F3 Lines Research Articles

Fibronectin induces macrophage migration through a SFK-FAK/CSF-1R pathway

ABSTRACTIntegrins, following binding to proteins of the extracellular matrix (ECM) including collagen, laminin and fibronectin (FN), are able to transduce molecular signals inside the cells and to regulate several biological functions such as migration, proliferation and differentiation. Besides activation of adaptor molecules and kinases, integrins transactivate Receptor Tyrosine Kinases (RTK). In particular, adhesion to the ECM may promote RTK activation in the absence of growth factors. The Colony-Stimulating Factor-1 Receptor (CSF-1R) is a RTK that supports the survival, proliferation, and motility of monocytes/macrophages, which are essential components of innate immunity and cancer development. Macrophage interaction with FN is recognized as an important aspect of host defense and wound repair. The aim of the present study was to investigate on a possible cross-talk between FN-elicited signals and CSF-1R in macrophages. FN induced migration in BAC1.2F5 and J774 murine macrophage cell lines and in human primary macrophages. Adhesion to FN determined phosphorylation of the Focal Adhesion Kinase (FAK) and Src Family Kinases (SFK) and activation of the SFK/FAK complex, as witnessed by paxillin phosphorylation. SFK activity was necessary for FAK activation and macrophage migration. Moreover, FN-induced migration was dependent on FAK in either murine macrophage cell lines or human primary macrophages. FN also induced FAK-dependent/ligand-independent CSF-1R phosphorylation, as well as the interaction between CSF-1R and β1. CSF-1R activity was necessary for FN-induced macrophage migration. Indeed, genetic or pharmacological inhibition of CSF-1R prevented FN-induced macrophage migration. Our results identified a new SFK-FAK/CSF-1R signaling pathway that mediates FN-induced migration of macrophages.

Adult plant stripe rust resistance gene Yr71 maps close to Lr24 in chromosome 3D of common wheat

Australian cultivar Sunco carries three adult plant stripe rust resistance genes. One of these genes corresponded to Yr18 in chromosome 7DS; the second, YrCK, was mapped on chromosome 2D. Here, we describe the characterization of the third adult plant resistance (APR) gene from Sunco. Sunco/2*Avocet S-derived lines SA65 (resistant) and SA67 (susceptible) were crossed and a recombinant inbred line F6 population was generated. Monogenic segregation among SA65/SA67-derived RIL population was demonstrated and the resistance locus was designated YrSA3. Selective genotyping using an iSelect 90 K Infinium SNP array and SSR markers located YrSA3 on chromosome 3D. Development of KASP markers for SNP loci showing association with YrSA3 allowed construction of a genetic map harboring the resistance gene. Ten KASP markers (KASP_8306, KASP_9142, KASP_10438, KASP_16434, KASP_17207, KASP_20836, KASP_23518, KASP_23615, KASP_57983 and KASP_63653), one SSR marker (gwm114b) and Lr24/Sr24 were mapped 1.8 cM distal to YrSA3. Comparison of marker data indicated that the previously named seedling stripe rust resistance gene Yr45 was located proximal to YrSA3, and therefore the latter was formally designated Yr71. Two recombinants carrying Lr24/Sr24 and Yr71 in combination were identified for use as donor sources in wheat breeding programs. The robustness of gwm114b, KASP_16434, KASP_17207 and KASP_20836 for marker-assisted selection of these genes was demonstrated through tests on 74 Australian wheat cultivars.

Molecular Mapping of Stripe Rust Resistance Gene Yr76 in Winter Club Wheat Cultivar Tyee.

Tyee, one of the wheat cultivars used to differentiate races of Puccinia striiformis f. sp. tritici in the United States, was identified to have a single gene for all-stage resistance, tentatively named YrTye. To map the gene, Tyee was crossed with 'Avocet Susceptible' (AvS). Genetic analysis of the F1, F2, F2:3, and BC1 progenies confirmed a single dominant gene for resistance to race PSTv-37 that is avirulent to YrTye. A mapping population of 135 F2 plants was phenotyped with PSTv-37 and the derived F2:3 lines were tested with races PSTv-37, PSTv-40, and PSTv-79. The F2 mapping population was genotyped with simple sequence repeat (SSR) markers. A genetic map comprising 13 SSR markers located YrTye in chromosome 3AS flanked distally by SSR marker wmc11 and proximally by wmc532 at 2.6 and 3.4 cM, respectively. Amplification of Chinese Spring 3A deletion lines placed the gene in the distal bin 3AS4-0.45 to 1.00. Because YrTye is different from all formally named Yr genes in chromosomal location, we permanently name the gene Yr76. A near-isogenic line of spring common wheat was developed and selected by testing F3 lines derived from a AvS*4/Tyee cross with Tyee-avirulent and virulent races and the flanking markers. The specific SSR alleles flanking Yr76 were validated using cultivars and breeding lines with and without the gene, and showed high polymorphisms. The specificity of Yr76 is useful in differentiating P. striiformis f. sp. tritici races, and its tightly linked markers will be useful in developing resistant cultivars when combining the gene with other genes for resistance to stripe rust.

Differential expression of carotenoid biosynthetic pathway genes in two contrasting tomato genotypes for lycopene content.

Tomato (Solanum lycopersicum L.) is one of the model plant to study carotenoid biosynthesis. In the present study, the fruit carotenoid content were quantified at different developmental stages for two contrasting genotypes, viz. IIHR-249-1 and IIHR-2866 by UPLC. Lycopene content was high in IIHR-249-1 (19.45 mg/100 g fresh weight) compared to IIHR-2866 (1.88 mg/100 g fresh weight) at the ripe stage. qPCR was performed for genes that are involved in the carotenoid biosynthetic pathway to study the difference in lycopene content in fruits of both the genotypes. The expression of Phytoene synthase (PSY) increased by 36-fold and Phytoene desaturase (PDS) increased by 14-fold from immature green stage to ripe stage in IIHR-249-1. The expression of Chloroplast lycopene beta-cyclase (LCY-B) and Chromoplast lycopene beta cyclase (CYC-B) decreased gradually from the initial stage to the ripe stage in IIHR-249-1. IIHR 249-1 showed 3- and 1.8-fold decrease in gene expression for Chloroplast lycopene beta-cyclase (LCY-B) and Chromoplast lycopene beta-cyclase (CYC-B) .The F2 hybrids derived from IIHR-249-1 and IIHR-2866 were analysed at the ripe stage for lycopene content. The gene expression of Chloroplast lycopene beta-cyclase (LCY-B) and Chromoplast lycopene beta-cyclase (CYC-B) in high and low lycopene lines from F2 progenies also showed the decrease in transcript levels of both the genes in high lycopene F2 lines. We wish to suggest that the differential expression of lycopene beta-cyclases can be used in marker-assisted breeding.

Magnitude of genotype x environment interaction for bacterial leaf blight resistance in rice growing areas of Uganda

Bacterial leaf blight (BLB) of rice ( Oryzae sativa L.), caused by Xanthomonas oryzae pv. oryzae , is a major constraint in most lowland rice producing areas of Uganda. The disease is widely distributed in all irrigated and rainfed lowland rice ecosytems in the country. The pathogen (Xoo) is highly variable and its control is rather difficult. Development and deployment of host resistance is the only effective means of BLB management. The objective of this study was to determine the magnitude of genotype by environment (G x E) interaction for resistance to bacterial leaf blight in rice in Uganda. A study comprised of two sets of germplasms, a total of 30 rice genotypes comprising of 13 lines with varying levels of BLB resistance, and 17 F4 lines that had been previous generated through crossing 7 parental lines, and then advanced in bulk from F1, was conducted in Namulonge-Wakiso, Olweny-Lira and Kibimba- Bugiri districts in Uganda. The study also included 7 parental lines and 6 popular varieties used in most farmers’ fields. Variety IR 24 had been used as a universal check against BLB in Asian rice populations. Results revealed differential reactions on a set of near isogenic lines in the background of IR24, and some national and regional cultivars. IRBB1 (Xa1), IRBB2 (Xa2) and IRBB14 (Xa14) showed moderate susceptibility to susceptibility towards field pathogen populations in the three locations. Whereas genotype IRBB4 with gene Xa4 differentiated pathotypes of Kibimba and Lira from that of Namulonge, IRBB10 (Xa10) and IRBB11 (Xa11) differentiated pathotypes of Lira from the rest. Genotypes that had been pyramided with BLB genes of resistance, showed similar reactions to the three field populations. Generally, the near isogenic lines IRBB1, IRBB2, IRBB11 and IRBB14, had the highest leaf area damaged by disease attack. The highest was shown by IRBB11 with the Kibimba pathotypes for which disease attack was 43%. Low attack was observed on pyramided genotypes in all locations and two with single gene, i.e. IRBB8 and IRBB21, respectively. Interestingly, IR24 was as resistant as any of the pyramided combinations. Results also revealed different reactions of the tested genotypes in the three locations. The analysis of variance by AMMI partitioned the main effects of treatments into genotype, environment, and genotype x environment (G x E) interactions. Results also revealed that, the mean sum of squares due to treatments, genotypes, environments and genotype x environment interaction were significant, and contributed 48.2, 15.3, 19.3 and 13.3%, respectively, PCA1 accounted for 73.02% of the total G x E sum of squares. Key Words: Oryzae sativa , pyramid, Xanthomonas

Improvement of Rice Biomass Yield through QTL-Based Selection.

Biomass yield of rice (Oryza sativa L.) is an important breeding target, yet it is not easy to improve because the trait is complex and phenotyping is laborious. Using progeny derived from a cross between two high-yielding Japanese cultivars, we evaluated whether quantitative trait locus (QTL)-based selection can improve biomass yield. As a measure of biomass yield, we used plant weight (aboveground parts only), which included grain weight and stem and leaf weight. We measured these and related traits in recombinant inbred lines. Phenotypic values for these traits showed a continuous distribution with transgressive segregation, suggesting that selection can affect plant weight in the progeny. Four significant QTLs were mapped for plant weight, three for grain weight, and five for stem and leaf weight (at α = 0.05); some of them overlapped. Multiple regression analysis showed that about 43% of the phenotypic variance of plant weight was significantly explained (P < 0.0001) by six of the QTLs. From F2 plants derived from the same parental cross as the recombinant inbred lines, we divergently selected lines that carried alleles with positive or negative additive effects at these QTLs, and performed successive selfing. In the resulting F6 lines and parents, plant weight significantly differed among the genotypes (at α = 0.05). These results demonstrate that QTL-based selection is effective in improving rice biomass yield.

Inheritance of kernel hardness in spring wheat as measured by near-infrared reflectance spectroscopy

Kernel hardness is an important character directly associated with milling quality of hard wheat (Triticum aestivum L.). We studied the inheritance of kernel hardness with the near-infrared reflectance technique. Four segregating populations were developed from three crosses: Amidon/Grandin for population 1 at Prosper, ND; Grandin/Amidon for population 2 at Fargo, ND; Amidon/ND622 for populations 3 and 4 at Prosper, ND and Fargo, ND. Amidon has a relatively hard kernel, whereas Grandin and ND622 have satisfactory kernel hadrness for desirable milling characteristics. Populations were grown in augmented block field experiments in 1988 and 1989. Heritability estimates for kernel hardness obtained by regression of F4 on F3 lines in populations 1 and 2, were 0.28 and 0.21, respectively. The estimates for the same character obtained by regression of F5 on F4 lines in populations 3 and 4 were 0.45 and 0.52, respectively. The estimates of heritability were significant. Effects of locations on kernel hardness were not significantly different. Statistical analyses showed that heritability estimates for populations 4 and 2 were significantly different. Correlation coefficients on a plot basis indicated little or no association between grain protein concentration and kernel hardness.

Variations in physiological traits as screening tool for drought tolerance in barley (Hordeum vulgare L.)

The utilization of physiological traits in genetic improvement of drought tolerance in barley (Hordeum vulgare L.) requires establishment of significant association between grain yield and the physiological traits and their genetic variations. The study was aimed at to determine variability in yield-attributes, yield and physiological traits in advance F6 lines and commercial varieties of barley, and to establish the relationship among these characters in irrigated (2 irrigations at 40 and 80 days after sowing) and rainfed (no post sowing irrigation) conditions. Yield attributes, yield and physiological traits decreased significantly in rainfed than irrigated condition. Biomass was positively and significantly associated (R2 = 0.82, P < 0.001) with grain yield. Rates of photosynthesis (Pn) of flag leaf were positively related to biomass (R2 = 0.68, P < 0.001) and grain yield (R2 = 0.52, P < 0.01). Midday (1200–1400 h) leaf relative water content (RWC) showed strong association with Pn (R2 = 0.90, P < 0.001) and biomass (R2 = 0.65, P < 0.001). Since, RWC being a simple and inexpensive trait to measure, showing strong association with Pn and biomass, which determined grain yield, could be employed as a tool to screen barley genotypes for drought tolerance.

Transgressive Segregation in an Acala Glanded × Acala Glandless Hybrid Population for the Development of Glandless Cotton Germplasm

Improvement in lint yield is vital to commercial production of glandless cotton. The objective of this study was to determine if glanded ‘Acala 1517-08’ could be converted to glandless cotton without a yield penalty by crossing breeding with an obsolete glandless cotton. From 500 F2 plants, 18 glandless individuals were selected, and their F4 lines were compared with both parents. This led to a selection of 77 F6 lines for further replicated field testing. Only five F6 lines produced 90 to 96% of Acala 1517-08 lint yield (LY), while three lines had significantly lower LY than the lower parent ‘Acala GLS’. Transgressive segregation in the negative direction was also observed for boll weight (BW) and lint percent (LP) in that four and 22 F6 lines had significantly lower values than the lower parent, respectively. Four F6 lines had significantly lower fiber length (UHM) than the lower parent Acala 1517-08, while five lines had longer UHM than the higher parent Acala GLS. Ten F6 lines had weaker fibers than the lower parent Acala 1517-08, but none had stronger fibers than Acala GLS. Most F6 lines had micronaire (MIC) between the two parents except for one with higher MIC than the higher parent and five with lower MIC than the lower parent Acala GLS. In conclusion, positive transgressive segregation for LY, LP and BW should not be expected in this Acala × Acala cross, while negative transgressive segregations occurred frequently for the three traits and fiber strength. For UHM and MIC, negative transgressive segregations occurred more frequently than positive ones. Overall, there was no transgressive segregation for fiber uniformity, elongation and short fiber content.

Analysis of the genetic divergence of soybean lines through hierarchical and Tocher optimization methods.

This study aimed to evaluate the clustering pattern consistency of soybean (Glycine max) lines, using seven different clustering methods. Our aim was to evaluate the best method for the identification of promising genotypes to obtain segregating populations. We used 51 generations F5 and F6 soybean lines originating from different hybridizations and backcrosses obtained from the soybean breeding program of Universidade Federal de Uberlândia in addition to three controls (Emgopa 302, BRSGO Luziânia, and MG/BR46 Conquista). We evaluated the following agronomic traits: number of days to flowering, number of days to maturity, height of the plant at maturity, insertion height of the first pod, grain yield, and weight of 100 seeds. The data was submitted to analyses of variance followed by average Euclidean distance matrix estimation used as measure of dissimilarity. Subsequently, clusters were formed using the Tocher method and dendrograms were constructed using the hierarchical methods simple connection (nearest neighbor), complete connection (most distant neighbor), Ward, median, average within cluster connection. The nearest neighbor method presented the largest number of genotypes in group I and showed the greatest similarity with the Tocher optimization method. The joint use of these two methodologies allows for differentiation of the most genetically distant genotypes that may constitute the optimal parents in a breeding program.

A 3D culture model study monitoring differentiation of dental epithelial cells into ameloblast-like cells

The present study was designed to investigate whether a three dimensional (3D) culture of the rat incisor-derived dental epithelial cell line SF2 enhances its differentiation into ameloblast-like cells.

Development of dominant sequence characterized amplified region (SCAR) marker linked with plume moth (Exelastis atomosa Walsingham 1886) resistance in pigeon-pea

The mode of gene action governing resistance to plume moth (Exelastis atomosa Walsingham 1886) derived from pigeon-pea (Cajanus scarabaeoides (L.) Thouars) accession ICPW-94 has been determined and the resistance alleles have been designated as PPM1. The progenies of F2 population and F3 families derived from an interspecific cross C. cajan (L.) Huth ('ICP-26') x C. scarabaeoides (accession ICPW-94) revealed monogenic gene action for resistance to plume moth, and the dominant control by single locus or cluster of tightly linked alleles. Bulked segregant analysis (BSA) of 116 F2 progenies by using 143 parental polymorphic RAPD primers could identify a fragment OPA09910 associated with plume moth resistance in coupling phase of linkage. Further single plant analysis of the 116 F2 mapping population revealed OPA09910 was linked to PPMi locus conferring host resistance to plume moth with recombination fraction (rf) value of 0.125 (12.7 cM of Kosambi function). The resistance specific fragment OPA09910 was cloned, sequenced and converted into a sequence characterized amplified region (SCAR) marker, SCOPA09942, which was also closely associated (10.3 cM) with the locus PPMl with rf value 0.102. BLAST analysis with pigeon-pea genome sequence also confirmed its occurrence in CcLG02 (Scafseq.LG_V5.0fa) and contig 01597 (AFSP01.fsa1). This SCAR marker showed reasonable screening efficiency in the F2, F3, and BC1F1 lines, thus it can be used as genetic handle in marker-assisted introgression of the genomic fragment conferring plume moth resistance and screening of breeding lines in pigeon-pea.

Production of a novel Robertsonian translocation from Thinopyrum bessarabicum into bread wheat

Development of wheat-alien translocation lines will facilitate its practical utilization in wheat improvement. The objective of the present study was to produce compensating wheat--Thinopyrum bessarabicum whole arm Robertsonian translocations (RobTs) involving chromosomes 2B of wheat and 2E(b) of Th. bessarabicum through the mechanism of centric breakage-fusion. F2 population from crosses between DS2E(b)(2B) substitution line and bread wheat 'Roushan' (2n = 6x = 42, AABBDD) as female parent were made. Forty one F2 lines (L1 to L41) were screened for their chromosome composition. Three 2E(b) specific PCR-based Landmark Unique Gene (PLUG) markers were used for screening F2 progeny derived from plants double-monosomic for chromosome 2B and 2E(b). Two Rob Ts (-5%) were observed among F2 plants. Homozygous translocation (T2E(b)S.2BL) with good plant vigor and full fertility were selected from F3 families. The T2E(b)S.2BL stock has longer awn than that of its parents. It is cytogenetically stable, and may be useful in wheat improvement.

Use of genotype-environment interactions to elucidate the pattern of maize root plasticity to nitrogen deficiency.

Maize (Zea mays L.) root morphology exhibits a high degree of phenotypic plasticity to nitrogen (N) deficiency, but the underlying genetic architecture remains to be investigated. Using an advanced BC4 F3 population, we investigated the root growth plasticity under two contrasted N levels and identified the quantitative trait loci (QTLs) with QTL-environment (Q × E) interaction effects. Principal components analysis (PCA) on changes of root traits to N deficiency (ΔLN-HN) showed that root length and biomass contributed for 45.8% in the same magnitude and direction on the first PC, while root traits scattered highly on PC2 and PC3. Hierarchical cluster analysis on traits for ΔLN-HN further assigned the BC4 F3 lines into six groups, in which the special phenotypic responses to N deficiency was presented. These results revealed the complicated root plasticity of maize in response to N deficiency that can be caused by genotype-environment (G × E) interactions. Furthermore, QTL mapping using a multi-environment analysis identified 35 QTLs for root traits. Nine of these QTLs exhibited significant Q × E interaction effects. Taken together, our findings contribute to understanding the phenotypic and genotypic pattern of root plasticity to N deficiency, which will be useful for developing maize tolerance cultivars to N deficiency.

Monitoring the introgression of E genome chromosomes into triticale using multicolor GISH

Hybrids were made between triticale (AABBRR) line T182 and a Thinopyrum amphiploid 8801(AABBEE) and progenies advanced up to F6. Multicolor genomic in situ hybridization (McGISH) revealed different ratios of R and E genome chromosomes in each of the lines examined. R and E genome chromosomes were eliminated by F5 in two of the lines studied. The ratios of R:E genome chromosomes varied from 2:8 to 12:2 in other F6 lines. Translocations between R and E genome chromosomes were detected as early as F3. A single wheat/R translocation was detected in one line in F6.

Disaggregating polyploidy, parental genome dosage and hybridity contributions to heterosis in Arabidopsis thaliana.

Heterosis is the phenomenon whereby hybrid offspring of genetically divergent parents display superior characteristics compared with their parents. Although hybridity and polyploidy can influence heterosis in hybrid plants, the differential contributions of hybridity vs polyploidy to heterosis effects remain unknown. To address this question, we investigated heterosis effects on rosette size and growth rate of 88 distinct F1 lines of Arabidopsis thaliana consisting of diploids, reciprocal triploids and tetraploids in isogenic and hybrid genetic contexts. 'Heterosis without hybridity' effects on plant size can be generated in genetically isogenic F1 triploid plants. Paternal genome excess F1 triploids display positive heterosis, whereas maternal genome excess F1 s display negative heterosis effects. Paternal genome dosage increases plant size in F1 hybrid triploid plants by, on average, 57% (in contrast with 35% increase displayed by F1 diploid hybrids). Such effects probably derive from differential seed size, as the growth rate of triploids was similar to diploids. Tetraploid plants display a lower growth rate compared with other ploidies, whereas hybrids display increased early stage growth rate. By disaggregating heterosis effects caused by hybridity vs genome dosage, we advance our understanding of heterosis in plants and facilitate novel paternal genome dosage-based strategies to enhance heterosis effects in crop plants.

Resistance to Phakopsora pachyrhizi in Soybean PI 587905 Maps to the Rpp1 Locus and Exhibits Variable Dominance Associated with Plant Ontogeny

Soybean rust, caused by Phakopsora pachyrhizi Sydow, results in significant soybean (Glycine max (L.) Merr.) yield losses worldwide. The purpose of this research was to confirm the inheritance, gene action, and genomic location of resistance to P. pachyrhizi in soybean accession PI 587905. Two independent populations (F2-derived F3 lines and F2 plants) were inoculated with P. pachyrhizi in a greenhouse and assayed in a field, respectively, in southeastern Paraguay. Both the field F2 and the greenhouse F2-inferred segregation ratios fit the 1:2:1 ratio expected for segregation of a single gene (P > 0.05). Unlike previous studies, gene action differed according to ontogeny. Among seedlings in the greenhouse, gene action was dominant, but in the field assay among adult plants, the gene exhibited incomplete dominance. Molecular markers were used to map the resistance gene in PI 587905 to the Rpp1 locus. This information should be useful to plant breeders for developing and selecting resistant cultivars.

Abstract 1454: Patient-derived xenograft model using peritoneal fluid of gastric cancer patients

Abstract Peritoneal metastasis is the most frequent pattern of recurrence in patients with gastric cancer (GC). Patient derived xenograft (PDX) models using peritoneal fluid have been required to understand its biology and for the drug screening. So, we established the PDX model by peritoneal fluid in stage IV GC patients. First, we confirmed the preparation condition of peritoneal fluid cells for PDX model as approximately 1×107 cells in PBS. Then, we observed the engraftment rate of PDX which was 15.8% (3 of 19 patients, P2, P10 and P11). The time to 100 mm3 tumor size at F1 of 3 models was 47 ± 1, 26.7 ± 0.6 and 68 days respectively. Then, we checked the change of serial engraftment rate until F3. The more passage was progressed, the higher engraft rate was, 75% (3 of 4 mice) to 90% (9 of 10 mice) at P2, 60% (3 of 5 mice) to 85% (17 of 20 mice) at P10 and 33.3% (1 of 3 mice) to 86.7% (13 of 15 mice) at P11. In addition, time to 100mm3 tumor size of engrafted PDXs was faster at F3 than F1 in all 3 cases (41.1% in P2, 46.4% in P10 and 47.5% in P11). Also, tumor doubling time showed decreased in all engrafted PDXs according to passage (70.8% in P2, 11.5% in P10 and 71.5% in P12). Then, we checked the re-engraftment rate after thawing the frozen F3 tissue section of P2. F4 PDXs were re-engrafted 100% (3/ 3 mice) after thawing, and time to 100mm3 tumor size and tumor doubling times were not different between F3 and F4. It means that freezing and thawing of tumor fragment did not affect to engraft. After that, we compared the characterization of F0 peritoneal fluid of patient, F1∼F3 PDX tumor and the cell line established from F0. The morphologies of them were comparable by H&amp;E staining. Also, molecule expressions ofF0 to F3 and cell lines were analogous. The genetic alterations according to passages in F0 to F3 are on-going. As a result, we observed PDX from peritoneal fluid of advanced gastric cancer is feasible but various according to each patient. The PDX model by peritoneal fluid of GC patients might be helpful the biological understanding and drug development for personalized therapies. Citation Format: Jeong Min Kim, Won Suk Lee, Woo Sun Kwon, Han Na Park, Hye Rin Lee, Hyun Myong Kim, Tae Soo Kim, Hyunki Kim, Jae Kyung Roh, Hyun Cheol Chung, Sun Young Rha. Patient-derived xenograft model using peritoneal fluid of gastric cancer patients. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1454. doi:10.1158/1538-7445.AM2015-1454

QTL mapping of adult‐plant resistance to stripe rust in a ‘Lumai 21 × Jingshuang 16’ wheat population

AbstractStripe rust, caused by Puccinia striiformis f. sp. tritici, is a devastating fungal disease in common wheat (Triticum aestivum L.) worldwide. Chinese wheat cultivars ‘Lumai 21’ and ‘Jingshuang 16’ show moderate levels of adult‐plant resistance (APR) to stripe rust in the field, and they showed a mean maximum disease severity (MDS) ranging from 24 to 56.7% and 26 to 59%, respectively, across different environments. The aim of this study was to identify quantitative trait loci (QTL) for resistance to stripe rust in an F3 population of 199 lines derived from ‘Lumai 21’ × ‘Jingshuang 16’. The F3 lines were evaluated for MDS in Qingshui, Gansu province, and Chengdu, Sichuan province, in the 2009–2010 and 2010–2011 cropping seasons. Five QTL for APR were detected on chromosomes 2B (2 QTL), 2DS, 4DL and 5DS based on mean MDS in each environment and averaged values from all three environments. These QTL were designated QYr.caas‐2BS.2, QYr.caas‐2BL.2, QYr.caas‐2DS.2, QYr.caas‐4DL.2 and QYr.caas‐5DS, respectively. QYr.caas‐2DS.2 and QYr.caas‐5DS were detected in all three environments, explaining 2.3–18.2% and 5.1–18.0% of the phenotypic variance, respectively. In addition, QYr.caas‐2BS.2 and QYr.caas‐2BL.2 colocated with QTL for powdery mildew resistance reported in a previous study. These APR genes and their linked molecular markers are potentially useful for improving stripe rust and powdery mildew resistances in wheat breeding.

Using RNA Sequencing and In Silico Subtraction to Identify Resistance Gene Analog Markers for Lr16 in Wheat.

Leaf rust, caused by Puccinia triticina Eriks., is one of the most widespread diseases of wheat and breeding for resistance is one of the most effective methods of control. Lr16 is a wheat leaf rust resistance gene (R-gene) that provides resistance at both the seedling and adult stages. Simple-sequence repeat (SSR) markers have been used to map Lr16 to the distal end of chromosome 2B. The objectives of this study were to use RNA sequencing (RNA-seq) and in silico subtraction to identify new R-gene analogs (RGAs) and use them as Lr16 markers. RNA was isolated from the susceptible wheat cultivar Thatcher (Tc) and the resistant Tc isolines TcLr10, TcLr16, TcLr21, and sequenced using Illumina technology. Using in silico subtraction, sequences from the resistant Tc isolines were aligned to a Tc reference expressed sequence tag (EST) set. Sequences not aligning to the Tc reference were assembled into contigs and analyzed using BLASTx to determine putative gene functions. Primer pairs were designed for 181 RGA sequences, of which, 137 amplified in at least one of the parents. A mapping population was developed with 165 F2 lines from a cross between the rust-susceptible cultivar Chinese Spring (CS) and TcLr16. Two RGA markers XTaLr16_RGA266585 and XTaLr16_RGA22128 were identified that mapped proximally 1.2 and 23.8 cM from Lr16, respectively. Three SSR markers Xwmc764, Xwmc661, and Xbarc35 mapped between these two RGA markers at distances of 5.0, 10.9, and 16.1 cM from Lr16, respectively. In silico subtraction is an effective technique for isolating RGAs linked to R-genes of interest.