@phdthesis{vonMeyer2021,
  author    = {von Meyer, Katharina},
  title     = {Molecular characterization of defensin-like proteins in the fertilization process of \(Nicotiana\) \(tabacum\)},
  doi       = {10.25972/OPUS-19214},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-192141},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {Flowering plants or angiosperms have developed a fertilization mechanism that involves a female egg and central cell, as well as two male sperm cells. A male gametophyte carries the two non-mobile sperm cells, as they need to be delivered to the female gametophyte, the embryo sac. This transport is initiated by a pollen grain that is transmitted onto the stigma of the angiosperm flower. Here it hydrates, germinates, and forms a pollen tube, which navigates through the female plant tissue towards the ovary. The pollen tube grows into an ovule through the funiculus and into one of the two synergid cells. There, growth arrests and the pollen tube bursts, releasing the two sperm cells. One of the sperm cells fuses with the egg cell, giving rise to the embryo, the other one fuses with the central cell, developing into the endosperm, which nourishes the embryo during its development. After a successful fertilization, each ovule develops into a seed and a fruit is formed. This usually consists of several fertilized ovules. The directional growth of the pollen tube through the maternal tissues towards the ovule, as well as sperm cell release, requires a complex communication between the male and the female gametophyte to achieve reproductive success. Over the last years many studies have been performed, contributing to the understanding of cell-cell communication events between the two gametophytes, nevertheless still many aspects remain to be elucidated. This work focused on two topics: i.) Analysis of biological processes affected by pollination and fertilization in the Nicotiana tabacum flower and identification of cysteine rich proteins (CRPs) expressed via isolating and sequencing RNA from the tissue and analyzing the resulting data. ii.) Identification of the defensin-like protein (DEFL) responsible for pollen tube attraction towards the ovule in tobacco. First, tissue samples of pollen tubes and mature ovules were taken at different stages of the fertilization process (unpollinated ovules, after pollination, and after fertilization of the flower). RNA was then isolated and a transcriptome was created. The resulting reads were assembled and transcriptome data analysis was performed. Results showed that pollen tubes and mature ovules differ severely from each other, only sharing about 23 \% of the transcripts, indicating that different biological processes are dominant in the two gametophytes. A MapMan analysis revealed that in the pollen tube the most relevant biological processes are related to the cell wall, signaling, and transport, which supports the fact that the pollen tube grows fast to reach the ovule. On the other hand, in the ovule the values of highest significance were obtained for processes related to protein synthesis and regulation. Upon comparing the transcripts in the ovule before and after pollination, as well as after fertilization, it showed that pollination of the flower causes a bigger alteration in the ovule on the transcriptomic level compared to the step from pollination to fertilization. A total of 953 CRPs were identified in Nicotiana tabacum, including 116 DEFLs. Among those, the peptide responsible for pollen tube attraction towards the ovule should be found. Based on in-silico analysis four candidate peptides were chosen for further analysis, two of which had increased expression levels upon pollination and fertilization and the other two displayed an opposite expression. Quantitative real time PCR experiments were performed for the candidates, confirming the in-silico data in vivo. The candidate transcripts were then expressed in a cell free system and applied to pollen tubes in order to test their effect on the growing cells. Positive controls were used, where pollen tubes grew towards freshly dissected ovules. The four candidates did not provoke a pollen tube attraction towards the peptide, leaving open the chance to work on the 112 remaining DEFLs in the future.},
  subject      = {Samenpflanzen},
  language  = {en}
}
@article{BoehmScherzerKroletal.2016,
  author    = {B{\"o}hm, Jennifer and Scherzer, S{\"o}nke and Krol, Elzbieta and Kreuzer, Ines and von Meyer, Katharina and Lorey, Christian and Mueller, Thomas D. and Shabala, Lana and Monte, Isabel and Salano, Roberto and Al-Rasheid, Khaled A. S. and Rennenberg, Heinz and Shabala, Sergey and Neher, Erwin and Hedrich, Rainer},
  title     = {The Venus Flytrap Dionaea muscipula Counts Prey-Induced Action Potentials to Induce Sodium Uptake},
  series = {Current Biology},
  volume    = {26},
  journal   = {Current Biology},
  number    = {3},
  doi       = {10.1016/j.cub.2015.11.057},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-128054},
  pages     = {286-295},
  year      = {2016},
  abstract  = {Carnivorous plants, such as the Venus flytrap (Dionaea muscipula), depend on an animal diet when grown in nutrient-poor soils. When an insect visits the trap and tilts the mechanosensors on the inner surface, action potentials (APs) are fired. After a moving object elicits two APs, the trap snaps shut, encaging the victim. Panicking preys repeatedly touch the trigger hairs over the subsequent hours, leading to a hermetically closed trap, which via the gland-based endocrine system is flooded by a prey-decomposing acidic enzyme cocktail. Here, we asked the question as to how many times trigger hairs have to be stimulated (e.g., now many APs are required) for the flytrap to recognize an encaged object as potential food, thus making it worthwhile activating the glands. By applying a series of trigger-hair stimulations, we found that the touch hormone jasmonic acid (JA) signaling pathway is activated after the second stimulus, while more than three APs are required to trigger an expression of genes encoding prey-degrading hydrolases, and that this expression is proportional to the number of mechanical stimulations. A decomposing animal contains a sodium load, and we have found that these sodium ions enter the capture organ via glands. We identified a flytrap sodium channel DmHKT1 as responsible for this sodium acquisition, with the number of transcripts expressed being dependent on the number of mechano-electric stimulations. Hence, the number of APs a victim triggers while trying to break out of the trap identifies the moving prey as a struggling Na+-rich animal and nutrition for the plant.},
  subject      = {Venusfliegenfalle},
  language  = {en}
}
@article{BoehmScherzerKroletal.2016,
  author    = {B{\"o}hm, Jennifer and Scherzer, S{\"o}nke and Krol, Elzbieta and Kreuzer, Ines and von Meyer, Katharina and Lorey, Christian and Mueller, Thomas D. and Shabala, Lana and Monte, Isabel and Solano, Roberto and Al-Rasheid, Khaled A. S. and Rennenberg, Heinz and Shabala, Sergey and Neher, Erwin and Hedrich, Rainer},
  title     = {The Venus flytrap Dionaea muscipula counts prey-induced action potentials to induce sodium uptake},
  series = {Current Biology},
  volume    = {26},
  journal   = {Current Biology},
  number    = {3},
  doi       = {10.1016/j.cub.2015.11.057},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-190870},
  pages     = {286-295},
  year      = {2016},
  abstract  = {Carnivorous plants, such as the Venus flytrap (Dionaea muscipula), depend on an animal diet when grown in nutrient-poor soils. When an insect visits the trap and tilts the mechanosensors on the inner surface, action potentials (APs) are fired. After a moving object elicits two APs, the trap snaps shut, encaging the victim. Panicking preys repeatedly touch the trigger hairs over the subsequent hours, leading to a hermetically closed trap, which via the gland-based endocrine system is flooded by a prey-decomposing acidic enzyme cocktail. Here, we asked the question as to how many times trigger hairs have to be stimulated (e.g., now many APs are required) for the flytrap to recognize an encaged object as potential food, thus making it worthwhile activating the glands. By applying a series of trigger-hair stimulations, we found that the touch hormone jasmonic acid (JA) signaling pathway is activated after the second stimulus, while more than three APs are required to trigger an expression of genes encoding prey-degrading hydrolases, and that this expression is proportional to the number of mechanical stimulations. A decomposing animal contains a sodium load, and we have found that these sodium ions enter the capture organ via glands. We identified a flytrap sodium channel DmHKT1 as responsible for this sodium acquisition, with the number of transcripts expressed being dependent on the number of mechano-electric stimulations. Hence, the number of APs a victim triggers while trying to break out of the trap identifies the moving prey as a struggling Na\(^+\)-rich animal and nutrition for the plant.},
  language  = {en}
}