Knowledge of the complete genomic DNA sequence of an organism allows a systematic approach to defining its genetic components. The genomic sequence provides access to the complete structures of all genes, including those without known function, their control elements, and, by inference, the proteins they encode, as well as all other biologically important sequences. Furthermore, the sequence is a rich and permanent source of information for the design of further biological studies of the organism and for the study of evolution through cross-species sequence comparison. The power of this approach has been amply demonstrated by the determination of the sequences of a number of microbial and model organisms. The next step is to obtain the complete sequence of the entire human genome. Here we report the sequence of the euchromatic part of human chromosome 22. The sequence obtained consists of 12 contiguous segments spanning 33.4 megabases, contains at least 545 genes and 134 pseudogenes, and provides the first view of the complex chromosomal landscapes that will be found in the rest of the genome.

We have sequenced a 1.1-Mb region of human chromosome 22q containing the dosage-sensitive gene(s) responsible for cat eye syndrome (CES) as well as the 450-kb homologous region on mouse chromosome 6. Fourteen putative genes were identified within or adjacent to the human CES critical region (CESCR), including three known genes (IL-17R,ATP6E, and BID) and nine novel genes, based on EST identity. Two putative genes (CECR3 and CECR9) were identified, in the absence of EST hits, by comparing segments of human and mouse genomic sequence around two solitary amplified exons, thus showing the utility of comparative genomic sequence analysis in identifying transcripts. Of the 14 genes, 10 were confirmed to be present in the mouse genomic sequence in the same order and orientation as in human. Absent from the mouse region of conserved synteny areCECR1, a promising CES candidate gene from the center of the contig, neighboring CECR4, and CECR7 andCECR8, which are located in the gene-poor proximal 400 kb of the contig. This latter proximal region, located ∼1 Mb from the centromere, shows abundant duplicated gene fragments typical of pericentromeric DNA. The margin of this region also delineates the boundary of conserved synteny between the CESCR and mouse chromosome 6. Because the proximal CESCR appears abundant in duplicated segments and, therefore, is likely to be gene poor, we consider the putative genes identified in the distal CESCR to represent the majority of candidate genes for involvement in CES.

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Leaf rust is an important wheat disease that is a significant hindrance for wheat production in most areas of the world. Breeding resistant cultivars can effectively and economically control the disease. In the present study, a wheat collection consisting of 100 cultivars from China and 18 improved germplasms from global landrace donors together with 36 known single Lr gene lines were tested with 20 strains of Puccinia triticina Eriks. in the seedling stage to postulate the Lr gene in the cultivars and germplasms. In addition, 12 diagnostic molecular markers specific to 10 Lr genes were used to detect the presence of the Lr genes in the wheat collection. Resistance to leaf rust of these cultivars at the adult plant stage was tested in fields under natural infection during the 2016 to 2018 cropping seasons in Baoding, Hebei Province. The gene postulation combined with molecular marker detection showed that six Lr genes (Lr1, Lr26, Lr33, Lr34, Lr45, and Lr46) were identified in 44 wheat accessions, including 37 cultivars and seven improved germplasms. Among the 44 wheat accessions postulated with Lr genes, Lr1 was present in four accessions, Lr26 in 12 accessions, Lr33 in two accessions, Lr34 in 14 accessions, Lr45 in three accessions, and Lr46 in 16 accessions. In the collection of 118 cultivars/germplasms, 34 wheat lines displayed adult-plant resistance carrying Lr34, Lr46, and/or underdetermined genes. Therefore, a high level of leaf rust resistance can be achieved through the combination of all-stage resistance and adult-plant resistance genes together in wheat cultivars.

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