The rice Xa21 gene, which confers resistance to Xanthomonas oryzae pv. oryzae race 6, was isolated by positional cloning. Fifty transgenic rice plants carrying the cloned Xa21 gene display high levels of resistance to the pathogen. The sequence of the predicted protein, which carries both a leucine-rich repeat motif and a serine-threonine kinase-like domain, suggests a role in cell surface recognition of a pathogen ligand and subsequent activation of an intracellular defense response. Characterization of Xa21 should facilitate understanding of plant disease resistance and lead to engineered resistance in rice.

The rice Xa21 gene confers resistance to Xanthomonas oryzae pv oryzae in a race-specific manner. Analysis of the inheritance patterns and resistance spectra of transgenic plants carrying six Xa21 gene family members indicated that one member, designated Xa21D , displayed a resistance spectrum identical to that observed for Xa21 but conferred only partial resistance. Xa21D encodes a receptor-like protein carrying leucine-rich repeat (LRR) motifs in the presumed extracellular domain. The Xa21D transcript terminates shortly after the stop codon introduced by the retrotransposon Retrofit . Comparison of nucleotide substitutions in the LRR coding regions of Xa21 and Xa21D provided evidence of adaptive selection. Both functional and evolutionary evidence indicates that the Xa21D LRR domain controls race-specific pathogen recognition. INTRODUCTIONReceptor kinases (RKs) play a key role in important cellular processes in plants and animals (Fantl et al., 1993; Song et al., 1995;Becraft et al., 1996;Heldin and Ostman, 1996; Stein et al., 1996;Ten Dijke et al., 1996;Torii et al., 1996;Li and Chory, 1997). Three functional domains are commonly associated with RK proteins: an extracellular domain, a transmembrane domain, and an intracellular catalytic domain. Studies of animal RKs have revealed a common mechanism for RK-mediated cellular signaling (Hunter, 1995;Pawson, 1995;Heldin and Ostman, 1996). In this model, ligand binding to the extracellular receptor domain induces receptor dimerization and subsequent activation of the intracellular kinase domain. The specificity of the interaction with the ligand is controlled by amino acid residues in the extracellular domain (Heldin and Ostman, 1996).Plant RKs can be divided into six subclasses based on the protein motif in the presumed extracellular domains (Walker, 1994;Becraft et al., 1996). The largest subclass of plant RKs is the leucine-rich repeat (LRR) group, which encodes proteins with an extracellular domain containing 20 to 25 imperfect repeats of a 24-amino acid leucine-rich motif. The LRR subclass of plant RKs includes proteins that govern pollen development, plant elongation, regulation of meristem and flower development, disease resistance, and brassinosteroid signal transduction, as well as other functions that remain to be determined (Chang et al., 1992;Valon et al., 1993; Song et al., 1995;Torii et al., 1996;Clark et al., 1997;Li and Chory, 1997). Plant LRRs have also been found in secreted proteins (polygalacturonase inhibitor proteins or PGIPs) (De Lorenzo et al., 1994) and in membrane-bound resistance gene products (Dixon et al., 1996). LRR domains are present in a variety of proteins involved in peptide ligand recognition, cell adhesion, and various other functions and are thought to mediate protein-protein interactions (Braun et al., 1991;Kobe and Deisenhofer, 1994).The cloning and characterization of the rice Xa21 gene demonstrated that LRR-containing RKs function in plant disease resistance. Xa21 confers race-specific resistance to Xanthomonas oryzae pv ...

Copy number variations (CNVs) are important source of genetic variation, which can affect diverse economic traits through a variety of mechanisms. In addition, genome scan can identify many quantitative trait loci (QTLs) for the economic traits, while genome-wide association studies (GWAS) can localize genetic variants associated with the phenotypic variations. Here, we developed a method called GWAScore which collected GWAS summary data to identify potential candidates, and integrated CNVs into QTLs and high confidence GWAScore regions to detect crucial CNV markers for sheep growth traits. We got 197 candidate genes which were overlapping with the candidate CNVs. Some crucial genes (MYLK3, TTC29, HERC6, ABCG2, RUNX1, etc.) showed significantly elevated GWAScore peaks than other candidate genes. In this study, we developed the GWAScore method to excavate the potential value of candidate genes as markers for the sheep molecular breeding.

Recurrent miscarriage (RM) is a complex clinical problem. However, specific diagnostic biomarkers and candidate regulatory targets have not yet been identified. To explore RM-related biological markers and processes, we performed a genome-wide DNA methylation analysis using the Illumina Infinium HumanMethylation450 array platform. Methylation variable positions and differentially methylated regions (DMRs) were selected using the Limma package in R language. Thereafter, gene ontology (GO) enrichment analysis and pathway enrichment analysis were performed on these DMRs. A total of 1,799 DMRs were filtered out between patients with RM and healthy pregnant women. The GO terms were mainly related to system development, plasma membrane part, and sequence-specific DNA binding, while the enriched pathways included cell adhesion molecules, type I diabetes mellitus, and ECM–receptor interactions. In addition, genes, including ABR, ALCAM, HLA-E, HLA-G, and ISG15, were obtained. These genes may be potential candidates for diagnostic biomarkers and possible regulatory targets in RM. We then detected the mRNA expression levels of the candidate genes. The mRNA expression levels of the candidate genes in the RM group were significantly higher than those in the control group. However, additional research is still required to confirm their potential roles in the occurrence of RM.