Reactive Oxygen Species Play a Role in the Infection of the Necrotrophic Fungi, Rhizoctonia solani in Wheat

Rhizoctonia solani is a nectrotrophic fungal pathogen that causes billions of dollars of damage to agriculture worldwide and infects a broad host range including wheat, rice, potato and legumes. In this study we identify wheat genes that are differentially expressed in response to the R. solani isolate, AG8, using microarray technology. A significant number of wheat genes identified in this screen were involved in reactive oxygen species (ROS) production and redox regulation. Levels of ROS species were increased in wheat root tissue following R. solani infection as determined by Nitro Blue Tetrazolium (NBT), 3,3'-diaminobenzidine (DAB) and titanium sulphate measurements. Pathogen/ROS related genes from R. solani were also tested for expression patterns upon wheat infection. TmpL, a R. solani gene homologous to a gene associated with ROS regulation in Alternaria brassicicola, and OAH, a R. solani gene homologous to oxaloacetate acetylhydrolase which has been shown to produce oxalic acid in Sclerotinia sclerotiorum, were highly induced in R. solani when infecting wheat. We speculate that the interplay between the wheat and R. solani ROS generating proteins may be important for determining the outcome of the wheat/R. solani interaction

Dianionic amidinates at silicon and germanium centers: Four-, six- and eight-membered rings

Segmueller T, Schlueter PA, Drees M, et al. Dianionic amidinates at silicon and germanium centers: Four-, six- and eight-membered rings. In: Journal of Organometallic Chemistry. JOURNAL OF ORGANOMETALLIC CHEMISTRY. Vol 692. ELSEVIER SCIENCE SA; 2007: 2789-2799.At variance to an earlier finding, the reaction of Me2SiCl2 with Li[(Me)N-C(Ph)-NH] (1a), in the presence of a base, gives a six-membered ring molecule mu-[(Ph)(MeN)C-N][-SiMe2-N-C(Ph) N(Ph)-SiMe2-] (s3a), whereas with Li[(PrN)-Pr-i-C(Ph)-NH] (1b), a four-mernbered ring molecule mu-[(PrN)-Pr-i(Ph)C-N](2)(SiMe2)(2) (s4b) was formed. In contrast, with Li[(BuN)-Bu-t-C(Ph)-NH] (1c), no such reaction occurred. Obviously, a delicate influence of steric effects has to be taken into account. In fact, the latter amidinate reacts with GeCl2 to form an eight-membered ring molecule [(BuN)-Bu-t-C(Ph)-N-Ge](4) (5c) without adding an additional base. The compounds are fully characterized and their structures determined by X-ray diffraction. DFT calculations confirm the dependence on steric influences. The relative energies of ground and transition states give a rationalization the ease of transformations of the various rings via pathways with penta- and hexacoordinate silicon centers, which in turn relates to the experimental results on penta- and hexacoordinate silicon amidinates and their fluctional behavior in solution. (c) 2007 Elsevier B.V. All rights reserved