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| Author(s): |
Letícia Bianca Pereira
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia |
| Defense date: | 2018-08-20 |
| Examining board members: |
Laura Maria Mariscal Ottoboni;
Fabiana Fantinatti Garboggini;
Suzan Pantaroto de Vasconcellos;
Edmilson Ricardo Gonçalves;
Marcelo Falsarella Carazzolle
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| Advisor: | Laura Maria Mariscal Ottoboni |
| Abstract | |
Sugarcane is a very important crop for the Brazilian economy, especially for the State of São Paulo, where the largest production of this crop is concentrated. However, the emission of carbon dioxide in the atmosphere is promoting an increase in the average temperature and a decrease in the rainfall in the sugarcane producing regions. In the rhizosphere, soil bacteria are closely related to plants and they can promote plant growth. Thus, the study of the effect of environmental changes on sugarcane rhizosphere could provide new informations about plant-microbiota interaction and how the microorganisms could help plants to survive in adverse conditions. Therefore, the aim of the present work was to evaluate the effect of water stress on the associated-rhizosphere microbiota of two sugarcane varieties (CTC9001 and RB855536) by metatranscriptome sequencing. In addition, the cultivable rhizosphere microbiota of CTC9001 variety was isolated and evaluated for the ability to promote plant growth. Chapter 1 of this work presented the results of rhizosphere metatranscriptome of the dry-resistant sugarcane variety (CTC9001). The results indicated that Proteobacteria, Actinobacteria and Bacteroidetes dominated the bacterial community associated with rhizosphere of the dry-resistant sugarcane variety and that water stress caused changes in these communities. A decrease in the expression of genes related to growth and energy metabolism occurred mainly in the samples submitted to eight days of water stress and were related to the Sorangium and Rhodanobacter genera. On the other hand, genes associated with functions such as flagella mobility, cell adhesion and protein degradation increased their expression in eight days of water stress and were related to the genus Aequorivita. This genus also showed a positive correlation with the organic acids exuded by the plant. The same water stress experiment was performed for the rhizosphere-associated microbiota of the dry-sensitive sugarcane RB855536. Thus, Chapter 2 presented the results obtained from the comparison between the rhizosphere-associated microbiota to the two sugarcane varieties (resistant x sensitive). These results showed that the microbiota of dry-sensitive sugarcane variety presented different responses compared to the data obtained for the resistant one. This difference in microbial response between the two sugarcane varieties was observed even in short times of water stress (two days). The dry-sensitive variety showed changes in the expression of genes associated with DNA and ribosome binding proteins, throughout the entire period of drought stress evaluated. In this variety, the genus Streptomyces and the family Polyangiaceae showed the highest values of gene expression at 12 days of water stress, probably due to the ability to form spores or respond faster to environmental changes. Streptomyces also presented several negatively correlated transcripts with organic acids exuded by the plant, which may have acted as signals for changes in the expression of some of its genes. Finally, the results of the isolation of bacteria from CTC9001 sugarcane rhizosphere were presented in Chapter 3. The analyzes revealed a high abundance of Arthrobacter, Pseudomonas, Microbacterium and Bacillus genera. Many isolates showed positive results for plant growth capacity and growth under water stress (in the presence of PEG), suggesting that the isolates could be used as components of commercial biofertilizers for agriculture. Plant growth tests on tomato plants revealed that the isolate Pseudomonas sp. WS02-30 increased the root length of plants, probably due to its ability to produce indole acetic acid (IAA) and 1-aminocyclopropane-1-carboxylate (ACC) deaminase (AU) | |
| FAPESP's process: | 14/05929-0 - Impact of elevated concentration of CO2 and water stress in the microbiota associated with sugarcane rhizosphere |
| Grantee: | Letícia Bianca Pereira |
| Support Opportunities: | Scholarships in Brazil - Doctorate |