Constrained Supersymmetric Flipped SU(5) GUT Phenomenology

We explore the phenomenology of the minimal supersymmetric flipped SU(5) GUT model (CFSU(5)), whose soft supersymmetry-breaking (SSB) mass parameters are constrained to be universal at some input scale, $M_{in}$, above the GUT scale, $M_{GUT}$. We analyze the parameter space of CFSU(5) assuming that the lightest supersymmetric particle (LSP) provides the cosmological cold dark matter, paying careful attention to the matching of parameters at the GUT scale. We first display some specific examples of the evolutions of the SSB parameters that exhibit some generic features. Specifically, we note that the relationship between the masses of the lightest neutralino and the lighter stau is sensitive to $M_{in}$, as is the relationship between the neutralino mass and the masses of the heavier Higgs bosons. For these reasons, prominent features in generic $(m_{1/2}, m_0)$ planes such as coannihilation strips and rapid-annihilation funnels are also sensitive to $M_{in}$, as we illustrate for several cases with tan(beta)=10 and 55. However, these features do not necessarily disappear at large $M_{in}$, unlike the case in the minimal conventional SU(5) GUT. Our results are relatively insensitive to neutrino masses.Comment: 23 pages, 8 figures; (v2) added explanations and corrected typos, version to appear in EPJ

Molecular Characterization Of The Barley Fr-H2 QT Locus

Frost resistance-H2 is major quantitative trait locus that, in combination with VRN-H1/Fr-H1, affects freezing tolerance of barley. Mapping coincident with Fr-H2 are QTLs regulating COR proteins accumulation and a cluster of more than 14 genes encoding CBF transcription factors – at present the best candidates to explain the effects given by the locus. Expression analyses, conducted on a ‘Nure’ x ‘Tremois’ barley mapping population segregating for VRN-H1/Fr-H1 and Fr-H2, revealed that transcript levels of all cold-induced CBF genes at Fr-H2 were significantly higher in recombinants harboring the vrn-H1 winter allele than in recombinants harboring the Vrn-H1 spring allele. Also, steady-state HvCBF2 and HvCBF4 levels were significantly higher in recombinants harboring the Nure allele at Fr-H2. In a positional cloning effort, a large mapping population consisting of more than 3,698 meiotic events was used to fine map Fr-H2. Recombinants between 12 CBF genes under Fr-H2 have been identified in a total genetic distance of 0.81 cM. The few recombinants between the different HvCBF sub-clusters were chosen and taken to homozygosity in order to separate the effects of the single HvCBF genes. At the same time, a PCR-based screening strategy of the genomic BAC library of cv ‘Morex’ was undertaken, and selected clones assembled into contigs through high information content fingerprinting (HICF). BAC-end sequencing is being used to close remaining gaps and to create anchor points between the genetic and physical maps of the region. Alignment of the genetically colinear region of ‘Nure’ against ‘Tremois’, alongside ‘Dicktoo’ and ‘Morex’, revealed several key molecular differences that we hypothesize accounts for the nature of Fr-H2. The likely scenario is that both a ‘structural’ and a ‘regulatory’ component act together to enhance the tolerance. The first component could be likely due to either allelic or number variation of HvCBF genes at Fr-H2 where “more” CBFs could be better, while the second one would be due to the winter allele of VRN-H1/Fr-H1

Mapping regulatory genes as candidates for cold and drought stress tolerance in barley

Cereal crop yield is greatly affected in many growing areas by abiotic stresses, mainly low temperature and drought. In order to find candidates for the tolerance genes for these stresses, 13 genes encoding for transcription factors and upstream regulators were screened by amplification and SSCP on six parental genotypes of three barley mapping populations ('Nure' x 'Tremois', 'Proctor' x 'Nudinka', and 'Steptoe' x 'Morex'), and mapped as newly developed STS, SNP, and SSCP markers. A new consensus function map was then drawn using the three maps above, including 16 regulatory candidate genes (CGs). The positions of barley cold and drought tolerance quantitative trait loci (QTLs) presently described in the literature were added to the consensus map to find positional candidates from among the mapped genes. A cluster of six HvCBF genes co-mapped with the Fr-H2 cold tolerance QTL, while no QTLs for the same trait were positioned on chromosome 7H, where two putative barley regulators of CBF expression, ICE1 and FRY1, found by homology search, were mapped in this work. These observations suggest that CBF gene(s) themselves, rather than their two regulators, are at present the best candidates for cold tolerance. Four out of 12 drought tolerance QTLs of the consensus map are associated with regulatory CGs, on chromosomes 2H, 5H, and 7H, and two QTLs with effector genes, on chromosomes 5H and 6H. The results obtained could be used to guide MAS applications, allowing introduction into an ideal genotype of favourable alleles of tolerance QTLs

Fine mapping of a HvCBF gene cluster at the frost resistance locus Fr-H2 in barley.

Barley is an economically important model for the Triticeae tribe. We recently developed a new resource: the ‘Nure’ x ‘Tremois’ mapping population. Two low temperature QTLs were found to segregate on the long arm of chromosome 5H (Fr-H1, distal; Fr-H2, proximal). With the final aim of positional cloning of the genetic determinants of Fr-H1 and Fr-H2, a large segregating population of 1,849 F2 plants between parents ‘Nure’ and ‘Tremois’ was prepared. These two QT loci were first validated by using a set of F3 families, marker-selected to harbor pairs of reciprocal haplotypes, with one QTL fixed at homozygosity and the alternate one in heterozygous phase. The study was then focused towards the isolation of the determinant of Fr-H2. Subsequent recombinant screens and phenotypic evaluation of F4 segregants allowed us to estimate (P < 0.01) a refinedgenomic interval of Fr-H2 (4.6 cM). Several barley genes with the CBF transcription factor signature had been already roughly mapped in cluster at Fr-H2, and they representlikely candidate genes underlying this QTL. Using the large segregating population (3,698 gametes) a high-resolution genetic map of the HvCBF gene cluster was then constructed, and after fine mapping, six recombinations between the HvCBFs were observed. It was therefore possible to genetically divide seven HvCBF subclusters in barley, in a region spanning 0.81 cM, with distances among them varying from 0.03 to 0.32 cM. The few recombinants between the different HvCBF subclusters are being marker selected and taken to homozygosity, to phenotypically separate the effects of the single HvCBF genes