The sieve element occlusion gene family in dicotyledonous plants

Sieve element occlusion (SEO) genes encoding forisome subunits have been identified in Medicago truncatula and other legumes. Forisomes are structural phloem proteins uniquely found in Fabaceae sieve elements. They undergo a reversible conformational change after wounding, from a condensed to a dispersed state, thereby blocking sieve tube translocation and preventing the loss of photoassimilates. Recently, we identified SEO genes in several non-Fabaceae plants (lacking forisomes) and concluded that they most probably encode conventional non-forisome P-proteins. Molecular and phylogenetic analysis of the SEO gene family has identified domains that are characteristic for SEO proteins. Here, we extended our phylogenetic analysis by including additional SEO genes from several diverse species based on recently published genomic data. Our results strengthen the original assumption that SEO genes seem to be widespread in dicotyledonous angiosperms, and further underline the divergent evolution of SEO genes within the Fabaceae.Key words: forisome, P-protein, sieve element occlusion, phloem, wound sealing, gene family, Fabacea     

Metabolism of 3-chloro-, 4-chloro-, and 3,5-dichlorobenzoate by a pseudomonad.

Pseudomonas sp. WR912 was isolated by continuous enrichment in three steps with 3-chloro-, 4-chloro-, and finally 3,5-dichlorobenzoate as sole source of carbon and energy. The doubling times of the pure culture with these growth substrates were 2.6, 3.3, and 5.2 h, respectively. Stoichiometric amounts of chloride were eliminated during growth. Oxygen uptake rates with chlorinated benzoates revealed low stereospecificity of the initial benzoate 1,2-dioxygenation. Dihydrodi-hydroxybenzoate dehydrogenase, catechol 1,2-dixoygenase, and muconate cycloisomerase activities were found in cell-free extracts. The ortho cleavage activity for catechols appeared to involve induction of isoenzymes with different stereospecificity towards chlorocatechols. A catabolic pathway for chlorocatechols was proposed on the basis of similarity to chlorophenoxyacetate catabolism, and cometabolism of 3,5-dimethylbenzoate by chlorobenzoate-induced cells yielded 2,5-dihydro-2,4-dimethyl-5-oxo-furan-2-acetic acid.     

Microbial Transport, Survival, and Succession in a Sequence of Buried Sediments

Abstract Two chronosequences of unsaturated, buried loess sediments, ranging in age from <10,000 years to >1 million years, were investigated to reconstruct patterns of microbial ecological succession that have occurred since sediment burial. The relative importance of microbial transport and survival to succession was inferred from sediment ages, porewater ages, patterns of abundance (measured by direct counts, counts of culturable cells, and total phospholipid fatty acids), activities (measured by radiotracer and enzyme assays), and community composition (measured by phospholipid fatty acid patterns and Biolog substrate usage). Core samples were collected at two sites 40 km apart in the Palouse region of eastern Washington State, near the towns of Washtucna and Winona. The Washtucna site was flooded multiple times during the Pleistocene by glacial outburst floods; the Winona site elevation is above flood stage. Sediments at the Washtucna site were collected from near surface to 14.9 m depth, where the sediment age was approximately 250 ka and the porewater age was 3700 years; sample intervals at the Winona site ranged from near surface to 38 m (sediment age: approximately 1 Ma; porewater age: 1200 years). Microbial abundance and activities declined with depth at both sites; however, even the deepest, oldest sediments showed evidence of viable microorganisms. Same-age sediments had equal quantities of microorganisms, but different community types. Differences in community makeup between the two sites can be attributed to differences in groundwater recharge and paleoflooding. Estimates of the microbial community age can be constrained by porewater and sediment ages. In the shallower sediments (<9 m at Washtucna, <12 m at Winona), the microbial communities are likely similar in age to the groundwater; thus, microbial succession has been influenced by recent transport of microorganisms from the surface. In the deeper sediments, the populations may be considerably older than the porewater ages, since microbial transport is severely restricted in unsaturated sediments. This is particularly true at the Winona site, which was never flooded.     

Total degradation of various chlorobiphenyls by cocultures and in vivo constructed hybrid pseudomonads

Cocultures consisting of strains converting chlorobiphenyls to the respective benzoates or catechols and of chlorobenzoate degraders were investigated for the mineralization of chlorobiphenyls. Stable mixed cultures were obtained with 4-chlorobiphenyl, while those with 2-chloro- or 3-chlorobiphenyl were found to be unstable and released only low yields of chloride. When both sets of enzyme sequences were combined in one organism, Pseudomonas cepacia strain JH230, by conjugative transfer of genes of the biphenyl degradation sequence, the total degradation of 2-chloro-, 3-chloro-, 4-chloro-, 2,4-dichloro-, and 3,5-dichlorobiphenyl was achieved.     

Biocontrol of strawberry fruit infected by Botrytis cinerea: Effects on the microbial communities on fruit assessed by next‐generation sequencing

Fruit grey mould, caused by the fungus Botrytis cinerea, is known to be a harmful disease of strawberry at postharvest stage. However, effects of an application of biological control agents (BCAs) on strawberry fruit in terms of shift in the microbial community are still unknown. The present research aimed to investigate the effects of an application of BCAs on postharvest microbial populations present on strawberry fruits. Strawberry plants were sprayed with three kinds of BCA, RhizoVital 42 fl. (Bacillus amyloliquefaciens FZB42), Trianum‐P (Trichoderma harzianum T22) and Naturalis (Beauveria bassiana ATCC 74040), targeting Botrytis cinerea fungus. Control plots were composed of water and fungicide treatments. Microbial communities (bacteria and fungi) were analysed via next‐generation sequencing on an Illumina MiSeq. Analysis of 16S RNA and ITS rRNA sequences indicated that the BCAs application modified both bacterial and fungal community compositions and diversity. An application of two BCAs together had more effects on microbial community composition than a single application. These results suggest that BCAs can modify bacterial and fungal community composition and diversity on strawberry fruits, which may consequently improve the efficiency and establishment of these products on control of postharvest diseases of fruits, such as grey mould.     

Microbial degradation of chloroaromatics: use of the meta-cleavage pathway for mineralization of chlorobenzene.

Pseudomonas putida GJ31 is able to simultaneously grow on toluene and chlorobenzene. When cultures of this strain were inhibited with 3-fluorocatechol while growing on toluene or chlorobenzene, 3-methylcatechol or 3-chlorocatechol, respectively, accumulated in the medium. To establish the catabolic routes for these catechols, activities of enzymes of the (modified) ortho- and meta-cleavage pathways were measured in crude extracts of cells of P. putida GJ31 grown on various aromatic substrates, including chlorobenzene. The enzymes of the modified ortho-cleavage pathway were never present, while the enzymes of the meta-cleavage pathway were detected in all cultures. This indicated that chloroaromatics and methylaromatics are both converted via the meta-cleavage pathway. Meta cleavage of 3-chlorocatechol usually leads to the formation of a reactive acylchloride, which inactivates the catechol 2,3-dioxygenase and blocks further degradation of catechols. However, partially purified catechol 2,3-dioxygenase of P. putida GJ31 converted 3-chlorocatechol to 2-hydroxy-cis,cis-muconic acid. Apparently, P. putida GJ31 has a meta-cleavage enzyme which is resistant to inactivation by the acylchloride, providing this strain with the exceptional ability to degrade both toluene and chlorobenzene via the meta-cleavage pathway.     

Epstein-Barr Virus Infection and Altered Control of Apoptotic Pathways in Posttransplant Lymphoproliferative Disorders

Posttransplant lymphoproliferative disorders (PTLD) represent a spectrum of lymphoid diseases complicating the clinical course of transplant recipients. Most PTLD are Epstein-Barr virus (EBV) associated with viral latency type III. Several in vitro studies have revealed an interaction between EBV latency proteins and molecules of the apoptosis pathway. Data on human PTLD regarding an association between Bcl-2 family proteins and EBV are scarce. We analyzed 60 primary PTLD for expression of 8 anti- (Bcl-2, Bcl-XL, and Mcl-1) and proapoptotic proteins (Bak and Bax), the so-called BH3-only proteins (Bad, Bid, Bim, and Puma), as well as the apoptosis effector cleaved PARP by immunohistochemistry. Bim and cleaved PARP were both significantly (p = 0.001 and p = 5.251e-6) downregulated in EBV-positive compared to EBV-negative PTLD [Bim: 6/40 (15%), cleaved PARP: 10/43 (23%), vs. Bim: 13/16 (81%), cleaved PARP: 12/17 (71%)]. Additionally, we observed a tendency toward increased Bcl-2 protein expression (p = 0.24) in EBV-positive PTLD. Hence, we provide evidence of a distinct regulation of Bcl-2 family proteins in EBV-positive versus negative PTLD. The low-expression pattern of the proapoptotic proteins Bim and cleaved PARP together with the high-expression pattern of the antiapoptotic protein Bcl-2 by trend in EBV-positive tumor cells suggests disruption of the apoptotic pathway by EBV in PTLD, promoting survival signals in the host cells.     

Genetic analysis of Cydia pomonella (Lepidoptera: Tortricidae) populations with different levels of sensitivity towards the Cydia pomonella granulovirus (CpGV)

Microsatellite (simple sequence repeats, SSR) and mitochondrial DNA markers were used to assess the structure of European codling moth populations showing different levels of susceptibility towards one of the most important biocontrol agents used in apple production, the Cydia pomonella granulovirus CpGV-M. In 638 C. pomonella individuals from 33 different populations a total of 92 different alleles were scored using six SSR loci. The global estimate of genetic differentiation for all 33 populations was not significantly different from zero, thus indicating a lack of genetic differentiation. AMOVA analysis revealed a very weak but significant variance among C. pomonella populations from different geographic regions, however, no significant variation was evident between CpGV-M resistant or susceptible C. pomonella populations. Sequence analysis of a fragment of the cytochrome oxidase subunit 1 in eight C. pomonella populations resulted in 27 haplotypes, which were grouped in two distinct clusters. Again, no genetic differentiation between CpGV-M resistant and susceptible codling moth populations was detectable. In addition, Structure analysis using microsatellites and association tests with mtDNA haplotypes found neither population-level nor individual correlations associated with CpGV-M resistance. Accordingly, this lack of population structure does not allow discriminating between one or several, separate origins of CpGV-M resistance.