5. Discussion
5.9 Model of the proposed contribution of B-GATAs in greening of Arabidopsis
The major question and the core of the research conducted in this thesis was how the B-GATA GNC and GNL can promote greening in Arabidopsis. It can be concluded that GNC and GNL are able to control greening not only in a just linear way, such as by regulate genes related to chlorophyll biosynthesis pathway.
Instead, they do so by being able to coordinate, synchronize and promote the expression of genes, which can induce greening in many different ways (Figure 42). Such complex regulation of greening is in line with the importance of chlorophyll production for the survival of the plants that do not solely rely on the upregulation of a single pathway. Moreover, the results, which are presented in this thesis, could shape a model that can be used, either partially or as a whole, to expand our knowledge in regulation of the chlorophyll biosynthesis also in other photosynthetic organisms. This can be a subject of future research, and could shed more light on the evolutionary conservation of the regulation of the chlorophyll biosynthesis mechanism.
Different colored letters represent proteins with an implication in different pathways which contribute to greening in Arabidopsis. The light-blue letters refer to the transcription factors with a positive role in greening. The purple letters refer to proteins, which regulate transcription in the chloroplast. The green letters refer to enzymes, which catalyze steps in the chlorophyll biosynthesis pathway. The red letters refer to GUN2, an enzyme which play a role in the heme/phytochromes pathway. The brown letters refer to PIF transcription factors, which play a role in greening. ( ): indicates induction of gene expression and ( ) : indicates repression of gene expression.
94
Figure 42: Proposed model of the mechanism through which GNC and GNL contribute to greening in Arabidopsis.
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104 Appendix
Table 9: List of genes related to tetrapyrrole pathway, regulators of chlorophyll biosynthesis, chloroplast division, photosynthesis, import-export chloroplast machinery and carotenoids biosynthesis, presented in microarrays, RNA-seqs and ChIP-seq.
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Table 9: continue
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Table 9: continue
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Table 10: List of genes from the overlap of ChIP-seq with pGNL:GNL:HA gnc gnl and the RNA-seq with 35S:GNC:YFP:HA:GR gnc gnl for 3 h Dex and CHX (filtered with fold change threshold/F.C. 2.45 and FDR < 0.01).
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Table 11: List of genes from the overlap of ChIP-seq with pGNL:GNL:HA gnc gnl and the RNA-seq with 35S:GNL:YFP:HA:GR gnc gnl for 3 h Dex and CHX (filtered with fold change threshold/F.C. 1.2 and FDR < 0.1).
Table 12: List of genes from the overlap between the common genes from the ChIP-seq with pGNL:GNL:HA gnc gnl and the RNA-seq with 35S:GNC:YFP:HA gnc gnl with a list of genes with a role in chlorophyll biosynthesis.
Table 13: List of genes with overlap between the common genes from the ChIP-seq with pGNL:GNL:HA gnc gnl and the RNA-seq with 35S:GNL:YFP:HA gnc gnl with a list of genes with a role in chlorophyll biosynthesis.