The Baltic Sea is one of the world's largest brackish water basins and is traditionally considered to be species poor. Here, we assessed the diversity of the nanosized eukaryotic microbial wintertime community, using molecular ecological methods based on sequencing of small-subunit ribosomal RNA gene clone libraries. The results demonstrate that a rich community of small eukaryotes inhabits the Baltic Sea ice and water during winter. The community was dominated by alveolates and stramenopiles. Ciliates and cercozoans were the richest groups present, while in contrast to previous studies, diatoms showed a lower richness than expected. Furthermore, fungi and parasitic Syndiniales were present both in the water and in the sea ice. Some of the organisms in the sea-ice community were active, based on the RNA data, but a number of organisms were inactive or remnants from the freezing process. The results demonstrate that the sea-ice communities in the Baltic Sea are highly diverse and that water and ice of diVerent ages include diVerent protistan assemblages. Our study emphasizes the potential loss in biodiversity through diminishing ice cover as a result of climate change.

BackgroundThe Arabidopsis thaliana F-box protein MORE AXILLARY GROWTH2 (MAX2) has previously been characterized for its role in plant development. MAX2 appears essential for the perception of the newly characterized phytohormone strigolactone, a negative regulator of polar auxin transport in Arabidopsis.ResultsA reverse genetic screen for F-box protein mutants altered in their stress responses identified MAX2 as a component of plant defense. Here we show that MAX2 contributes to plant resistance against pathogenic bacteria. Interestingly, max2 mutant plants showed increased susceptibility to the bacterial necrotroph Pectobacterium carotovorum as well as to the hemi-biotroph Pseudomonas syringae but not to the fungal necrotroph Botrytis cinerea. max2 mutant phenotype was associated with constitutively increased stomatal conductance and decreased tolerance to apoplastic ROS but also with alterations in hormonal balance.ConclusionsOur results suggest that MAX2 previously characterized for its role in regulation of polar auxin transport in Arabidopsis, and thus plant development also significantly influences plant disease resistance. We conclude that the increased susceptibility to P. syringae and P. carotovorum is due to increased stomatal conductance in max2 mutants promoting pathogen entry into the plant apoplast. Additional factors contributing to pathogen susceptibility in max2 plants include decreased tolerance to pathogen-triggered apoplastic ROS and alterations in hormonal signaling.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0434-4) contains supplementary material, which is available to authorized users.

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We examined the relationship between root carbohydrates and sprouting efficiency in four hybrid aspen ( Populus tremula × Populus tremuloides ) clones. Our hypothesis was that the interclonal variation in sprouting efficiency is due to the concentration of carbohydrates. In addition to that relationship, we wanted to study seasonal fluctuation of carbohydrates and how the –18 °C storage conditions of stock plants affects the stability of carbohydrate content and thus sprouting ability of roots cuttings. Clones varied in root carbohydrate content, and sucrose showed the greatest variation throughout the year. Sucrose levels were highest in the clone with the highest sprouting efficiency and lowest in the clone with the lowest sprouting efficiency. Carbohydrate concentrations were highest in winter and lowest in early autumn. In general, root cuttings sprouted most efficiently when root carbohydrate levels peaked. Although root cuttings taken from frozen (–18 °C) stock plants sprouted poorly in summer and autumn, they had high and almost constant carbohydrate concentrations throughout the year.