RESUMO
Changes in gene expression form a key component of the molecular mechanisms by which plants adapt and respond to environmental stresses. There is compelling evidence for the role of stimulus-specific Ca(2+) signatures in plant stress responses. However, our understanding of how they orchestrate the differential expression of stress-induced genes remains fragmentary. We have undertaken a global study of changes in the Arabidopsis transcriptome induced by the pollutant ozone in order to establish a robust transcriptional response against which to test the ability of Ca(2+) signatures to encode stimulus-specific transcriptional information. We show that the expression of a set of co-regulated ozone-induced genes is Ca(2+)-dependent and that abolition of the ozone-induced Ca(2+) signature inhibits the induction of these genes by ozone. No induction of this set of ozone-regulated genes was observed in response to H(2)O(2), one of the reactive oxygen species (ROS) generated by ozone, or cold stress, which also generates ROS, both of which stimulate changes in [Ca(2+)](cyt). These data establish unequivocally that the Ca(2+)-dependent changes in gene expression observed in response to ozone are not simply a consequence of an ROS-induced increase in [Ca(2+) ](cyt) per se. The magnitude and temporal dynamics of the ozone, H(2)O(2) , and cold Ca(2+) signatures all differ markedly. This finding is consistent with the hypothesis that stimulus-specific transcriptional information can be encoded in the spatiotemporal dynamics of complex Ca(2+) signals in plants.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/fisiologia , Cálcio/metabolismo , Regulação da Expressão Gênica de Plantas/genética , Ozônio/farmacologia , Transdução de Sinais/fisiologia , Equorina/genética , Apoproteínas/genética , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Arabidopsis/metabolismo , Cálcio/análise , Análise por Conglomerados , Temperatura Baixa , Biologia Computacional , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Redes Reguladoras de Genes/efeitos dos fármacos , Peróxido de Hidrogênio/farmacologia , Análise de Sequência com Séries de Oligonucleotídeos , RNA de Plantas/genética , Proteínas Recombinantes/genética , Plântula/efeitos dos fármacos , Plântula/genética , Plântula/metabolismo , Plântula/fisiologia , Estresse Fisiológico , Fatores de TempoRESUMO
Most agronomic traits of importance, whether physiological (such as nutrient use efficiency) or developmental (such as flowering time), are controlled simultaneously by multiple genes and their interactions with the environment. Here, we show that variation in sulfate content between wild Arabidopsis thaliana accessions Bay-0 and Shahdara is controlled by a major quantitative trait locus that results in a strong interaction with nitrogen availability in the soil. Combining genetic and biochemical results and using a candidate gene approach, we have cloned the underlying gene, showing how a single-amino acid substitution in a key enzyme of the assimilatory sulfate reduction pathway, adenosine 5'-phosphosulfate reductase, is responsible for a decrease in enzyme activity, leading to sulfate accumulation in the plant. This work illustrates the potential of natural variation as a source of new alleles of known genes, which can aid in the study of gene function and metabolic pathway regulation. Our new insights on sulfate assimilation may have an impact on sulfur fertilizer use and stress defense improvement.
Assuntos
Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Arabidopsis/enzimologia , Arabidopsis/genética , Variação Genética , Oxirredutases atuantes sobre Doadores de Grupo Enxofre/química , Oxirredutases atuantes sobre Doadores de Grupo Enxofre/fisiologia , Sulfatos/metabolismo , Proteínas de Arabidopsis/fisiologia , Isoenzimas/química , Isoenzimas/genética , Isoenzimas/fisiologia , Oxirredução , Oxirredutases atuantes sobre Doadores de Grupo Enxofre/genética , Locos de Características QuantitativasRESUMO
Stomatal responses to air pollutants are complex, varying among species and with concentration, environmental conditions and age. In general, short-term exposure to sulphur dioxide (SO2 ) promotes stomatal opening, whereas longer-term exposure can cause partial stomatal closure. By contrast, the effects of oxides of nitrogen (NOx ) are often small or insignificant. The effects of ozone, and oxidative stress, are equally complex. Short-term exposure to ozone stimulates a rapid reduction in stomatal aperture, whilst longer-term exposure causes stomatal responses to become sluggish. The response of stomata to abscisic acid (ABA) has been shown to be slower in plants exposed to a combination of SO2 and NO2 suggesting an adverse effect on guard cell ABA signal transduction. In addition, ozone causes a reduction in stomatal closure under drought conditions. There is an increasing body of evidence to suggest that air pollutants and oxidative stresses can have a marked effect on the Ca2+ homeostasis of guard cells and the intracellular machinery responsible for stomatal movements. Here we discuss the effects of air pollutants on stomatal responses and their possible effects on Ca2+ based signalling in guard cells focusing on the effects of ozone and oxidative stress.
