analysis of MT genes revealed increased expression of type 3a and 3b MT genes in cambial tissues, and particularly in leaves. After water resumption, transcription decreased, suggesting that the changes in gene expression were related to water deficit. The results indicate that in leaves and, for the first time, in the cambial zone, type 3 MTs respond in a specific manner to changes in water status. These results are consistent with the regulatory cis-elements present in the 5' flanking region of type 3 MT genes.

O presente trabalho constitui uma análise sobre um importante instrumento de defesa contra as práticas desleais de comércio: a investigação de origem não preferencial ponderando a importância e avaliando os benefícios para o comércio exterior brasileiro de coibir as importações com falsa declaração de origem. Nesse contexto, faz-se uma verificação das normas de origem, destacando-se a relevância da aplicação dessas regras para posteriormente discorrer sobre as etapas e a conclusão da investigação de origem não preferencial. Mas esse mecanismo tem uma natureza contraditória, pois da mesma forma que contribui para o fortalecimento das relações comerciais entre diferentes países, pode de alguma forma atentar contra o caráter multilateral e o princípio da não discriminação previsto no GATT. Para contextualizar, faz-se um breve histórico da formação do atual Sistema Multilateral de Comércio. Desta forma, o intuito é mostrar por meio de um caso prático, os passos de uma investigação de origem, destacando os benefícios desse instrumento para a indústria brasileira, as práticas de gestão em decorrência do resultado da investigação e também as falhas que podem ocorrer durante o processo. A pesquisa conclui que a investigação de origem pode ser considerada como um mecanismo de defesa comercial demonstrando que o objetivo foi alcançado., The present work aimed at analyzing a significant defense instrument against unfair trade practices: non-preferential rules of origin, weighing the importance and assessing the benefits when Brazilian foreign trade to curb imports with an alleged false declaration of origin. In this context, verification procedures of the rules of origin must be carried out, highlighting the importance of applying these rules to subsequently discuss each one of the steps and the conclusion of the investigation on nonpreferential origin rules. But this mechanism has an adversarial character, since it contributes to the strengthening of trade relations between countries but, at the same time, it can somehow undermine the multilateral profile and the principle of nondiscrimination laid down in GATT. In order to place this debate in a context, a brief historical overview of the formation of the current multilateral trading system was also provided. Therefore, the main goal of this research was to show, through a case study, all the steps involved in a process of origin investigation, emphasizing the benefits of this instrument for Brazilian industry and also possible failures that may occur., Orientação: António Augusto Teixeira da Costa

The expression of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) in water deficit conditions was investigated in poplar cambium and leaf to study the regulation of the different members of these multigene families during water stress. The daily stem radial growth was used to evaluate plant water status at the whole-tree level and after 22 days of reduced irrigation regime, a decline of radial growth of 37% was observed. The expression patterns of the genes were analysed by means of relative quantitative RT-PCR. Water deficiency affected significantly the expression of the peroxisomal APX and mitochondrial MnSODs genes in the cambium, evidencing the crucial role of these subcellular compartments for the redox homeostasis in this tissue. To our knowledge, this is the first report of a transcriptional analysis of multiple SOD, CAT and APX genes in poplar cambium in response to water deficit.