Σχεδιασμός και κατασκευή Μαγνητομέτρου Πύλης Ροής

Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Συστήματα Αυτοματισμού

Interoperability Challenges in the Cybersecurity Information Sharing Ecosystem

Threat intelligence helps businesses and organisations make the right decisions in their fight against cyber threats, and strategically design their digital defences for an optimised and up-to-date security situation. Combined with advanced security analysis, threat intelligence helps reduce the time between the detection of an attack and its containment. This is achieved by continuously providing information, accompanied by data, on existing and emerging cyber threats and vulnerabilities affecting corporate networks. This paper addresses challenges that organisations are bound to face when they decide to invest in effective and interoperable cybersecurity information sharing and categorises them in a layered model. Based on this, it provides an evaluation of existing sources that share cybersecurity information. The aim of this research is to help organisations improve their cyber threat information exchange capabilities, to enhance their security posture and be more prepared against emerging threats

Identification und characterization of a new class of highly conserved non-coding sequences in plants

Ultraconserved elements (UCEs), DNA sequences, which are 100% identical between mammalian genomes are enigmatic features whose function is not well understood. UCEs are under strong purifying selection and a number of biological functions have been proposed to explain their robust conservation, such as gene regulation, RNA processing, and maintaining genome integrity. However, all these functions are evolutionary tolerant to DNA sequence divergence without affecting their sequence specific interactions. Here, we report the identification and characterization of highly conserved noncoding sequences in plant genomes. We have identified them after whole genome comparison studies between Arabidopsis thaliana (mouse-ear cress) and Vitis vinifera (grapevine). Arabidopsis and Vitis have diverged from their common ancestor ~115 Mya, allowing significant changes at the DNA sequence level to occur. We found 36 elements, which are >55 bp long and share at least 85% sequence identity. Interestingly, these elements exhibit properties similar to the mammalian UCEs, such that we named them UCE-like elements (ULEs). In addition to sequence constraints our data indicate that ULEs are functional elements. Further analysis showed that ULEs are under strong purifying selection. All of them have a sharp drop of A-T content just at their borders, and they are enriched next to genes involved in development. Intriguingly, the latter show preferential expression in undifferentiated cells. By comparing the genomes of Brachypodium distachyon (purple false brome) and Oryza sativa (rice), species that diverged ~50 Mya, we identified a different set of ULEs with similar properties in monocotyledons. Surprisingly, as their animal counterparts, ULEs are depleted from segmental duplications. This observation led to the suggestion that ULEs or the regions that contain them are dosage sensitive. Our hypothesis about the function of ULEs is that they serve as agents of chromosome copy counting. According to this hypothesis, the two homologous ULEs may compare their sequence perhaps through chromosome pairing to ensure the exact number of chromosomes. We employed a cytogenetic approach, fluorescence in situ hybridization (FISH), and found evidence that ULE regions exhibit increased pairing frequency in somatic cells relative to regions that are depleted from ULEs. We further investigated the potential dosage-sensitive nature of ULEs. Perturbation of one ULE resulted in distorted transmission efficiency of the corresponding allele in the offspring. Conversely, transmission efficiency of the same mutant was not distorted in an aneuploid context. Moreover, addition of four extra copies of ULEs did not yield any obvious phenotypes. Further investigation remains necessary to confirm a general role of ULEs in surveying genome dosage and integrity

Identification and Characterization of a New Class of Highly Conserved Non-Coding Sequences in Plants

Ultraconserved elements (UCEs), DNA sequences, which are 100% identical between mammalian genomes are enigmatic features whose function is not well understood. UCEs are under strong purifying selection and a number of biological functions have been proposed to explain their robust conservation, such as gene regulation, RNA processing, and maintaining genome integrity. However, all these functions are evolutionary tolerant to DNA sequence divergence without affecting their sequence specific interactions. Here, we report the identification and characterization of highly conserved noncoding sequences in plant genomes. We have identified them after whole genome comparison studies between Arabidopsis thaliana (mouse-ear cress) and Vitis vinifera (grapevine). Arabidopsis and Vitis have diverged from their common ancestor ~115 Mya, allowing significant changes at the DNA sequence level to occur. We found 36 elements, which are >55 bp long and share at least 85% sequence identity. Interestingly, these elements exhibit properties similar to the mammalian UCEs, such that we named them UCE-like elements (ULEs). In addition to sequence constraints our data indicate that ULEs are functional elements. Further analysis showed that ULEs are under strong purifying selection. All of them have a sharp drop of A-T content just at their borders, and they are enriched next to genes involved in development. Intriguingly, the latter show preferential expression in undifferentiated cells. By comparing the genomes of Brachypodium distachyon (purple false brome) and Oryza sativa (rice), species that diverged ~50 Mya, we identified a different set of ULEs with similar properties in monocotyledons. Surprisingly, as their animal counterparts, ULEs are depleted from segmental duplications. This observation led to the suggestion that ULEs or the regions that contain them are dosage sensitive. Our hypothesis about the function of ULEs is that they serve as agents of chromosome copy counting. According to this hypothesis, the two homologous ULEs may compare their sequence perhaps through chromosome pairing to ensure the exact number of chromosomes. We employed a cytogenetic approach, fluorescence in situ hybridization (FISH), and found evidence that ULE regions exhibit increased pairing frequency in somatic cells relative to regions that are depleted from ULEs. We further investigated the potential dosage-sensitive nature of ULEs. Perturbation of one ULE resulted in distorted transmission efficiency of the corresponding allele in the offspring. Conversely, transmission efficiency of the same mutant was not distorted in an aneuploid context. Moreover, addition of four extra copies of ULEs did not yield any obvious phenotypes. Further investigation remains necessary to confirm a general role of ULEs in surveying genome dosage and integrity

Disruption of the pollen-expressed FERONIA homologs ANXUR1 and ANXUR2 triggers pollen tube discharge

The precise delivery of male to female gametes during reproduction in eukaryotes requires complex signal exchanges and a flawless communication between male and female tissues. In angiosperms, molecular mechanisms have recently been revealed that are crucial for the dialog between male (pollen tube) and female gametophytes required for successful sperm delivery. When pollen tubes reach the female gametophyte, they arrest growth, burst and discharge their sperm cells. These processes are under the control of the female gametophyte via the receptor-like serine-threonine kinase (RLK) FERONIA (FER). However, the male signaling components that control the sperm delivery remain elusive. Here, we show that ANXUR1 and ANXUR2 (ANX1, ANX2), which encode the closest homologs of the FER-RLK in Arabidopsis, are preferentially expressed in pollen. Moreover, ANX1-YFP and ANX2-YFP fusion proteins display polar localization to the plasma membrane at the tip of the pollen tube. Finally, genetic analyses demonstrate that ANX1 and ANX2 function redundantly to control the timing of pollen tube discharge as anx1 anx2 double-mutant pollen tubes cease their growth and burst in vitro and fail to reach the female gametophytes in vivo. We propose that ANX-RLKs constitutively inhibit pollen tube rupture and sperm discharge at the tip of growing pollen tubes to sustain their growth within maternal tissues until they reach the female gametophytes. Upon arrival, the female FER-dependent signaling cascade is activated to mediate pollen tube reception and fertilization, while male ANX-dependent signaling is deactivated, enabling the pollen tube to rupture and deliver its sperm cells to effect fertilization

Computational analysis and characterization of UCE-like elements (ULEs) in plant genomes

Ultraconserved elements (UCEs), stretches of DNA that are identical between distantly related species, are enigmatic genomic features whose function is not well understood. First identified and characterized in mammals, UCEs have been proposed to play important roles in gene regulation, RNA processing, and maintaining genome integrity. However, because all of these functions can tolerate some sequence variation, their ultraconserved and ultraselected nature is not explained. We investigated whether there are highly conserved DNA elements without genic function in distantly related plant genomes. We compared the genomes of Arabidopsis thaliana and Vitis vinifera; species that diverged ∼115 million years ago (Mya). We identified 36 highly conserved elements with at least 85% similarity that are longer than 55 bp. Interestingly, these elements exhibit properties similar to mammalian UCEs, such that we named them UCE-like elements (ULEs). ULEs are located in intergenic or intronic regions and are depleted from segmental duplications. Like UCEs, ULEs are under strong purifying selection, suggesting a functional role for these elements. As their mammalian counterparts, ULEs show a sharp drop of A+T content at their borders and are enriched close to genes encoding transcription factors and genes involved in development, the latter showing preferential expression in undifferentiated tissues. By comparing the genomes of Brachypodium distachyon and Oryza sativa, species that diverged ∼50 Mya, we identified a different set of ULEs with similar properties in monocots. The identification of ULEs in plant genomes offers new opportunities to study their possible roles in genome function, integrity, and regulation