Species possess characteristics that are considered adapted to burning and these allow them to outcompete species and dominate in fire prone environments. It has therefore been proposed that fire might have played a critical role in the observed expansion of the grasslands, during the late Miocene. The aim of this study was (i) to investigate whether plant response to fire was a result of physiology or (ii) whether it was due to phylogenetic history. This was achieved by doing a pair-wise comparison between Panicoideae (and Panicoideae) and non-Panicoideae (Danthonioideae and Aristidoideae) species. Pre-fire characteristics, that would enhance fire frequency and assist with plant recovery after burning, were compared across phylogenies and photosynthetic type. Post fire plant recovery was then followed in a field and pot comparison which examined the re-growth of the leaf canopy area, leaf mass, above-ground biomass and the cost of this to the below-ground biomass. The pre-fire characteristics showed both a photosynthetic and phylogenetic response. It was found that the species showed a greater canopy death during winter and had a lower moisture content than the species. These characteristics would potentially contribute towards a larger fuel load in the species. However, the comparison of the dead standing biomass at the end of winter and the below-ground biomass, showed a phylogenetic response with the Panicoideae having a proportionally larger dead standing biomass and below-ground biomass than the non-Panicoideae. These results suggest that not only did the Panicoideae have a larger potential fuel load but that they also shunted carbon below-ground, enabling a fast recovery after being burned. The post-fire results were more strongly determined by phylogeny than by photosynthetic type. The Panicoideae recovered faster and more completely than the non-Panicoideae grasses, possibly contributing to their success and expansion under conditions of increased fire frequency. Although recovery of the and Panicoideae were similar, frequently burnt grasslands are dominated by the Panicoideae. Hence, this dominance cannot be explained by differences in their fire responses and may be determined by the post-fire environmental conditions that potentially advantage species possessing the photosynthetic pathway. Panicoideae dominance is limited to mesic environments where fire is the likely driver of grassland expansion while more arid environments are dominated by non-Panicoideae species. Representative species from these non-Panicoid subfamilies showed poor recovery after fire. This suggests that factors other than fire were the likely drivers of these xeric grassland expansions. The ability of these subfamilies, and particularly the species, to cope with drought remains a likely selective mechanism that requires further research.

Made available in DSpace on 2014-08-20T13:25:43Z (GMT). No. of bitstreams: 1 Tese_Clauber_Mateus_Priebe_Bervald.pdf: 1713348 bytes, checksum: c9ae92634bc72e4a44156ded5d351214 (MD5) Previous issue date: 2009-08-09 / The use of sequences of DNA has been the base of comparative genomics for evolutionary studies. The transfer of information from model species to agricultural species has been revolutionizing the molecular genetics and strategies of crop improvement. The combination of classic methods of genetics and breeding with molecular technologies of genomic analysis opens a new perspective for the increase of the understanding of the genetic basis and the acceleration of breeding programs. Bioinformatics is becoming a tool that will be an essential part of the plant scientific research contributing to this challenge, and allowing inferences of function, structure and evolution of genes and genomes, search of markers, primers design, among other possibilities. In this sense, three studies of comparative genomics in grasses were accomplished, using bioinformatics tools. In the first work, the objective was to analyze the microsatellite abundance in genome fractions of 13 species of the genus Oryza, describing the rates, frequencies and pattern of distribution of the different microsatellites. The microsatellite frequency varies inversely proportional to the size of the genome of the specie of the genus Oryza. The A genome species presented the highest occurrences and frequencies for all types and total microsatellites. The trimers composed by cytosines and guanines presented the percentile largest of occurrence among the species, without direct relationship with the GC content of the species. In the second work, the promoter region of 1,000 bases pairs of the genes OsNramp of Oryza sativa subsp japonica cv. Nipponbare was investigated as for the abundance of cis-acting elements. The sequences were analyzed using the software Signal Scan Search of the website Plant Cis-acting Regulatory DNA Elements (PLACE) to the identification of different cis-acting elements present in each one of the promoter regions. Were detected 170 different cis-acting elements in the upstream region of the genes members of the family OsNramp subsp japonica cv. Nipponbare. A total of 14 elements were common to the eight members of the family OsNramp subsp japonica cv. Nipponbare. The element CACTFTPPCA1 was the most frequent motif in the promoter region of the genes of the family OsNramp of Oryza sativa subsp japonica cv. Nipponbare. The objective of the last work was to compare the sequences of oats with the species Arabidopsis, barley, rice, sugarcane, Sorghum, wheat and corn, looking for to infer evolutionary relationships of those species with the oats. Sequences of eight species of plants evaluable at the present moment, in the Unigene data bank in the National Center for Biotechnology Information - NCBI were downloaded and comparisons with oat made using the BLASTn and tBLASTx tools. It was observed that the bank of ESTs of oats UNIGENE-NCBI consists from many sequences a little similar to other species compared to nucleotides (46,72%) and aminoacids (74,97%). Only 4,56% of the sequences present in the UNIGENE-NCBI oat EST bank presents high similarity with sequences of mono and dicotyledonous species. / O uso de seqüências de DNA tem sido à base da genômica comparativa para estudos evolucionários e a transferência de informações de espécies modelo para espécies agrícolas tem revolucionado a genética molecular e estratégias de melhoramento das culturas. A combinação de métodos clássicos de genética e melhoramento com tecnologias moleculares de análise genômica abre uma nova perspectiva para a ampliação do conhecimento das bases genéticas e aceleração de programas de melhoramento. A bioinformática está se tornando em uma ferramenta que será parte essencial na pesquisa científica de plantas e que poderá contribuir muito para este desafio, permitindo fazer inferências de função, estrutura e evolução de genes e genomas, busca de marcadores, desenho de primers, entre outras possibilidades. Neste sentido, três estudos de genômica comparativa em gramíneas foram realizados, utilizando a bioinformática como ferramenta. No primeiro trabalho, o objetivo do trabalho foi analisar a abundância de microssatélites no genoma de 13 espécies do gênero Oryza obtidas do GeneBank do National Center for Biotechnology Information NCBI, com programa SSRLocator, descrevendo as taxas, freqüências e padrão de distribuição dos diferentes microssatélites. A freqüência de microssatélites varia inversamente proporcional ao tamanho do genoma da espécie no gênero Oryza. As espécies de genoma A apresentam as maiores freqüências para todos os tipos de microssatélites e totais no gênero Oryza. Os trímeros compostos por citosinas e guaninas apresentam o maior percentual de ocorrência entre as espécies de gênero Oryza, sem relação direta com o conteúdo GC da espécie. No segundo trabalho, a região promotora de 1000 pares de bases dos genes OsNramp de Oryza sativa subsp japonica cv. Nipponbare foi investigada quanto à abundância de elementos cis-acting. As seqüências foram analisadas utilizando o programa Signal Scan Search do portal Plant Cis-acting Regulatory DNA Elements (PLACE) para a identificação dos diferentes elementos cis-acting presentes em cada uma das regiões promotoras. Foram detectados 170 diferentes elementos cis-acting na região promotora dos genes membros da família OsNramp, sendo um total de 14 elementos comuns a região promotora dos oito membros da família gênica OsNramp de Oryza sativa subsp. japonica. O elemento CACTFTPPCA1 foi o motivo mais freqüente na região promotora dos genes membros da família OsNramp de Oryza sativa subsp. japonica. O objetivo do último trabalho foi comparar as seqüências de ESTs de aveia com as espécies Arabidopsis, cevada, arroz, cana-de-açúcar, sorgo, trigo e milho, buscando inferir relações evolutivas dessas espécies com a aveia. Seqüências de oito espécies de plantas disponíveis atualmente, no banco de dados Unigene no National Center for Biotechnology Information - NCBI foram baixadas e as comparações com a aveia foram feitas utilizando as ferramentas de BLASTn e tBLASTx. Observou-se que o banco de ESTs de aveia UNIGENE-NCBI consiste de muitas seqüências pouco similares a outras espécies comparados a nucleotídeos (46,72%) e aminoácidos (74,97%). Uma minoria de 4,56% das seqüências presentes no banco de ESTs de aveia UNIGENE-NCBI apresentam alta similaridade com seqüências de espécies de mono e dicotiledôneas.