Transcriptional Changes in Potato Sprouts upon Interaction with Rhizoctonia solani Indicate Pathogen-Induced Interference in the Defence Pathways of Potato.

Rhizoctonia solani is the causer of black scurf disease on potatoes and is responsible for high economical losses in global agriculture. In order to increase the limited knowledge of the plants' molecular response to this pathogen, we inoculated potatoes with R. solani AG3-PT isolate Ben3 and carried out RNA sequencing with total RNA extracted from potato sprouts at three and eight days post inoculation (dpi). In this dual RNA-sequencing experiment, the necrotrophic lifestyle of R. solani AG3-PT during early phases of interaction with its host has already been characterised. Here the potato plants' comprehensive transcriptional response to inoculation with R. solani AG3 was evaluated for the first time based on significantly different expressed plant genes extracted with DESeq analysis. Overall, 1640 genes were differentially expressed, comparing control (-Rs) and with R. solani AG3-PT isolate Ben3 inoculated plants (+Rs). Genes involved in the production of anti-fungal proteins and secondary metabolites with antifungal properties were significantly up regulated upon inoculation with R. solani. Gene ontology (GO) terms involved in the regulation of hormone levels (i.e., ethylene (ET) and jasmonic acid (JA) at 3 dpi and salicylic acid (SA) and JA response pathways at 8 dpi) were significantly enriched. Contrastingly, the GO term "response to abiotic stimulus" was down regulated at both time points analysed. These results may support future breeding efforts toward the development of cultivars with higher resistance level to black scurf disease or the development of new control strategies.

Necrotrophic lifestyle of Rhizoctonia solani AG3-PT during interaction with its host plant potato as revealed by transcriptome analysis.

The soil-borne pathogen Rhizoctonia solani infects a broad range of plants worldwide and is responsible for significant crop losses. Rhizoctonia solani AG3-PT attacks germinating potato sprouts underground while molecular responses during interaction are unknown. To gain insights into processes induced in the fungus especially at early stage of interaction, transcriptional activity was compared between growth of mycelium in liquid culture and the growing fungus in interaction with potato sprouts using RNA-sequencing. Genes coding for enzymes with diverse hydrolase activities were strongly differentially expressed, however with remarkably dissimilar time response. While at 3 dpi, expression of genes coding for peptidases was predominantly induced, strongest induction was found for genes encoding hydrolases acting on cell wall components at 8 dpi. Several genes with unknown function were also differentially expressed, thus assuming putative roles as effectors to support host colonization. In summary, the presented analysis characterizes the necrotrophic lifestyle of R. solani AG3-PT during early interaction with its host.

Draft genome sequence of the potato pathogen Rhizoctonia solani AG3-PT isolate Ben3.

The basidiomycetes fungus Rhizoctonia solani AG3 is responsible for black scurf disease on potato and occurs in each potato growing area world-wide. In this study, the draft genome sequence of the black scurf pathogen R. solani AG3-PT isolate Ben3 is presented. The genome sequence of R. solani AG3-PT isolate Ben3 consists of 1385 scaffolds. These scaffolds amount to a size of approx. 51 Mb. Considering coverage analyses of contigs, the size of the diploid genome was estimated to correspond to 116 Mb. Gene prediction by applying AUGUSTUS (3.2.1.) resulted in 12,567 identified genes. Based on automatic annotation using GenDBE, genes potentially encoding cellulases and enzymes involved in secondary metabolite synthesis were identified in the R. solani AG3-PT isolate Ben3 genome. Comparative analyses including the R. solani AG3 isolate Rhs1AP, also originating from potato, revealed first insights into core genes shared by both isolates and unique determinants of each isolate.

Interaction of moderate UV-B exposure and temperature on the formation of structurally different flavonol glycosides and hydroxycinnamic acid derivatives in kale (Brassica oleracea var. sabellica).

Kale has a high number of structurally different flavonol glycosides and hydroxycinnamic acid derivatives. In this study we investigated the interaction of moderate UV-B radiation and temperature on these compounds. Kale plants were grown at daily mean temperatures of 5 or 15 °C and were exposed to five subsequent daily doses (each 0.25 kJ m(-2) d(-1)) of moderate UV-B radiation at 1 d intervals. Of 20 phenolic compounds, 11 were influenced by an interaction of UV-B radiation and temperature, e.g., monoacylated quercetin glycosides. Concomitantly, enhanced mRNA expression of flavonol 3'- hydroxylase showed an interaction of UV-B and temperature, highest at 0.75 kJ m(-2) and 15 °C. Kaempferol glycosides responded diversely and dependent on, e.g., the hydroxycinnamic acid residue. Compounds containing a catechol structure seem to be favored in the response to UV-B. Taken together, subsequent exposure to moderate UV-B radiation is a successful tool for enhancing the flavonoid profile of plants, and temperature should be considered.

Functional analysis of the pyrimidine de novo synthesis pathway in solanaceous species.

Pyrimidines are particularly important in dividing tissues as building blocks for nucleic acids, but they are equally important for many biochemical processes, including sucrose and cell wall polysaccharide metabolism. In recent years, the molecular organization of nucleotide biosynthesis in plants has been analyzed. Here, we present a functional analysis of the pyrimidine de novo synthesis pathway. Each step in the pathway was investigated using transgenic plants with reduced expression of the corresponding gene to identify controlling steps and gain insights into the phenotypic and metabolic consequences. Inhibition of expression of 80% based on steady-state mRNA level did not lead to visible phenotypes. Stepwise reduction of protein abundance of Asp transcarbamoylase or dihydro orotase resulted in a corresponding inhibition of growth. This was not accompanied by pleiotropic effects or by changes in the developmental program. A more detailed metabolite analysis revealed slightly different responses in roots and shoots of plants with decreased abundance of proteins involved in pyrimidine de novo synthesis. Whereas in leaves the nucleotide and amino acid levels were changed only in the very strong inhibited plants, the roots show a transient increase of these metabolites in intermediate plants followed by a decrease in the strong inhibited plants. Growth analysis revealed that elongation rates and number of organs per plant were reduced, without large changes in the average cell size. It is concluded that reduced pyrimidine de novo synthesis is compensated for by reduction in growth rates, and the remaining nucleotide pools are sufficient for running basic metabolic processes.

Molecular analysis of de novo pyrimidine synthesis in solanaceous species.

The de novo synthesis of pyrimidine nucleotides in plants has been analysed on a molecular level with special focus on cDNA cloning and structure analysis of all genes involved and their expression pattern during development. The exhaustive cloning of all cDNAs resulted from screening with heterologous cDNAs or by using complementation strategies with Escherichia coli mutants and subsequent enzyme activity measurements. Southern hybridization and comparison with the Arabidopsis genome reveals plant specific aspects and a simple genomic organization of pyrimidine synthesis in plants, which is superimposed by the postulated, complex subcellular compartmentalization. Northern hybridization evinces coordinated expression of all genes under developmental control during tobacco leaf growth.