BACKGROUND: Genetic resistance to barley leaf rust caused by Puccinia hordei involves both R genes and quantitative trait loci. The R genes provide higher but less durable resistance than the quantitative trait loci. Consequently, exploring quantitative or partial resistance has become a favorable alternative for controlling disease. Four quantitative trait loci for partial resistance to leaf rust have been identified in the doubled haploid Steptoe (St)/Morex (Mx) mapping population. Further inv ...[more]
Project description:The aim of this study was to conduct a genome-wide analysis for constituent tuber carotenoid QTL. Using a genetical genomics approach samples from clones with similar carotenoid traits were bulked and patterns of gene expression were measured for each bulk by microarray analysis. Variation of gene expression within these bulks may be due to either polymorphisms located near to or within the gene (cis-eQTL) or indirectly from a distant location on the genome (trans-eQTL). Differentially expressed clones from bulks with contrasting carotenoid traits were genetically mapped in order to re-enforce the QTL analysis, and provide a rapid means of developing gene markers closely associated with the target traits.
Project description:The bacterial pathogen Erwinia amylovora is the causal agent of fire blight, an economically significant disease of apple and pear. Disease initiation by E. amylovora requires the translocation of effector proteins into host cells by the hypersensitive response and pathogenicity (hrp) type III secretion system (T3SS). The alternate sigma factor HrpL positively regulates the transcription of structural and translocated components of the T3SS via hrp promoter elements. To characterize genome-wide hrpL-dependent gene expression in E. amylovora Ea1189, wild-type and Ea1189hrpL strains were cultured in hrp-inducing minimal medium, and total RNA was compared using a custom microarray designed to represent the annotated genes of E. amylovora ATCC 49946. Results revealed 24 genes differentially-regulated in Ea1189hrpL compared to Ea1189 with fold-change expression ratios greater than 1.5; of these, the expression of 19 genes was up-regulated while five genes exhibited negative regulation. To expand our understanding of the HrpL regulon and to elucidate direct versus indirect hrpL-mediated effects on gene expression, the genome of E. amylovora ATCC 49946 was examined in silico using a hidden Markov model assembled from known Erwinia spp. hrp promoters. This technique identified 21 putative type III novel hrp promoters; of these, 8+ were validated with quantitative polymerase chain reaction based on expression analyses. In total, hrpL-regulated genes encode all known components of the hrp T3SS and 5 putative type III effectors. Eight genes displayed apparent indirect hrpL regulation suggesting that the hrpL regulon is connected to downstream signaling networks. Construction of deletion mutants of three novel hrpL-regulated genes has resulted in the identification of additional virulence factors in E. amylovora as well as mutants displaying abnormal motility and biofilm phenotypes.
Project description:Plant cell wall degrading enzymes (PCWDEs) are key virulence determinants in the pathogenesis of the potato pathogen, Pectobacterium atrosepticum. In this study, we report the impact on virulence of a transposon insertion mutation in the metJ gene that codes for the repressor of the methionine biosynthesis regulon. In a mutant strain defective for the small regulatory RNA rsmB, PCWDEs are not produced and virulence in potato tubers is almost totally abolished. However, when the metJ gene is disrupted in this background, the rsmB- phenotype is suppressed and virulence and PCWDE production are restored. Additionally, when metJ is disrupted, production of the quorum sensing signal, N-(3-oxohexanoyl)-homoserine lactone, is induced precociously. The metJ mutant strains showed pleiotropic transcriptional impacts affecting approximately a quarter of the genome. Genes involved in methionine biosynthesis were most highly up-regulated, but many virulence-associated transcripts were also upregulated. This is the first report of the impact of the MetJ repressor on virulence in bacteria.
Project description:The goal of the experiments was to profile and analyze gene activity during murine pre-implantation development. Samples were collected at twelve time points from the germinal vesicle (GV) stage oocyte to the late (expanded) blastocyst.