Review Article: High-Temperature Adult-Plant Resistance, Key for Sustainable Control of Stripe Rust

High-temperature adult-plant (HTAP) resistance expresses when plants grow old and the weather becomes warm. This non-race specific and durable type of resistance has been used successfully in control of wheat stripe rust in the US since early 1960s. This article describes practical procedures for identification and characterization of HTAP resistance and reviews recent studies on discovery of genes conferring HTAP resistance. Recent studies providing insights to the molecular basis for the durability of HTAP resistance will be presented. Strategies for improving levels of HTAP resistance and improving control of stripe rust through combining HTAP resistance with effective all-stage resistance will be discussed.

Ginkgo biloba leaf extract improves the cognitive abilities of rats with D-galactose induced dementia

Standardized Ginkgo biloba leaf extract has been used in clinical trials for its beneficial effects on brain func- tions, particularly in dementia. Substantial experimental evidences indicated that Ginkgo biloba leaf extract （EGB） protected neuronal cells from a variety of insults. We investigated the effect of EGB on cognitive ability and protein kinase B （PKB） activity in hippocampal neuronal cells of dementia model rats. Rats received an intra- peritoneal injection of D-galactose to induce dementia. Forty-eight Spraque-Dawley rats were randomly divided into six groups, including the control group, D-galactose group （Gal）, low-dose EGB group （EGB-L）, mid-dose EGB group （EGB-M）, high-dose EGB group （EGB-H） and treatment group. The EGB-L, EGB-M and EGB-H groups were administered with EGB and D-galactose simultaneously. Y-maze, cresyl violet staining, TUNEL assays and immunohistochemistry staining were performed to detect learning and memory abilities, morpho- logical changes in the hippocampus, neuronal apoptosis and the expressing level of phospho-PKB, respectively. Rats in the Gal group showed decreased abilities of learning and memory, and hippocampal pyramidal cell layer was damaged, while EGB administration improved learning and memory abilities. The Gal group exhibited many stained, condensed nuclei and micronuclei, either isolated or within the cytoplasm of cells （39.5 ± 1.4）. Apoptotic cells decreased in the groups of EGB-L （35.9±0.9）, EGB-M （16.8± 1.0） and EGB-H （10.1±0.8）, and there were statistical significances compared with the Gal group. Immunoreactivity of phospho-PKB was localized diffusely throughout the cytosol of cells in all groups, while the immunoreactivity of the Gal group was weak. EGB signifi- cantly attenuated learning and memory impairment in a dose-dependent manner, while it could decrease the nmber of TUNEL-positive cells, and increase the activity of PKB. Our results demonstrated that EGB attenuated memory impairment and cell apoptosis in galactose-induced dementia model rats by activating PKB.

Pathogenesis-related protein genes involved in race-specific allstage resistance and non-race specific high-temperature adultplant resistance to Puccinia striiformis f. sp. tritici in wheat

Interactions of the stripe rust pathogen （Puccinia striiformis f. sp responses. Among various genes involved in the plant-pathogen related （PR） protein genes determine different defense responses tritici） with wheat plants activate a w^ae range OT nost nteractions, the expressions of particular pathogenesis-Different types of resistance have been recognized and utilized for developing wheat cultivars for resistance to stripe rust. All-stage resistance can be detected in seedling stage and remains at high levels throughout the plant growth stages. This type of resistance is race-specific and not durable. In contrast, plants with only high-temperature adult-plant （HTAP） resistance are susceptible in seedling stage, but become resistant when plants grow older and the weather becomes warmer. HTAP resistance controlled by a single gene is partial, but usually non-race specific and durable. The objective of this study was to analyze the expression of PR protein genes involved in different types of wheat resistance to stripe rust. The expression levels of 8 PR protein genes （PR1, PRI.2, PR2, PR3, PR4, PR5, PR9 and PRIO） were quantitatively evaluated at 0, 1, 2, 7 and 14 days after inoculation in single resistance gene lines of wheat with all-stage resistance genes YrTrl, Yr76, YrSP and YrExp2 and lines carrying HTAP resistance genes Yr52, Yr59, Yr62 and Yr7B. Races PSTv-4 and PSTv-37 for compatible and incompatible interactions were used in evaluation of PR protein gene expression in wheat lines carrying all-stage resistance genes in the seedling- stage experiment while PSTv-37 was used in the HTAP experiment. Analysis of quantitative real-time polymerase chain reaction （qRT-PCR） revealed that all of the PR protein genes were involved in the different types of resistance controlled by different Yr genes. However, these genes were upregulated at different time points and at different levels during the infection process among the wheat lines with different Yr genes for either all-stage resistance or HTAP resistance. Some of the genes were also induced in compatible interactions, but the levels were almost always higher in the incompatible interaction than in the compatible interaction at the same time point for each Yr gene. These results indicate that both salicylic acid and jasmonate signaling pathways are involved in both race-specific all-stage resistance and non-race specific HTAP resistance. Although expressing at different stages of infection and at different levels, these PR protein genes work in concert for contribution to different types of resistance controlled by different Yr genes.

Association Analysis of SP-SNPs and Avirulence Genes in Puccinia striiformis f. sp. tritici, the Wheat Stripe Rust Pathogen

Puccinia striiformis f. sp. tritici (Pst) is one of the pathogenic fungi on wheat, caused stripe rust that is a great threat for wheat production all over the world. Intensive efforts have been made to study genetics of wheat resistance to this disease, but few on avirulence of the pathogen due mainly to the nature of obligate biotrophism and the lack of systems for studying its genetics and molecular manipulations. To overcome these limitations, a natural Pst population comprising 352 isolates representative of a diverse virulence spectrum was genotyped using 97 secreted protein-single nucleotide polymorphism (SP-SNP) markers to identify candidate avirulence genes using association analysis. Among avirulence genes corresponding to 19 resistance genes, significantly associated SP-SNP markers were detected for avirulence genes AvYr1, AvYr2, AvYr6, AvYr7, AvYr8, AvYr44, AvYrExp2, AvYrSP, and AvYrTye. These results indicate that association analysis can be used to identify markers for avirulence genes. This study has laid the foundation for developing more SP-SNPs for mapping avirulence genes using segregating populations that can be generated through sexual reproduction on alternate hosts of the pathogen.

Variation in Telial Formation of <i>Puccinia striiformis</i>in the United States

Puccinia striiformis, the causal agent of stripe rust in wheat, barley, and various wild grasses, produces urediniospores and teliospores on these primary or auxiliary hosts. Telial formation, which stops producing infectious urediniospores, is affected by various host and environmental conditions. However, it is not clear if variation exists among different isolates in the United States. To determine the differences in the pathogen population, 1423 isolates collected in the United States from 2013 to 2016 were tested for telial formation in the seedling stage at a diurnal temperature profile of 4&deg;C - 20&deg;C. The percentages of telial formation varied greatly among the isolates. Of the 1423 isolates, 62.97% produced telia with the percentages of telial formation ranging from 1% to 95% under the test conditions. The formation of telia was significantly affected by the year and the month when the isolates were collected. The epidemiological regions or states, host plants (wheat, barley, and grasses), and races of the isolates did not significantly affect telial formation. However, significant effects on telial formation were observed by interactions between year and region, year and race, month and region and among year, month, and region, as well as between year and month. The results showed that telial formation is a complex trait under the genetic control of the pathogen isolates for adaptation to different environments. Further studies are needed to identify genes involved in the formation of telia and the relationship of telial formation to the survival, aggressiveness, fitness, and evolution of the pathogen.

Immunoregulatory Role of B7-H1 in Chronicity of Inflammatory Responses

Pathogenesis of most chronic human diseases, including chronic infections, autoimmune diseases and cancers, often involves a persistent, unresolved inflammatory response. The molecular mechanisms that determine the conversion of an acute inflammatory response into a chronic process had puzzled researchers for many years. Recent studies reveal that B7-H1 （CD274, PD-L1）, a newly identified co-stimulatory molecule, possesses dual functions of co-stimulation of naive T cells and inhibition of activated effector T cells. The aberrant cellular expression and deregulated function of B7-H1 have been reported during chronic viral and intracellular bacterial infection, as well as in many autoimmune diseases and cancers. Importantly, the deregulation of B7-H1＇s dual functions appears to be associated with a prolonged and incomplete immune response by luring naive T cells for activation and dampening activated effector T cells. Moreover, development of strategies targeting B7-H1 signals provides a new and promising approach to manipulate the devastating diseases associated with chronic inflammation. Thus, B7-H1 may play a critical immunoregulatory role in the chronicity of inflammatory responses. Cellular ＆ Molecular Immunology. 2006;3（3）：179-187.

Gene expression profiling of Puccinia striiformis f.sp.tritici during development reveals a highly dynamic transcriptome

Puccinia striiformis f. sp. tritici （PsO causes stripe rust, one of the most important diseases of wheat worldwide, cDNA libraries had been constructed from urediniospores, germinated urediniospores and haustoria. However, little is known about the expression patterns of the genes related to the infection process and sporulation of the pathogen. In this study, a custom oligonucleotide microarray was constructed using sequences of 442 gene transcripts selected from Pst cDNA libraries. The expression patterns of the genes were determined by hybridizing the microarray with cDNA from Pst in vitro and Pst-infected wheat leaves. The time course study identified 55 transcripts that were differentially expressed during the infection process in a compatible interaction. They were identified to have functions related to the following biological processes, including carbohydrate and lipid metabolism, energy, cell signaling, protein synthesis, cell structure and division. In an incompatible interaction, 17 transcripts of the pathogen were differentially expressed in resistant wheat leaves inoculated with an avirulent Pst race, ten of which had similar expression patterns to those in the compatible interaction. Several candidates for pathogenicity and virulence/avirulence related genes were also identified. The results of quantitative real-time PCR validated the expression patterns of some selected genes. The study demonstrates that the custom oligonucleotide microarray technology is useful to determine the expression patterns of the pathogen genes involved in different types of the host--pathogen interactions and stages of development.

Genomic analysis,trajectory tracking,and field surveys reveal sources and long-distance dispersal routes of wheat stripe rust pathogen in China

Identifying sources of phytopathogen inoculum and determining their contributions to disease outbreaks are essential for predicting disease development and establishing control strategies.Puccinia striiformis f.sp.tritici(Pst),the causal agent of wheat stripe rust,is an airborne fungal pathogen with rapid virulence variation that threatens wheat production through its long-distance migration.Because of wide variation in geographic features,climatic conditions,and wheat production systems,Pst sources and related dispersal routes in China are largely unclear.In the present study,we performed genomic analyses of 154 Pst isolates from all major wheat-growing regions in China to determine Pst population structure and diversity.Through trajectory tracking,historical migration studies,genetic introgression analyses,and field surveys,we investigated Pst sources and their contributions to wheat stripe rust epidemics.We identified Longnan,the Himalayan region,and the Guizhou Plateau,which contain the highest population genetic diversities,as the Pst sources in China.Pst from Longnan disseminates mainly to eastern Liupan Mountain,the Sichuan Basin,and eastern Qinghai;that from the Himalayan region spreads mainly to the Sichuan Basin and eastern Qinghai;and that from the Guizhou Plateau migrates mainly to the Sichuan Basin and the Central Plain.These findings improve our current understanding of wheat stripe rust epidemics in China and emphasize the need for managing stripe rust on a national scale.

Effects of fermented protein feed on the growth performance of pond-raised crab

This study aimed to elucidate the effect of a pellet feed containing fermented proteins on pond-raised Chinese mitten crabs,Eriocheir sinensis in a 7-month crab feeding experiment in Gucheng Lake,Jiangsu province,China.The results showed that fermented protein could significantly increase mean weight gain,crab size and total yield compared with control group.Moreover,the mean weight of male crabs and the number of large-sized male crabs improved over those of the control group.However,feed efficiency ratio did not differ significantly between the two groups.The amino acid content in the muscles of the female crabs of both the groups was higher than that in the muscles of the male crabs.The present study suggests that fermented compound protein may be one kind of potential protein sources for E.sinensis.