Gac two-component system in Pseudomonas syringae pv. tabaci is required for virulence but not for hypersensitive reaction

Pseudomonas syringae pv. tabaci 6605 causes wildfire disease on host tobacco plants. To investigate the regulatory mechanism of the expression of virulence, Gac two-Component system-defective mutants, Delta gacA and Delta gacS, and a double mutant, Delta gacA Delta gacS, were generated. These mutants produced smaller amounts of N-acyl homoserine lactones required for quorum sensing, had lost swarming motility, and had reduced expression of virulence-related hrp genes and the algT gene required for exopolysaccharide production. The ability of the mutants to cause disease symptoms in their host tobacco plant was remarkably reduced, while they retained the ability to induce hypersensitive reaction (HR) in the nonhost plants. These results indicated that the Gac two-component system of P. syringae pv. tabaci 6605 is indispensable for virulence on the host plant, but not for HR induction in the nonhost plants.</p

Modulation of defense signal transduction by flagellin-induced WRKY41 transcription factor in Arabidopsis thaliana

Flagellin, a component of the flagellar filament of Pseudomonas syringae pv. tabaci 6605 (Pta), induces hypersensitive reaction in its non-host Arabidopsis thaliana. We identified the WRKY41 gene, which belongs to a multigene family encoding WRKY plant-specific transcription factors, as one of the flagellin-inducible genes in A. thaliana. Expression of WRKY41 is induced by inoculation with the incompatible pathogen P. syringae pv. tomato DC3000 (Pto) possessing AvrRpt2 and the non-host pathogens Pta within 6-h after inoculation, but not by inoculation with the compatible Pto. Expression of WRKY41 was also induced by inoculation of A. thaliana with an hrp-type three secretion system (T3SS)-defective mutant of Pto, indicating that effectors produced by T3SS in the Pto wild-type suppress the activation of WRKY41. Arabidopsis overexpressing WRKY41 showed enhanced resistance to the Pto wild-type but increased susceptibility to Erwinia carotovora EC1. WRKY41-overexpressing Arabidopsis constitutively expresses the PR5 gene, but suppresses the methyl jasmonate-induced PDF1.2 gene expression. These results demonstrate that WRKY41 may be a key regulator in the cross talk of salicylic acid and jasmonic acid pathways.</p

Genome size in Anthurium evaluated in the context of karyotypes and phenotypes

Little is known about the genome of Anthurium other than chromosome observations, which frequently indicate supernumerary (“B”) chromosomes. New genome size estimates for 34 species and nine cultivars presented here provide insights into genome organization and evolution in this very large genus

Faithful chaperones

This review describes the properties of some rare eukaryotic chaperones that each assist in the folding of only one target protein. In particular, we describe (1) the tubulin cofactors, (2) p47, which assists in the folding of collagen, (3) α-hemoglobin stabilizing protein (AHSP), (4) the adenovirus L4-100 K protein, which is a chaperone of the major structural viral protein, hexon, and (5) HYPK, the huntingtin-interacting protein. These various-sized proteins (102–1,190 amino acids long) are all involved in the folding of oligomeric polypeptides but are otherwise functionally unique, as they each assist only one particular client. This raises a question regarding the biosynthetic cost of the high-level production of such chaperones. As the clients of faithful chaperones are all abundant proteins that are essential cellular or viral components, it is conceivable that this necessary metabolic expenditure withstood evolutionary pressure to minimize biosynthetic costs. Nevertheless, the complexity of the folding pathways in which these chaperones are involved results in error-prone processes. Several human disorders associated with these chaperones are discussed

Effects of geological structures on rainfall‐runoff

Clarifying rainfall-runoff responses in mountainous areas is essential for disaster prediction as well as water resource management. Although runoff is considered to be significantly affected by topography, some previous studies have reported that geological structures also have significant effects on rainfall-runoff characteristics. Particularly in headwater catchments located in sedimentary rock mountains, dips and strikes may significantly affect rainwater discharge. In this study, the effects of geological structures on rainfall-runoff characteristics were investigated based on observed discharge hydrographs from 12 catchments, which lie radially from the summit of a sedimentary rock mountain. The results obtained were as follows: (1) Even though the topographic wetness index (TWI) distributions of the 12 catchments were similar, there were significant differences in their runoff characteristics; (2) Catchments with average flow direction oriented towards the strike direction (strike-oriented catchments) are characterized by large baseflows; (3) Catchments with average flow direction oriented towards the opposite dip direction (opposite dip-oriented catchments) are steep, and this results in quick storm runoff generation; (4) Catchments with average flow direction oriented toward the dip direction (dip-oriented catchments) are gentle, and this results in delayed storm runoff generation. It was presumed that in strike-oriented catchments, large quantities of groundwater flowing along the bedding planes owing to hydraulic anisotropy, exfiltrate and sustain the large amount of the observed baseflow, that is, in strike-oriented catchments, runoff is directly controlled by geological structures. Conversely, in opposite dip-oriented and dip-oriented catchments, runoff is indirectly controlled by geological structures, that is, geological structures affect slope gradients, which result in differences in storm runoff generation. Thus, this study clearly illustrates that geological structures significantly affect rainfall-runoff responses in headwater catchments located in sedimentary rock mountains