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Characterization of subunit A of the Eukaryotic translation initiation factor 3 in Arabidopsis thaliana
Raabe, Karel ; Michailidis, Christos (advisor) ; Retzer, Katarzyna (referee)
In plants, translation regulation plays an important role during progamic phase, fertilization and seed development. The process of translation is mostly regulated in its initiation phase, where Eukaryotic translation initiation factor 3 (eIF3) is the largest and most complex initiation factor, consisting of 12 different subunits. In plants, single eIF3 subunit mutants caused various growth and development defects, depending on the particular subunit that was mutated. However, not all the plant eIF3 subunits were characterized to this date. The objective of this work was to functionally characterize the eIF3 subunit A using Arabidopsis thaliana as the main model plant. We described in this work that plant eIF3A proteins share high levels of homology and domain organization with eIF3A subunits from non-plant eukaryotic species but contain regions specific only to plants. Next we described that Arabidopsis thaliana AteIF3A gene is transcribed in highly proliferating tissues, its protein product localizes to cytoplasm and around pollen vegetative cell nucleus and observed an increased frequency of defective pollen grains and defects in seed formation in plants with T-DNA insertion localized to the AteIF3A gene. We also produced stable transgenic Nicotiana tabacum lines expressing heterologous AteIF3A...
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Characterization of eukaryotic translation initiation factor 3 subunits (eIF3) in A. thaliana male gametophyte
Linhart, Filip ; Hafidh, Said (advisor) ; Retzer, Katarzyna (referee)
From RNA-to-protein, translation initiation and protein synthesis is mediated by trans-acting factors that recognize mRNA features common to almost all eukaryotes. Eukaryotic translation initiation factor 3 complex (eIF3) is a highly conserved protein complex that recognizes 5'-CAP elements of the mRNA to initiate translation. eIF3 consists of nine subunits, three of them having two isoforms: eIF3A, eIF2B1, eIF3B2, eIF3C1, eIF3C2, eIF3D, eIF3E, eIF3F, eIF3G1, eIF3G2, eIF3H and eIF3K. This work deals with functional characterization, expression and subcellular localization of eIF3B1, eIF3B2 and eIF3E in Arabidopsis thaliana male gametophyte and interaction of eIF3E with the Constitutive photomorphogenesis 9 (COP9) complex as a regulatory complex of eIF3E post-translational control. Here we show that depletion of eif3b1 or eif3b2 is not gametophytic lethal and that the two protein might function redundantly, whereas, knockout of eIF3E causes male gametophyte lethality. Interestingly, eif3b1 show post-fertilization defects during embryogenesis, suggesting that its redundancy with eIF3B2 is restricted to the gametophyte. Gene expression studies revealed high expression of eIF3 subunits in actively dividing zones of leaf primordia, root meristem and root elongation zones as well as in the vegetative...
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The role of small non-coding RNAs in the regulation of plant reproductive development
Hromadová, Michaela ; Honys, David (advisor) ; Rothová, Olga (referee)
Small RNAs (sRNA) are broadly defined as regulatory molecules of 21-24 nucleotides in length which belong to the class of noncoding RNAs. They usually originate in response to the presence of double-stranded RNA in the cells and facilitate transcriptional and posttranscriptional gene silencing of complementary sequences. Their role lies not only in defence against exogenous nucleic acids, but primarily in the regulation of endogenous genes. Typical target molecules of plant sRNA are transposable elements and genes encoding the transcription factors involved in the control of key developmental transitions like the initiation of the reproductive phase and the regulation of its progress. The aim of this thesis is a summary of functional roles of individual small RNA in plant reproductive development, with focus to the female and male gametophytes and in the protection against the transition of transposable elements to following generations. Both endogenous and exogenous sRNA are amply utilized in plants, because they provide an immediate and direct response of the organism to rapidly changing conditions, and thus undoubtedly belong to the key factors which contribute to their phenotypic plasticity.
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