High-density genetic linkage maps are necessary for precisely mapping quantitative trait loci (QTLs) controlling grain shape and size in wheat. By applying the Infinium iSelect 9K SNP assay, we have constructed a high-density genetic linkage map with 269 F 8 recombinant inbred lines (RILs) developed between a Chinese cornerstone wheat breeding parental line Yanda1817 and a high-yielding line Beinong6. The map contains 2431 SNPs and 128 SSR & EST-SSR markers in a total coverage of 3213.2 cM with an average interval of 1.26 cM per marker. Eighty-eight QTLs for thousand-grain weight (TGW), grain length (GL), grain width (GW) and grain thickness (GT) were detected in nine ecological environments (Beijing, Shijiazhuang and Kaifeng) during five years between 2010–2014 by inclusive composite interval mapping (ICIM) (LOD≥2.5). Among which, 17 QTLs for TGW were mapped on chromosomes 1A, 1B, 2A, 2B, 3A, 3B, 3D, 4A, 4D, 5A, 5B and 6B with phenotypic variations ranging from 2.62% to 12.08%. Four stable QTLs for TGW could be detected in five and seven environments, respectively. Thirty-two QTLs for GL were mapped on chromosomes 1B, 1D, 2A, 2B, 2D, 3B, 3D, 4A, 4B, 4D, 5A, 5B, 6B, 7A and 7B, with phenotypic variations ranging from 2.62% to 44.39%. QGl.cau-2A.2 can be detected in all the environments with the largest phenotypic variations, indicating that it is a major and stable QTL. For GW, 12 QTLs were identified with phenotypic variations range from 3.69% to 12.30%. We found 27 QTLs for GT with phenotypic variations ranged from 2.55% to 36.42%. In particular, QTL QGt.cau-5A.1 with phenotypic variations of 6.82–23.59% was detected in all the nine environments. Moreover, pleiotropic effects were detected for several QTL loci responsible for grain shape and size that could serve as target regions for fine mapping and marker assisted selection in wheat breeding programs.

This genome-wide search for susceptibility genes to type 2 diabetes/impaired glucose homeostasis (IGH) was performed on a relatively homogenous Chinese sample with a total number of 257 pedigrees and 385 affected sibpairs. Two regions showed significant linkage to type 2 diabetes/IGH in the Chinese. T ype 2 diabetes is a complex disease that develops in individuals with genetic susceptibility to impaired insulin secretion, as well as to impaired insulin sensitivity, in the presence of appropriate environmental factors, particularly those leading to obesity (1). Marked increases in the prevalence of type 2 diabetes occur in those societies or countries that have experienced tremendous economic development from a starting point of an impoverished economic base (2). Along with the economic development in China, nationwide surveys have revealed an increase in the prevalence of diabetes in the adult population from 0.9 to 2.4% over the years 1980 -1994 (3). In Shanghai, China, the prevalence of diabetes was only 1.0% in 1978 but had reached 9.8% by the turn of the last century, i.e., there has been a 10-fold increase within the last two decades in the Shanghai population alone (4,5).Genetic heterogeneity of type 2 diabetes has been suggested among ethnic groups (6). This may be one of the reasons for the different locations of susceptibility loci reported to be linked to type 2 diabetes among ethnic groups in genome-wide scans (7-22). In the large geographic area of China, 56 ethnic groups are officially recognized, the Han being the largest. The Chinese of Han ethnicity reside throughout China, mostly in the eastern and central regions. Studies of the origin of the East Asian population revealed that, even within the Han ethnic group, considerable genetic heterogeneity might exist according to geographical location (23)(24)(25). Because appropriate definition of a more homogenous sample set is one of the issues for a genome-wide screen for type 2 diabetes susceptibility genes, geographical genetic heterogeneity should be considered when conducting such a study on the Chinese population. Thus, the genome-wide screen reported in this study was performed with Chinese pedigrees recruited from a limited geographic area in China. RESEARCH DESIGN AND METHODSPedigrees for this study were selected from a sampling scheme for the collection of multiplex diabetic families aimed at the genetic studies of type 2 Additional information for this article can be found in an online appendix at http://diabetes.diabetesjournals.org. ASP, affected sibpair; IA-2, protein tyrosine phosphatase-like protein; IGH, impaired glucose homeostasis; LOD, logarithm of odds; MLS, maximum likelihood score; MODY, maturity-onset diabetes of the young; NPL, nonparametric linkage.

Pulmonary adenoma susceptibility 1 (Pas1), located on chromosome 6, is the major locus affecting inherited predisposition to lung tumor development in mice. We have fine mapped the Pas1 locus to a region of Ϸ0.5 megabases by using congenic strains of mice, constructed by placing the Pas1 region of chromosome 6 from A͞J mice onto the genetic background of C57BL͞6J mice. Systematic characterization of Pas1 candidates establishes the Las1 (lung adenoma susceptibility 1) and Kras2 (Kirsten rat sarcoma oncogene 2) genes as primary candidates for the Pas1 locus. Clearly, Kras2 affects lung tumor progression only, and Las1 is likely to affect lung tumor multiplicity. L ung cancer is the leading cause of cancer death in men and women in the United States (1). Although lung cancer is largely induced by smoking, there is strong evidence for genetic susceptibility and gene-environment interactions in its development (2-5). However, genetic heterogeneity and enormous variation in exposure levels to environmental agents make it difficult to identify lung cancer susceptibility loci in humans. Thus, inbred mouse models offer an effective means of identifying candidate lung cancer susceptibility loci (6)(7)(8)(9)(10)(11)(12)(13)(14). Inbred strains of mice have different susceptibilities to spontaneous and carcinogen-induced lung tumor formation (6, 7). The A͞J strain is the most susceptible to lung tumorigenesis, whereas the C3H and C57BL͞6J strains are among the most resistant (6, 7). Linkage study using (A͞J ϫ C3H͞HeJ)F 2 and (A͞J ϫ C57BL͞6J)F 2 mice has demonstrated that pulmonary adenoma susceptibility 1 (Pas1) is the major lung tumor susceptibility locus in mice, which has been mapped to the distal region of chromosome 6 and accounts for Ϸ50% of the phenotypic variance (9, 10). Here we provide definitive evidence to support the candidacy of both Las1 (lung adenoma susceptibility 1) and Kras2 (Kirsten rat sarcoma oncogene 2) as the Pas1 genes on mouse chromosome 6. We are not aware of the identification of any other candidates for this quantitative trait locus (QTL) in either mouse models or humans since the initial mapping of the Pas1 QTL in 1993 (9). Materials and MethodsConstruction of Congenic Strains. Inbred A͞J and C57BL͞6J mice were purchased from The Jackson Laboratory. The basic breeding scheme in the study was to put an Ϸ26.1-centimorgan fragment of chromosome 6, encompassed by D6MIT54 and D6MIT373 markers from the lung tumor-susceptible A͞J strain, onto the genetic background of lung tumor-resistant C57BL͞6J mice. A͞J mice were crossed initially to C57BL͞6J mice. F 1 progeny were backcrossed to C57BL͞6J mice to produce the first backcross generation (N 2 ). The N 2 generation heterozygous for the chromosome region of interest was then backcrossed again to C57BL͞6J mice to produce the N 3 generation. This process was repeated for a total of seven backcrosses. At the N 5 generation, additional microsatellite markers on chromosomes 9, 10, 17, and 19 (D9MIT75, D9MIT355, D9MIT35, D10MIT106, D10MIT2, D10MIT126, D17MIT...

Summary Cleistogenes songorica (2n = 4x = 40) is a desert grass with a unique dimorphic flowering mechanism and an ability to survive extreme drought. Little is known about the genetics underlying drought tolerance and its reproductive adaptability. Here, we sequenced and assembled a high‐quality chromosome‐level C. songorica genome (contig N50 = 21.28 Mb). Complete assemblies of all telomeres, and of ten chromosomes were derived. C. songorica underwent a recent tetraploidization (~19 million years ago) and four major chromosomal rearrangements. Expanded genes were significantly enriched in fatty acid elongation, phenylpropanoid biosynthesis, starch and sucrose metabolism, and circadian rhythm pathways. By comparative transcriptomic analysis we found that conserved drought tolerance related genes were expanded. Transcription of CsMYB genes was associated with differential development of chasmogamous and cleistogamous flowers, as well as drought tolerance. Furthermore, we found that regulation modules encompassing miRNA, transcription factors and target genes are involved in dimorphic flower development, validated by overexpression of CsAP2_9 and its targeted miR172 in rice. Our findings enable further understanding of the mechanisms of drought tolerance and flowering in C. songorica, and provide new insights into the adaptability of native grass species in evolution, along with potential resources for trait improvement in agronomically important species.

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