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It has been suggested that thiol compounds such as glutathione (GSH) and phytochelatin (PC) contribute to arsenic (As) tolerance mechanisms in higher plant. In contrast, the role of thiol compounds in As tolerance and hyperaccumulation in Pteris vittata, an As hyperaccumulator fern, has not been well demonstrated so far. The purpose of this study was to elucidate that role. Gel-filtration chromatography showed that fronds of P. vittata contained high-molecular-weight As compounds containing thiol compounds. Localization of As showed similar trends to that of thiol compounds, increasing with getting higher in position of pinna. Besides, the molar ratio of thiol to As was nearly equal to the ideal molar ratio of As-thiol complexes. These results suggest that As makes complex with thiol compounds in fronds of P. vittata. When comparing P. vittata with Nephrolepis exaltata, an As nonaccumulator fern, As-induced enhancement of thiol synthesis was observed only in P. vittata. The enhancement of thiol synthesis was induced directly by As, not indirectly by As-mediated oxidative stress. γ-glutamylcysteine (γEC) synthetase is a key enzyme for the synthesis of GSH and PC. Two putative genes of γEC synthetase, PvECS1 and PvECS2, were found in P. vittata. Expression of PvECS2 in shoots increased at 48 h after the onset of As exposure, almost corresponding to the increase in concentrations of γEC and GSH. Moreover, As accumulation in shoots began just before these increases. Thus, this study strongly suggests the contribution of thiol compounds to As tolerance in P. vittata.

Rhodotorula glutinis IFO1125 was found to acquire increased aluminium (AI) resistance from 50 [micro]M to more than 5 mM by repetitive culturing with stepwise increases in AI concentration at pH 4.0. To investigate the mechanism underlying this novel phenomenon, wild-type and AI-resistant cells were compared. Neither cell type accumulated the free form of AI ([AI.sup.3+]) added to the medium. Transmission electron microscopic analyses revealed a greater number of mitochondria in resistant cells. The formation of small mitochondria with simplified cristae structures was observed in the wild-type strain grown in the presence of AI and in resistant cells grown in the absence of AI. Addition of AI to cells resulted in high mitochondrial membrane potential and concomitant generation of reactive oxygen species (ROS). Exposure to AI also resulted in elevated levels of oxidized proteins and oxidized lipids. Addition of the antioxidants [alpha]-tocopherol and ascorbic acid alleviated the AI toxicity, suggesting that ROS generation is the main cause of AI toxicity. Differential display analysis indicated upregulation of mitochondrial genes in the resistant cells. Resistant cells were found to have 2.5- to 3-fold more mitochondrial DNA (mtDNA) than the wild-type strain. Analysis of tricarboxylic acid cycle and respiratory-chain enzyme activities in wild-type and resistant cells revealed significantly reduced cytochrome c oxidase activity and resultant high ROS production in the latter cells. Taken together, these data suggest that the adaptive increased resistance to AI stress in resistant cells resulted from an increased number of mitochondria and increased mtDNA content, as a compensatory response to reduced respiratory activity caused by a deficiency in complex IV function.

Focuses on sex pheromone and related compounds in the Ishigaki and Okinawa strains of the tussock moth Orgyia postica (Walker). Discovery of two distinct electroantennographycally active components, A and B, and a weakly active component C in a solvent extract from virgin females of the Ishigaki strain of the tussock moth; Finding of components A, B, and C in the extract of the females at 4.0, 0.5, and 4.0 ng/female respectively; Confirmation that the attractant pheromone of O. postica of the Ishigaki strain is also (11S,12S)-1; Discussion of the attractiveness of the components to the males on both Japanese islands in the context of the activity and possible evolution of pheromonal polymorphism in the species.

The article presents a simple analytical method for the quantification of cyanamide in plants. It further analyzes the cyanamide contents of the leaves, stems, cotyledons and roots of young seedlings of V. villosa and of the leaves of other Vicia species, Lens culinaris and Robinia pseudoacacia. It reports three advantages of this method over traditional ones which include requirement of less plant material, stable mass chromatogram and reduced risk of enzymatic activity.

To establish a rapid high-throughput evaluation system for the enhanced plant growth-inhibitory activity caused by modifications of cis-cinnamic acid's (cis-CA's) chemical structure, a DNA microarray assay was used to analyze the changes in early gene responses of Arabidopsis thaliana seedlings. After a 6-hr exposure to (Z)-3-(3-iodophenyl)acrylic acid, we observed an upregulation in three classes of early auxin-responsive genes, which was similar to the transcriptional response to indole-3-acetic acid (IAA), together with an upregulation of the genes related to environmental stress and toxin detoxification responses. Gene responses to 2-(3,4-dihydronaphthalen-1-yl)acetic acid were similar to those to IAA. In contrast, fewer genes were upregulated in response to its double-bond isomer, (Z)-2-[3,4-dihydronaphthalen-1(2H)-ylidene]acetic acid, than to cis-CA. DNA microarray data suggest that the structurally different cis-CA analogues trigger diverse gene responses. [ABSTRACT FROM AUTHOR]