Tannosomes in the Pericarp Cells of Maloideae (Rosaceae).

Data on the presence of structural units termed tannosomes in the pericarp cells of Maloideae has been obtained for the first time. Tannosomes merge in the vacuoles to form "tannoglobules."

Respiratory flexibility and efficiency are affected by simulated global change in Arctic plants.

Laboratory studies indicate that, in response to environmental conditions, plants modulate respiratory electron partitioning between the 'energy-wasteful' alternative pathway (AP) and the 'energy-conserving' cytochrome pathway (CP). Field data, however, are scarce. Here we investigate how 20-yr field manipulations simulating global change affected electron partitioning in Alaskan Arctic tundra species. We sampled leaves from three dominant tundra species - Betula nana, Eriophorum vaginatum and Rubus chamaemorus - that had been strongly affected by manipulations of soil nutrients, light availability, and warming. We measured foliar dark respiration, in-vivo electron partitioning and alternative oxidase/cytochrome c oxidase concentrations in addition to leaf traits and mitochondrial ultrastructure. Changes in leaf traits and ultrastructure were similar across species. Respiration at 20°C (R(20)) was reduced 15% in all three species grown at elevated temperature, suggesting thermal acclimation of respiration. In Betula, the species with the largest growth response to added nutrients, CP activity increased from 9.4 ± 0.8 to 16.6 ± 1.6 nmol O(2) g(-1) DM s(-1) whereas AP activity was unchanged. The ability of Betula to selectively increase CP activity in response to the environment may contribute to its overall ecological success by increasing respiratory energy efficiency, and thus retaining more carbon for growth.

Temporal sequence of cell wall disassembly events in developing fruits. 1. Analysis of raspberry (Rubus idaeus).

Raspberry fruits were harvested at five developmental stages, from green to red ripe, and the changes in cell wall composition, pectin and hemicellulose solubilization, and depolymerization were analyzed. Fruit softening at intermediate stages of ripening was associated with increased pectin solubilization, which occurred without depolymerization. Arabinose was found to be the most abundant noncellulosic neutral sugar in the cell wall and showed dramatic solubilization late in ripening. No changes in pectin molecular size were observed even at the 100% red stage. Subsequently, as fruit became fully ripe a dramatic depolymerization occurred. In contrast, the hemicellulosic fractions showed no significant changes in content or polymer size during ripening. The paper discusses the sequence of events leading to cell wall disassembly in raspberry fruit.

Adhesion of ectomycorrhizal bacteria to plant cells: an in vitro evidence.

In this study we have investigated, by combining microbial and microscopical techniques, the adhesion ability of bacteria present in Tuber borchii ectomycorrhizosphere. Our data demonstrate that a common pool of bacteria - Pseudomonas, Bacillus, Micrococcus and Moraxella - occurs in all ectomycorrhizal homogenates and that most of these bacteria are able to attach in vitro to plant cells.

In vitro versus in vivo cellulose microfibrils from plant primary wall synthases: structural differences.

Detergent extracts of microsomal fractions from suspension cultured cells of Rubus fruticosus (blackberry) were tested for their ability to synthesize in vitro sizable quantities of cellulose from UDP-glucose. Both Brij 58 and taurocholate were effective and yielded a substantial percentage of cellulose microfibrils together with (1-->3)-beta-d-glucan (callose). The taurocholate extracts, which did not require the addition of Mg(2+), were the most efficient, yielding roughly 20% of cellulose. This cellulose was characterized after callose removal by methylation analysis, electron microscopy, and electron and x-ray synchrotron diffractions; its resistance toward the acid Updegraff reagent was also evaluated. The cellulose microfibrils synthesized in vitro had the same diameter as the endogenous microfibrils isolated from primary cell walls. Both polymers diffracted as cellulose IV(I), a disorganized form of cellulose I. Besides these similarities, the in vitro microfibrils had a higher perfection and crystallinity as well as a better resistance toward the Updegraff reagent. These differences can be attributed to the mode of synthesis of the in vitro microfibrils that are able to grow independently in a neighbor-free environment, as opposed to the cellulose in the parent cell walls where new microfibrils have to interweave with the already laid polymers, with the result of a number of structural defects.

Gene expression analysis of strawberry achene and receptacle maturation using DNA microarrays.

Large-scale, single pass sequencing and parallel gene expression analysis using DNA microarrays were employed for the comprehensive investigation of ripening in strawberry fruit. A total of 1701 cDNA clones (comprising 1100 strawberry ESTs and 601 unsequenced cDNAs) obtained from a strawberry (Fragariaxananassa) ripe fruit cDNA library were displayed on microarrays, and used for monitoring concurrent gene expression in receptacle and achene tissues. Analysis of expression ratios identified 66 out of the 259 (25%) achene-related clones and 80 out of 182 (44%) receptacle-related clones with more than a 4-fold difference in expression between the two tissue types. Half of the achene-associated genes putatively encode proteins with unknown function, and a large number of the remainder were proteins predicted to form part of the signal and regulation cascades related to achene maturation and acquisition of stress and desiccation tolerance. These included phosphatases, protein kinases, 14-3-3 proteins, transcription factors, and others. In the receptacle, key processes and novel genes that could be associated with ripening were identified. Genes putatively encoding proteins related to stress, the cell wall, DNA/RNA/protein, and primary metabolism were highly represented. Apart from providing a global observation on gene expression programmes and metabolic pathways in the developing strawberry, this study has made available a large database and unique information for gene discovery, promoter selection and markers for molecular breeding approaches.