No abstract

Most land plants live in close contact with beneficial soil microbes: the majority of land plant species establish symbiosis with arbuscular mycorrhizal fungi, while most legumes, the third largest plant family, can form a symbiosis with nitrogen-fixing rhizobia. These microbes contribute to plant nutrition via endosymbiotic processes that require modulating the expression and function of plant transporter systems. The efficient contribution of these symbionts involves precisely controlled integration of transport, which is enabled by the adaptability and plasticity of their transporters. Advances in our understanding of these systems, driven by functional genomics research, are rapidly filling the gap in knowledge about plant membrane transport involved in these plant-microbe interactions. In this review, we synthesize recent findings associated with different stages of these symbioses, from the pre-symbiotic stage to nutrient exchange, and describe the role of host transport systems in both mycorrhizal and legume-rhizobia symbioses.

Numerous studies suggest a relevant role of cytokinin (CK) distribution in shaping of plant morphology upon changing environment. Nonetheless, our knowledge about an involvement of short-distance CK translocation in root mineral nutrition is still scarce and specific role of CK transporters in root morphology has yet to be established. Revealing the molecular identity of CK transporters is thereby crucial for better understanding of root plasticity during soil fertility, as well as more frequently encountered plant nutrients deficiencies. In this work, we identified and characterized the Medicago truncatula full-size ATP-binding cassette (ABC) transporter belonging to the G subfamily, namely MtABCG40 as a CK importer. Its expression is root-specific and is induced by nitrogen deprivation and CKs. Our analyses indicate that MtABCG40 has a negative impact on lateral root density through decreased lateral root initiation and enhancement of primary root elongation. Moreover, in line with postulated resemblance to lateral roots, we also observed an inhibitory influence of this transporter on nodule number. Our results suggest that MtABCG40 action affects CK signaling which impacts on the cellular response to auxin. We present data that demonstrate a full-size ABCG transporter with a novel function in legumes and CK transport.

Natural environment probes are constantly screened in order to isolate new bacteria strains [1, 2]. Strains isolated from diverse sources are metabolically stronger than the ones collected by us because they must adapt to variable conditions [3, 4]. Thus, indigenous bacteria in the natural environment can produce a wide range of metabolites more effi ciently [1, 5, 6]. Since the biodiesel industry is growing rapidly, simultaneously the amount of crude glycerol obtained is also increasing [7]. One solution to that problem is to utilized crude glycerol and convert it into 1,3-PD as well as organic acids via a microbial method [6, 8-10]. Many researchers have worked on screening the natural environment in search of new strains that can effectively convert crude glycerol to metabolites. However, most of the available literature is all about the same bacteria species: Clostridium butyricum [11], Clostridium pasteurianum [12, 13], Clostridium diolis, Clostridium acetobutylicum, Clostridium butylicum, Clostridium perfi ngens, [14, 15], Klebsiella pneumonia [16], Klebsiella oxytoca [17], Klebsiella aerogenes [16], Lactobacillus reuterii, Lactobacillus buchnerii, Lactobacillus collinoides [18], Enterobacter agglomerans [19], Citrobacter freundii [20-22], Pelobacter carbinolicus, Rautella planticola, and Bacillus welchii [23]. Thus, the screening of the natural environment for the new strains able to convert glycerol into industrial metabolites is a very important