We developed the bitterling as a unique, well-studied model organism in the area of the evolutionary ecology of brood parasitism. The bitterling-mussel relationship, interspecific mussel host... Show moreWe developed the bitterling as a unique, well-studied model organism in the area of the evolutionary ecology of brood parasitism. The bitterling-mussel relationship, interspecific mussel host preference, and mussel gill structure are studied in detail, to help understand the developmental adaptation of bitterling embryos in response to their mussel hosts. Our complete stage series of the bitterling species R. ocellatus in Chapter 2 is a new, character-based systems that are compatible with the widely-used zebrafish staging system. With time-lapse video, we demonstrated the dynamic processes of hatching moment of the rosy bitterling in real time, which indicates the hatching process is mechanical rather than enzymatic. In Chapter 3, we described the neuroanatomy of bitterling for the first time, filling the gaps in the previous embryonic research in various bitterling taxa. Combined with the molecular analysis of brain early development in Chapter 4, brain development in the rosy bitterling is compared with that in the zebrafish. In Chapter 5, we studied the morphogenetic process of blastokinesis in the bitterling embryo, and its possible relation to brood parasitism. Show less
Cells communicate in multicellular organisms; by secreting and sensing signals, in order to adjust their behavior to the environment. Extracellular signals such as cytokines and growth factors bind... Show moreCells communicate in multicellular organisms; by secreting and sensing signals, in order to adjust their behavior to the environment. Extracellular signals such as cytokines and growth factors bind to cell surface receptors and trigger the activation of multiple protein signal transduction cascades that mediate cellular responses such as proliferation, differentiation, apoptosis and motility. The Mitogen-activated protein kinase (MAPK) family is a group of homologous proteins forming several linear signal transduction pathways. The MAPK family is conserved among eukaryotes and most vertebrates contain at least 14 MAPKs. We are interested in the molecular mechanisms of MAPK signalling that facilitate proper development of the zebrafish embryo. The zebrafish is an excellent model to delineate MAPK associated embryonic processes. The bodyplan is completed within 24hours and within a week most organs are formed. With the current available zebrafish tools molecular mechanisms could be identified and linked to cellular processes and morphological observations. We constructed constitutive active zebrafish Erk2 mutants for identification of new signalling events. We completed expression analysis of all P38 isoforms by expression analysis of the P38_ and P38_ isoforms. We also performed a comparative study between P38_ and Erk2 MAPK in gastrulation. Finally, We addressed the role of P38_ in zebrafish angiogenesis. Show less
Multiple processes are influenced by a protein family named the function of Mitogen Activated Protein Kinases (MAPK), where among tissue morphogenesis, cell-proliferation, cell-differentiation,... Show moreMultiple processes are influenced by a protein family named the function of Mitogen Activated Protein Kinases (MAPK), where among tissue morphogenesis, cell-proliferation, cell-differentiation, cell-survival and immune reactions. A consequence of this broad role of these proteins is that disturbed MAPK signaling possibly leads to severe affects, and could even lead to the development of a disease or disturb embryogenesis. The human genome encodes for 14 mapk genes. One of the best characterized MAPK signaling transductions pathways is the Extracellular signal Regulated Kinase 1 and 2 (ERK1/ERK2). The zebrafish is a relatively new, genetic accessible model organism, which is because of their transparency of the embryos, very suitable to study the role of the MAPKs in embryonic development. The study described in this thesis shows that the zebrafish genome encodes for the same mapk genes, which makes it possible to study the functions of these proteins, using the zebrafish. Further investigations to the roles of ERK1 and ERK2 during embryonic development led to the new insight that ERK1 and ERK2 have distinct roles during crucial developmental cell migration processes and the differentiation of tissues and cell types. In addition, it was found that ERK1 and ERK2 affect the expression of common as well as distinct target genes. Show less
Barley androgenesis represents an attractive system to study stress-induced cell differentiation and is a valuable tool for efficient plant breeding. The switch from the pollen developmental... Show moreBarley androgenesis represents an attractive system to study stress-induced cell differentiation and is a valuable tool for efficient plant breeding. The switch from the pollen developmental pathway towards an androgenic route involves several well-described morphological changes. However, little is known about the pathways leading to embryo formation and about the transcriptome of androgenic microspores. The research described in this thesis aimed to identify new "bio-markers" for barley androgenesis induction and embryo development. The concept of a "bio-marker" is not a single gene, protein, metabolite or phenotype. It refers to the concept of understanding biological events, such as gene expression profiles or morphological changes at certain biological states. The work presented in this thesis has provided a substantial contribution towards understanding the mechanisms of androgenesis induction.The use of a cell tracking system in combination with biochemical markers has been crucial in pointing out that the morphology of embryogenic microspores, and in identifying programmed cell death as an integral part of the developmental pathway of androgenic embryos. In addition, the markers identified in this thesis by cDNA array and 14-3-3 expression analyses represent useful tools for further analysis of stress-induced androgenesis and pattern formation in androgenic embryos. Understanding the role of these markers, as well as the role of programmed cell death during exine wall rupture and subsequent pattern formation represents a future challenge for the improvement of quality and yield of androgenic embryos. Show less
