SUMMARYThe central structure of the symbiotic association between plants and arbuscular mycorrhizal (AM) fungi is the fungal arbuscule that delivers minerals to the plant. Our earlier transcriptome analyses identified two half-size ABCG transporters that displayed enhanced mRNA levels in mycorrhizal roots. We now show specific transcript accumulation in arbusculated cells of both genes during symbiosis. Presently, arbuscule-relevant factors from monocotyledons have not been reported. Mutation of either of the Oryza sativa (rice) ABCG transporters blocked arbuscule growth of different AM fungi at a small and stunted stage, recapitulating the phenotype of Medicago truncatula stunted arbuscule 1 and 2 (str1 and str2) mutants that are deficient in homologous ABCG genes. This phenotypic resemblance and phylogenetic analysis suggest functional conservation of STR1 and STR2 across the angiosperms. Malnutrition of the fungus underlying limited arbuscular growth was excluded by the absence of complementation of the str1 phenotype by wild-type nurse plants. Furthermore, plant AM signaling was found to be intact, as arbuscule-induced marker transcript accumulation was not affected in str1 mutants. Strigolactones have previously been hypothesized to operate as intracellular hyphal branching signals and possible substrates of STR1 and STR2. However, full arbuscule development in the strigolactone biosynthesis mutants d10 and d17 suggested strigolactones to be unlikely substrates of STR1/STR2. Interestingly, rice STR1 is associated with a cis-natural antisense transcript (antiSTR1). Analogous to STR1 and STR2, at the root cortex level, the antiSTR1 transcript is specifically detected in arbusculated cells, suggesting unexpected modes of STR1 regulation in rice.
Pseudomonas fluorescens CHA0 is a root-associated biocontrol agent that suppresses soil-borne fungal diseases of crops. Remarkably, the pseudomonad is also endowed with systemic and oral activity against pest insects which depends on the production of the insecticidal Fit toxin. The toxin gene (fitD) is part of a virulence cassette encoding three regulators (FitF, FitG, FitH) and a type I secretion system (FitABC-E). Immunoassays with a toxin-specific antibody and transcriptional analyses involving fitG and fitH deletion and overexpression mutants identified LysR family regulator FitG and response regulator FitH as activator and repressor, respectively, of Fit toxin and transporter expression. To visualize and quantify toxin expression in single live cells by fluorescence microscopy, we developed reporters which in lieu of the native toxin protein express a fusion of the Fit toxin with red fluorescent mCherry. In a wild-type background, expression of the mCherry-tagged Fit toxin was activated at high levels in insect hosts, i.e. when needed, yet not on plant roots or in batch culture. By contrast, a derepressed fitH mutant expressed the toxin in all conditions. P. fluorescens hence can actively induce insect toxin production in response to the host environment, and FitH and FitG are key regulators in this mechanism.
The aim of this paper is to establish the interaction of phenotypical variations, components of yield for the widest spread wine varieties and external factors of the Danube region in the central Serbia. The number of fruitful buds per vine for twenty-one varieties was the same, whereas the yield and the components of the yield were different. The growing season, from bud burst to full ripening of the grapevine and the sum of active temperatures for the same period, were of crucial importance. In the factor analysis, three factors have been singled out: the first factor couples the mean air temperature; the second factor delineates the values according to genotype characteristics, sugar content and acids in the must, and the third factor indicates that bunch weight had the major effect on the yield of grapes. By the application of bunch analysis, a hierarchy tree was formed to include the four groups of varieties. The most numerous group, consisting of 18 varieties, is characterized by top quality grapes (21.5% sugar content), medium yield (1.52 kg/m2) and a proportional relation of total acids (7.5 g/l) and this is achieved during the middle of the ripening period
Clone and sanitary selection of the grapevine has a fundamental importance in improving the quality and the quantity of the grape production in Serbia. In order to preserve the varieties of the old vineyards, the clone and sanitary selection has begun in 2006 in the South Eastern Serbia vineyard areas, 1048 grapevine plants have been examined in three distant vineyards and 60 grapevine plants have been separated that deserved attention based on their production characteristics. The selected plants have been tested serologically, with the ELISA method, to the presence of 4 grapevine viruses: Grapevine leaf roll-associated virus 1, Grapevine leaf roll-associated virus 2 and Grapevine leaf roll-associated virus 3 (GLRaV- 1, GLRaV-2 and GLRaV-3), and grapevine fun leaf virus- GFLV. The infection level of the selected plants was between 10.5% (vineyard III) and 22.2% (vineyard II). We eliminated the infected plants among the selected ones and analyzed only the healthy ones in the 2008. Various potential variety clones have been selected for Prokupac, Pamid, Dimyat, Sauvignon blanc, Rosaki, Chasselas, Semillon, Detier de Bayreuth and Riesling. In 2008 we have repeated the same procedure we did in 2006 but in a different region - the Eastern Serbia area on the autochthonous variety of Muscat des roses noir on 400 grapevine plants 40 potential clones have been selected. The goal of this paper was check out the health status to preserve the autochthonous and introduced varieties of the eastern and south eastern region and to renew the vineyards it’s grown in. It was necessary to go on following the selected candidate - clones for other viruses based on EPPO PM 4/1-26 certification scheme in order to identify the virus-free clones to multiply, conserve and maintain in the collection growing areas
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