Full text
| |
| Author(s): |
Gustavo Turqueto Duarte
Total Authors: 1
|
| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia |
| Defense date: | 2012-08-29 |
| Examining board members: |
Michel Georges Albert Vincentz;
Anete Pereira de Souza;
Camila Caldana;
Jörg Kobarg;
Fabio Tebaldi Silveira Nogueira
|
| Advisor: | Michel Georges Albert Vincentz |
| Abstract | |
Plants, as sessile organisms, have developed a set of mechanisms that allow efficient adaptation to adverse environmental conditions. These processes rely on the integration of hormone biosynthesis, activation of stress-responsive pathways and on a balanced use of the available energy. Sugars, besides their role as carbon and energy sources, may also function as signaling molecules that may act together with hormonal signals to trigger adaptive responses to biotic and abiotic stresses. In this context, several studies have indicated an important relation between abscisic acid (ABA), one of the major hormones related to abiotic stresses responses, and glucose. ABA signaling, besides its function over transcription control, is known to involve factors regulating the stability of mRNAs. However, the importance of glucose-mediated mRNA decay control is essentially unknown. Our work intended to evaluate the potential of the participation of post-transcriptional regulations in response to ABA and glucose in Arabidopsis thaliana, by determining mRNA profile alteration in response to these signals after transcription inhibition. An experimental model which optimizes the conditions for transcription inhibition was established and used for transcriptome profiling with CATMA microarrays. A total of 962 genes were found to be differentially expressed after the treatments, suggesting a possible post-transcriptional control acting upon 204, 245 and 513 transcripts in response to glucose, ABA and the combination glucose + ABA, respectively. The genes were classified by their functions according to Gene Ontology, suggesting a close relation with adaptive response to stress conditions. Apparently, ABA- and glucose-mediated control of mRNA stability follows two opposite strategies, while ABA post-transcriptional responses may also act as a fast negative feedback mechanism over its own core signaling pathway, as a way to desensitize and reset the pathway responses. The second part of this work focused on the participation of microRNAs (miRNAs) pathway in responses mediated by glucose during plant early developmental stages. The mutants ago1-25 and hyl1-2, which are deficient in miRNA activity and biogenesis, respectively, showed hyposensitivity to glucose during a narrow time window of early plant development, between germination and seedling establishment. Such result raises the possibility that miRNA pathway may be involved in the glucose-mediated delay of early seedling development. To obtain further evidences about which miRNAs could be involved, the expression profile of 200 pri-miRs was evaluated by large-scale quantitative real-timepolymerase chain reaction (qRT-PCR) profiling, indicating that 38 pri-miRNA are potentially regulated by glucose, several of which are known to participate directly or indirectly in plant development. The data indicate that deficiency in miRNA machinery leads to an imbalance on glucose control over gene expression during early seedling development (AU) | |