Constitutively Elevated Salicylic Acid Levels Alter Photosynthesis and Oxidative State but Not Growth in Transgenic Populus

Salicylic acid (SA) has long been implicated in plant responses to oxidative stress. SA overproduction in Arabidopsis thaliana leads to dwarfism, making in planta assessment of SA effects difficult in this model system. We report that transgenic Populus tremula × alba expressing a bacterial SA synthase hyperaccumulated SA and SA conjugates without negative growth consequences. In the absence of stress, endogenously elevated SA elicited widespread metabolic and transcriptional changes that resembled those of wild-type plants exposed to oxidative stress-promoting heat treatments. Potential signaling and oxidative stress markers azelaic and gluconic acids as well as antioxidant chlorogenic acids were strongly coregulated with SA, while soluble sugars and other phenylpropanoids were inversely correlated. Photosynthetic responses to heat were attenuated in SA-overproducing plants. Network analysis identified potential drivers of SA-mediated transcriptome rewiring, including receptor-like kinases and WRKY transcription factors. Orthologs of Arabidopsis SA signaling components NON-EXPRESSOR OF PATHOGENESIS-RELATED GENES1 and thioredoxins were not represented. However, all members of the expanded Populus nucleoredoxin-1 family exhibited increased expression and increased network connectivity in SA-overproducing Populus, suggesting a previously undescribed role in SA-mediated redox regulation. The SA response in Populus involved a reprogramming of carbon uptake and partitioning during stress that is compatible with constitutive chemical defense and sustained growth, contrasting with the SA response in Arabidopsis, which is transient and compromises growth if sustained

Constitutively elevated salicylic acid levels alter photosynthesis and oxidative state but not growth in transgenic Populus

Salicylic acid (SA) has long been implicated in plant responses to oxidative stress. SA overproduction in Arabidopsis thaliana leads to dwarfism, making in planta assessment of SA effects difficult in this model system. We report that transgenic Populus tremula × alba expressing a bacterial SA synthase hyperaccumulated SA and SA conjugates without negative growth consequences. In the absence of stress, endogenously elevated SA elicited widespread metabolic and transcriptional changes that resembled those of wild-type plants exposed to oxidative stress-promoting heat treatments. Potential signaling and oxidative stress markers azelaic and gluconic acids as well as antioxidant chlorogenic acids were strongly coregulated with SA, while soluble sugars and other phenylpropanoids were inversely correlated. Photosynthetic responses to heat were attenuated in SA-overproducing plants. Network analysis identified potential drivers of SA-mediated transcriptome rewiring, including receptor-like kinases and WRKY transcription factors. Orthologs of Arabidopsis SA signaling components NONEXPRESSOR OF PATHOGENESIS-RELATED GENES1 and thioredoxins were not represented. However, all members of the expanded Populus nucleoredoxin-1 family exhibited increased expression and increased network connectivity in SA-overproducing Populus, suggesting a previously undescribed role in SA-mediated redox regulation. The SA response in Populus involved a reprogramming of carbon uptake and partitioning during stress that is compatible with constitutive chemical defense and sustained growth, contrasting with the SA response in Arabidopsis, which is transient and compromises growth if sustained. © 2013 American Society of Plant Biologists. All rights reserved

El ambiente entre representación y ecología - Un estudio de caso en Guatemala, siglo XIX The environment: between representation and ecology - A case study of Guatemala, 19th century

<abstract language="por">A Guatemala - onde a cultura do café assumiu papel relevante - foi alvo de intensa idealização de sua natureza, ao mesmo tempo em que foi exaltada como uma nação essencialmente agrícola. Tais imagens se construíram tanto sobre bases naturais como sobre representa ções sociais e históricas. Muitos estudos apontam a existência de duas macro-regiões homogêneas no seu território. Entretanto, cada uma delas apresenta uma composição ecológica muito mais variada do que se supõe tradicionalmente, o que se configura como um dos principais fatores de compreensão da constituição histórica das regiões de plantio do café naquele país.<br>Guatemala - where the culture of coffee became relevant - was the target of intense idealization of its nature, at the same time that it was exalted as an essentially agricultural nation. Such images were built upon natural bases as well as upon social and historical representations. Many studies point to the existence of two homogeneous macroregions in the territory. However, each one of them presents an ecological composition much more varied than is traditionally supposed, which is one of the main factors for understanding the historical constitution of coffee plantation regions in that country