Markku Keinänen

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Short, high-concentration peaks of the atmospheric pollutant ozone (O(3)) cause the formation of cell death lesions on the leaves of sensitive plants. Numerous similarities between the plant responses to O(3) and pathogens suggest that O(3) triggers hypersensitive response-like programmed cell death (PCD). We examined O(3) and superoxide-induced cell death(More)
The fatty acid hydroperoxide (HP) substrates required for the biosynthesis of jasmonic acid (JA) and green leaf volatiles (GLVs) are supplied by separate lipoxygenases (LOX). We silenced the expression of two genes downstream of the LOX: allene oxide synthase (AOS) and HP lyase (HPL) by antisense expression of endogenous genes (NaAOS, NaHPL) in Nicotiana(More)
 Phenolics and terpenoids characteristic for silver birch (Betula pendula Roth) were screened in current-growth twigs of seedlings (1-growing-season-old individuals) and current-growth twigs of saplings (3 to 5-year-old individuals) of several birch species. Seedlings were grown in a greenhouse for 1 growing season. Saplings were field cultivated or(More)
We have used genotypic variation in birch (Betula pendula Roth) to investigate the roles of ozone (O(3))-induced ethylene (ET), jasmonic acid, and salicylic acid in the regulation of tissue tolerance to O(3). Of these hormones, ET evolution correlated best with O(3)-induced cell death. Disruption of ET perception by transformation of birch with the dominant(More)
The role of ethylene (ET) signaling in the responses of two hybrid aspen (Populus tremula L. x P. tremuloides Michx.) clones to chronic ozone (O(3); 75 nL L(-1)) was investigated. The hormonal responses differed between the clones; the O(3)-sensitive clone 51 had higher ET evolution than the tolerant clone 200 during the exposure, whereas the free salicylic(More)
Chloroplast NADPH-thioredoxin reductase (NTRC) belongs to the thioredoxin systems that control crucial metabolic and regulatory pathways in plants. Here, by characterization of T-DNA insertion lines of NTRC gene, we uncover a novel connection between chloroplast thiol redox regulation and the control of photoperiodic growth in Arabidopsis (Arabidopsis(More)
Reactive oxygen species (ROS) are ubiquitous signaling molecules in plant stress and development. To gain further insight into the plant transcriptional response to apoplastic ROS, the phytotoxic atmospheric pollutant ozone was used as a model ROS inducer in Arabidopsis (Arabidopsis thaliana) and gene expression was analyzed with microarrays. In contrast to(More)
The effect of elevated atmospheric CO2 and temperature on resource allocation and secondary chemistry of white birch (Betula pendula Roth) under a non-limiting nutrient and water supply was investigated. Birch seedlings were grown in closed-top chambers exposed to ambient CO2 and temperature, elevated atmospheric CO2 (700 ppm), elevated temperature (2°C(More)
Ultraviolet (UV) radiation is an important environmental factor for plant communities; however, plant responses to solar UV are not fully understood. Here, we report differential effects of solar UV-A and UV-B radiation on the expression of flavonoid pathway genes and phenolic accumulation in leaves of Betula pendula Roth (silver birch) seedlings grown(More)
The phylogenetic relationships within the genus Betula (Betulaceae) were investigated using a part of the nuclear ADH gene and DNA sequences of the chloroplast matK gene with parts of its flanking regions. Two well-supported phylogenetic groups could be identified in the chloroplast DNA sequence: one containing the three American species B. lenta, B.(More)