Exploring Cosmology and Structure Formation via High-z Galaxies

This thesis exploits the large-scale structure of the Universe via observations over a wide redshift range, with the aim of constraining the current cosmological models and galaxy formation physics. We present the eXtreme Multiplex Spectrograph (XMS), a proposed spectrograph that can map simultaneously 4000 Emission Line Galaxies (ELGs) and Luminous Red Galaxies (LRGs) in the range 0.4 ≤ z ≤ 0.8, with a success rate of 88%. Figures of merit clearly indicate that XMS is better or even competitive compared to future surveys for measurements of the gravitational growth rate, Baryon Acoustic Oscillations (BAO) and dark-matter halo mass function. Next, by selecting a unique photometric sample of 130, 000 LRGs in the Sloan Digital Sky Survey (SDSS) Stripe 82, with an estimated average redshift z ∼ 1, we perform a clustering analysis and compare the clustering evolution of the high-z Stripe 82 LRGs to lower-z LRGs. An immediate feature of the Stripe 82 LRGs clustering is a power excess at large scales. This behaviour is not expected within the ΛCDM model, making the conclusion of a slow clustering evolution as observed for the lower-z LRGs, non-trivial. Only Non-Gaussian models are able to describe the large scale clustering of the Stripe 82 LRGs. From follow up spectroscopic observations of a subsample of the Stripe 82 LRGs, we confirm that the average red- shift of our sample is z ∼ 0.9, while the slow clustering evolution of the LRGs is now slightly more favoured. However, Non-Gaussianity is still detected at a 2σ level. Finally, from the largest and deepest near-infrared field to present, the UltraVISTA survey, we select ≈ 4000 Distant Red Galaxies (DRGs) and study the largest galaxy separations ever probed with these massive galaxies. In agreement with previous results, UltraVISTA DRGs are strongly clustered objects. Furthermore, they show stronger clustering within their brighter K-limited samples, that could possibly imply luminosity segregation. Their connection to the local descendants cannot yet be established

Introducing Green, Eco-Friendly Practices and Circular Economy Principles in Vocational Education Through a Novel Analysis-Synthesis Method: Design, Implementation and Evaluation

Purpose: A novel, Project- and Collaborative Learning-based educational method is proposed, implemented and evaluated in this paper. The aim is to exploit hands-on laboratory modules in Vocational Education in order to experientially introduce students to green, eco-friendly practices and the principles of sustainability and circular economy. Besides their apparent individual and social benefits, such knowledge and skills are also expected to raise qualifications and employability of Vocational Education graduates. Methods: The proposed method is tested through a quasi-experimental methodology, via an educational intervention with a class of Vocational Lyceum students, in the field of Electrical and Electronics Engineering. The learning content focuses on the reclaiming and reuse of operational components from damaged electrical/electronic equipment at end-of-life stage. Through repeated Analysis and Synthesis phases, students learn to extract, measure, classify and reuse operational components either to repair similar equipment or to design and construct novel devices. Results: Evaluation is carried out via closed and open type activities as well as by observation sheets of the teacher. Learning outcomes are evaluated through knowledge post-tests of the closed type while social/emotional outcomes are evaluated through questionnaires. Evaluation results indicate that the proposed method does produce cognitive and social/emotional skills gains for the students. The development of metacognitive skills and the stimulation of imagination and innovative thinking in the students is also observed by the teacher, but not formally evaluated due to practical constraints. Conclusions: The proposed method is implemented and pilot-tested with positive results both as to the cognitive and as to the social/emotional domain - yet, these results are of an indicative value, due to the limited scale of the educational intervention. Future research is necessary in order to evaluate the proposed method in extent and possibly compare results across education grades or engineering fields, as the method is generic enough to be easily adaptable for different ages/grades and engineering/technical fields of study

Structural Diversity and Highly Specific Host-Pathogen Transcriptional Regulation of Defensin Genes Is Revealed in Tomato

Defensins are small and rather ubiquitous cysteine-rich anti-microbial peptides. These proteins may act against pathogenic microorganisms either directly (by binding and disrupting membranes) or indirectly (as signaling molecules that participate in the organization of the cellular defense). Even though defensins are widespread across eukaryotes, still, extensive nucleotide and amino acid dissimilarities hamper the elucidation of their response to stimuli and mode of function. In the current study, we screened the Solanum lycopersicum genome for the identification of defensin genes, predicted the relating protein structures, and further studied their transcriptional responses to biotic (Verticillium dahliae, Meloidogyne javanica, Cucumber Mosaic Virus, and Potato Virus Y infections) and abiotic (cold stress) stimuli. Tomato defensin sequences were classified into two groups (C8 and C12). Our data indicate that the transcription of defensin coding genes primarily depends on the specific pathogen recognition patterns of V. dahliae and M. javanica. The immunodetection of plant defensin 1 protein was achieved only in the roots of plants inoculated with V. dahliae. In contrast, the almost null effects of viral infections and cold stress, and the failure to substantially induce the gene transcription suggest that these factors are probably not primarily targeted by the tomato defensin network

Evolutionary relationships among Avena species and studies on genomic changes in interspecific Avena hybrids by using repetitive sequences

[…] Ο σκοπός αυτής της διδακτορικής μελέτης είναι η χρήση των νουκλεοτιδικών δεδομένων των ριβοσωμικών αλληλουχιών σε μια προσπάθεια να αναγνωριστούν είδη με πιθανό ρόλο στην εξέλιξη των πολυπλοειδών. Επιπλέον, στόχος της παρούσας εργασίας είναι και η ανάλυση συνθετικών και φυσικών διειδικών υβριδίων του γένους Avena (F₁ και F₂ γενιάς) και των γονέων τους, τόσο κυτταρογενετικά όσο και με τις τεχνικές των AFLP και RAPD για να καταγραφούν οι γονιδιωματικές μεταβολές που αυτά υφίστανται. Επιπροσθέτως ως μέρος μίας ευρείας ανάλυσης του γονιδιώματος, διερευνάται η επίπτωση του υβριδισμού στον αριθμό των rRNA αντιγράφων και του μεγέθους του γονιδιώματος των υβριδίων με την τεχνική της ποσοτικής PCR και με τις μετρήσεις πυρηνικού περιεχομένου (C-values), αντίστοιχα

The origin of the C-genome and cytoplasm of Avena polyploids

The contribution of C-genome diploid species to the evolution of polyploid oats was studied using C-genome ITS-specific primers. SCAR analysis among Avena accessions confirmed the presence of C-genome ITS1-5.8S-ITS2 sequences in the genome of AACC and AACCDD polyploids. In situ hybridization and screening of more than a thousand rRNA clones in Avena polyploid species containing the C-genome revealed substantial C-genome rRNA sequence elimination. C-genome clones sequenced and Maximum Likelihood Parsimony analysis revealed close proximity to Avena ventricosa ITS1-5.8S-ITS2 sequences, providing strong evidence of the latter's active role in the evolution of tetraploid and hexaploid oats. In addition, cloning and sequencing of the chloroplastic trnL intron among the most representative Avena species verified the maternal origin of A-genome for the AACC interspecific hybrid formation, which was the genetic bridge for the establishment of cultivated hexaploid oats

Comparative molecular and cytogenetic methods can clarify meiotic incongruities in Avena allopolyploid hybrids

Avena longiglumis is a diploid species that has been proposed as the A-genome donor of allopolyploid oats. In order to clarify its participation in the evolution of oats, a triploid A. magna × A. longiglumis hybrid was synthesized and studied, via a concurrent combination of cytogenetic and molecular techniques. The analysis of pollen mother cells revealed that synapsis percentage and chromosome chiasmata per cell were low; still they were the highest recorded among the diploid species used as pollinators of AC-genome tetraploids. In addition, genomic in situ hybridization revealed extensive chromosomal translocations among the allopolyploids that may have contributed to the low chromosomal affinity. Furthermore, amplified fragment length polymorphisms revealed the extensive genomic modifications that followed the interspecific hybridization, depicted mainly as the loss of parental bands (51.29%) and the creation of novel bands in the progeny (15.73%). As a result, the combination of cytogenetic and molecular techniques can elucidate meiotic incongruities that can make the unraveling of oat evolution challenging

Genetic relatedness among cultivars of the greek plum germplasm

Genetic diversity of the Greek plum germplasm collection was investigated using a combined RAPD and ISSR molecular markers approach. Twenty-six genotypes held at NAGREF-Naoussa were analyzed, producing in total 150 loci, of which 116 were polymorphic. Both techniques were highly informative and had a discrimination power greater than 0.9. RAPD and ISSR dendrograms were fairly correlated. The accessions were clustered according to ploidy and species. All Prunus domestica genotypes were grouped together and showed greater similarity to P. insititia and P. cerasifera genotypes compared to P. salicina, which was found genetically diverged. Bayesian structural analysis revealed significant admixture among genotypes. Greek varieties P. domestica 'Goulina' and 'Asvestochoriou' exhibited a distinctive genetic background, differentiating them from foreign varieties. This feature could make them attractive for breeding programs, since they can increase genetic diversity

Genetic relatedness among cultivars of the greek plum germplasm

Genetic diversity of the Greek plum germplasm collection was investigated using a combined RAPD and ISSR molecular markers approach. Twenty-six genotypes held at NAGREF-Naoussa were analyzed, producing in total 150 loci, of which 116 were polymorphic. Both techniques were highly informative and had a discrimination power greater than 0.9. RAPD and ISSR dendrograms were fairly correlated. The accessions were clustered according to ploidy and species. All Prunus domestica genotypes were grouped together and showed greater similarity to P. insititia and P. cerasifera genotypes compared to P. salicina, which was found genetically diverged. Bayesian structural analysis revealed significant admixture among genotypes. Greek varieties P. domestica 'Goulina' and 'Asvestochoriou' exhibited a distinctive genetic background, differentiating them from foreign varieties. This feature could make them attractive for breeding programs, since they can increase genetic diversity

Screening A. ventricosa populations for 2n gametes

Sexual polyploidization via the formation of 2n gametes has been acknowledged as the most significant evolutionary mode of polyploidization among plant species. The present study was conducted in order to determine whether 2n gametes are present in the C-genome diploid Avena ventricosa Bal. ex Coss., a species that contributed to the evolution of the cultivated hexaploid species (Avena sativa L). Individual plants belonging to four different Cypriot populations, were screened for pollen grain size variation with the aim to distinguish 2n gametes. Avena ventricosa ARI00-845 was identified to produce large pollen grains at a low percentage (1.21%). Subsequent analysis using flow cytometry confirmed the presence of 2n gametes in the pollen. Cytogenetic analyses of pollen mother cells revealed cells with twice the typical chromosome number at metaphase I (i.e., 28 chromosomes). We postulate that irregularities in cell wall formation preceding meiosis could have contributed to the mode of chromosome doubling

Structural patterns and genetic diversity among oat (Avena) landraces assessed by microsatellite markers and morphological analysis

As a counterweight to genetic erosion, landraces could become important germplasm resources for breeding. In the present study the genetic diversity of 62 Greek and Eastern European oat accessions (seven cultivars and 55 common and red oat landraces collected from 1904 to 1960) was studied using simple sequence repeats and 31 morphological descriptors. High levels of polymorphism were detected and 209 distinctive alleles were identified; on average 14.65 alleles per primer. Both, the principal component analysis derived from the morphological data, and the unweighted pair group method with arithmetic mean from the molecular analysis clustered the oat genotypes according to their type (common and red oats). In addition, the analysis of molecular variation showed that there were noteworthy differences within designated geographic regions. Moreover, a more discrete subpopulation structure was identified based on allele frequency using a Bayesian clustering approach. A clear distinction was evident among the red and common oats suggesting that they should be considered as separate species