Resistance to <Emphasis Type="Italic">Phytophthora infestans</Emphasis>: exploring genes required for disease resistance in Solanaceae plants

The oomycete Phytophthora infestans is the causal agent of potato late blight, one of the most destructive and historically significant pathogens in agricultural production. A virus-induced gene silencing-based screening of the solanaceous model plant N. benthamiana resulted in revealing a wide range of resistance mechanisms of solanaceous plants against this pathogen. In this article, we present an overview of the various pathways involved in the N. benthamiana–P. infestans pathosystem, including some of the follow-up work that was triggered by these findings. The purpose of this review is to assemble these findings and integrate them into our current understanding of plant pathogen defense mechanisms and discuss their potential application for the development of potato resistance to P. infestans.     

Novel capsid genes (g23) of T4-type bacteriophages in a Japanese paddy field

Viruses exist everywhere on the planet. Recent development in viral genomics confirmed that genomic information is preserved among viral subsets and can be used for phylogenetic classification of viruses and for evaluation of viral diversity in the environment. The capsid gene of T4-type bacteriophages, g23, is the most widely applied gene for evaluating the diversity of the T4-type bacteriophage family. In this study, we applied denaturing gradient gel electrophoresis to PCR products of DNA with g23-specific primers that were extracted from a Japanese paddy field under long-term fertilizer trial and obtained 39 different g23 clones at the DNA level. They showed identities of 27–99% with the clones within the NCBI database at the amino acid level. They were quite distinctive from those obtained in marine environments and most of them formed six phylogenetically novel groups in the T4-type bacteriophage family with the clones obtained from another paddy field. The existence of six novel groups was confirmed from molecular analysis of all the amino acid sequences between the primers, of the amino acid sequences excluding hypervariable region, and of those of conserved regions. These findings indicate that T4-type bacteriophage communities in paddy fields consist of previously uncharacterized members phylogenetically distant from those in marine environments. The type of fertilizers and the stage during rice cultivation were not the major factors in determining T4-type bacteriophage communities in the paddy field.     

Effect of glyphosate on tryptamine production and Sekiguchi lesion formation in rice infected with Magnaporthe grisea

When exposed to light, the Sekiguchi lesion (sl) rice mutant has an enhanced resistance to Magnaporthe grisea infection responsible for Sekiguchi lesion formation and tryptamine accumulation. Glyphosate [N-(phosphonomethyl) glycine] pretreatment suppressed Sekiguchi lesion formation and tryptamine accumulation in the sl mutant after M. grisea infection even under light. This inhibition by glyphosate was blocked by the supply of exogenous tryptophan, but not by exogenous phenylalanine. In glyphosate-pretreated leaves, 5-enol-pyruvyl-shikimate-3-phosphate synthase gene expression and tryptophan biosynthesis were significantly suppressed. During tryptophan starvation, catalase activity was maintained at a high level even under light, leading to the suppression of H₂O₂ generation and DNA fragmentation. These results show a strong relationship between the tryptophan and tryptamine pathways in the induction of light-enhanced resistance to M. grisea infection in the sl mutant.     

Rinsing of Saline Water from Road Salt in a Sandy Soil by Infiltrating Rainfall: Experiments,Simulations, and Implications

Saline melt water from road salt applications that has percolated into a fine sandy soil in winter is rinsed out of the soil by infiltrating rainwater in the following warmer seasons. This sequence of saturated and unsaturated flow processes associated with saline water transport in a fine sandy soil was studied by simulation and exploratory laboratory experiments. Experiments in soil columns of 300-μm sand revealed that two rinses of pure water, each of one pore volume, were sufficient to reduce the salt concentration by 99% of its original value in the soil column. Simulated time variations of salt concentration in the effluent from the column agreed with experimental results. Based on simulated and experimental results, a sandy soil must become saturated to experience pore water flow in order to efficiently rinse saline snowmelt water. Depending on the saturated hydraulic conductivity and the soil depth, days, weeks, or months of freshwater infiltration in summer are needed to rinse saline melt water from an unsaturated sandy soil after road salt applications in winter. This explains findings of significant salt concentrations in surface and shallow groundwater during summer months, long after road salt application and infiltration has ceased.     

Diversity and community structure of wood-inhabiting fungi found in Japanese wooden houses analyzed by the next-generation sequencing

The diversity and community structures of wood-inhabiting fungi in 16 decayed wood samples from ten wooden houses in Japan were analyzed using a next-generation sequencing (NGS) to determine the fungi responsible for wood decay. DNA of fungi in decayed wood was extracted directly, the internal transcribed spacer (ITS) region in ribosomal DNA (rDNA) was amplified by polymerase chain reaction (PCR), and then, sequences of tagged ITS fragments were analyzed by NGS. Results of sequencing indicated that 68 species of ascomycetes, 37 species of basidiomycetes, and one fungus each from Mortierellales and Mucoromycetes were detected. The fungal community structures showed diversity and included various species of ascomycetes. A microscopic examination of cell wall structure in decayed wood samples suggested that some ascomycetes were soft-rot fungi. Heat map analysis indicated that the similarity in the structures of fungal communities was influenced to a greater extent by the wood species of samples than where they were used as a component.     

Effect of ensiling process of total mixed ration on fermentation profile,nutrient loss and in situ ruminal degradation characteristics of diet

This experiment aimed to determine the changes in chemical composition, fermentation profile, in situ disappearance characteristics, and nutrient losses of ensiled total mixed ration (TMR) containing steam‐flaked corn or brown rice (BR) during storage. TMRs for dairy cows, containing either steam‐flaked corn or BR at 31.9% with 15.2% rye silage, 40.5% alfalfa silage, 5.0% beet pulp and 7.0% soybean meal, were prepared (dry matter (DM) basis). Each TMR was placed in a plastic drum silo, stored at 23°C in an air‐conditioned room and sampled 0, 7, 14, 30, 90 and 210 days after preparation. In both grain sources, the fermentation products increased, while DM and starch storage losses increased and starch content greatly decreased during storage. The rapidly degradable fraction and effective ruminal degradability of DM, crude protein and starch increased during storage. These changes of dietary characteristics were large during 30 days of storage, but small after 90 days of storage. Replacing corn with BR led to increased fermentation products, starch loss and effective ruminal degradability of the ensiled TMR. These results indicate that the ensiling process of TMR changes the dietary characteristics and replacing corn with BR in TMR had a large impact on these dietary characteristics.     

吉林省白杨锈菌鉴定

 银白杨,杨属植物,广泛种植于中国东北部地区,其锈病发生特别严重。在本研究中,根据形态特征和生活史将白杨锈菌鉴定为Melampsora laricis。使用杨树锈病叶片上的担孢子对日本落叶松及白山落叶松进行接种试验,结果证实了其精子器和锈子器世代发生在落叶松植物上。     

Identification of novel haze-active beer proteins by proteome analysis

Colloidal haze reduces beer quality considerably. Four haze samples were analyzed by two-dimensional gel electrophoresis (2DE) in order to identify haze-active proteins. Several protein spots were observed in all of the four haze samples. Using mass spectrometry analysis followed by a database search identified these spots as barley dimeric alpha-amylase inhibitor (BDAI-1), CMb component of tetrameric alpha-amylase inhibitor (CMb) and trypsin inhibitor CMe precursor (CMe). These proteins were considered to be haze-active. Since haze-active proteins are adsorbed by silica gel in the beer filtration process, we eluted proteins adsorbed onto silica gel (PAS) and identified their species. These major PAS were identified as protein Z4, protein Z7 and trypsin/amylase inhibitor pUP13 (TAI), rather than BDAI-1, CMb and CMe. Furthermore, we analyzed proline compositions in the beer proteins, PAS and the haze proteins. Consequently, we found that the proline compositions of PAS were higher (ca. 20 mol%) than those in the beer proteins (ca. 10 mol%), although those of the haze-active proteins such as BDAI-1, CMb and CMe were 6.6–8.7 mol%. Our results suggest that BDAI-1, CMb and CMe are not predominant haze-active proteins, but growth factors of beer colloidal haze.     

Characteristics of bamboo tissue in relation to cooling set

To clarify the effects of tissue and structure of bamboo on its bending properties and set by cooling (bent at 90°C and cooled to 20°C with bending), the effects of set in bast-fiber-rich (B_fib) and parenchyma-cell-rich (B_par) specimens were investigated with regard to their dynamic viscoelastic properties, chemical composition, and recovery from deformation with time. The results are summarized as follows: (1) while no clear effect of the proportion of parenchyma cells and bast fibers on residual set immediately after cooling was found, the relative recovery from the deformation with time for B_fib was larger than that for B_par. (2) Slightly higher lignin content and a-cellulose were seen in B_fib than in B_par. (3) The peak temperature of loss modulus (E″) found for B_par, which was attributable to micro-Brownian motion of lignin, was obviously lower than that for B_fib. This was considered to be due to differences in the degree of condensation of lignin or higher-order structure. From these results, it was deduced that the bastfiber-rich specimen, which showed a higher peak temperature regarding thermal softening of lignin allowing the induction of insufficient thermal-softening in the range of 20° to 90°C, caused a larger recovery from deformation with time. Part of this report was presented at the 56th Annual Meeting of the Japan Wood Research Society in Akita, August 2006