RESUMO
Reed canary grass (RCG) is a perennial grass traditionally cultivated for forage. It is also used as fuel to produce energy in Finland and Sweden, and other countries have expressed interest in the cultivation of RCG. In China, arable land is limited. Salinity is considered to be a major factor limiting plant crop development and productivity. To boost biofuel production of RCG and extend its range in saline soil, we seek to improve its salt tolerance. Proline acts as an osmolyte that accumulates when plants are subjected to abiotic stress. P5CS plays a crucial role in proline biosynthesis. We isolated a P5CS gene from RCG, designated B231P5CS (GenBank accession No. JQ622685). B231P5CS is a fragment (971 bp) that encodes a 323-amino acid polypeptide. We also cloned an actin gene fragment from RCG as a reference gene in expression analysis of B231P5CS gene. Expression analysis revealed that B231P5CS transcripts were upregulated in leaves after treatment with salt (200 mM NaCl) and that transcript levels of B231P5CS reached a maximum 12 h after exposure, which was 14.69 times the level in control plants. The trends of expression were exactly opposite in roots; transcripts were downregulated after salt treatment. Proline concentration increased in leaves after stress. In contrast, proline content of roots decreased up to 3.6-fold relative to controls. Changes in proline concentration after stress were correlated with B231P5CS expression. Our results suggest that B231P5CS is a stress-inducible gene and plays a non-redundant role in plant development. This gene may be used to improve stress tolerance of RGC and other bioenergy feedstock.
Assuntos
Glutamato-5-Semialdeído Desidrogenase/genética , Complexos Multienzimáticos/genética , Phalaris/genética , Fosfotransferases (Aceptor do Grupo Álcool)/genética , Proteínas de Plantas/genética , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , DNA Complementar/química , DNA Complementar/genética , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Glutamato-5-Semialdeído Desidrogenase/classificação , Glutamato-5-Semialdeído Desidrogenase/metabolismo , Dados de Sequência Molecular , Complexos Multienzimáticos/classificação , Complexos Multienzimáticos/metabolismo , Phalaris/enzimologia , Phalaris/metabolismo , Fosfotransferases (Aceptor do Grupo Álcool)/classificação , Fosfotransferases (Aceptor do Grupo Álcool)/metabolismo , Filogenia , Folhas de Planta/genética , Folhas de Planta/metabolismo , Proteínas de Plantas/classificação , Proteínas de Plantas/metabolismo , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , Prolina/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Tolerância ao Sal/genética , Análise de Sequência de DNA , Cloreto de Sódio/farmacologia , Estresse Fisiológico/genética , Fatores de TempoRESUMO
Understanding the architecture of physiological functions from annotated genome sequences is a major task for postgenomic biology. From the annotated genome sequence of the microbe Escherichia coli, we propose a general quantitative definition of enzyme importance in a metabolic network. Using a graph analysis of its metabolism, we relate the extent of the topological damage generated in the metabolic network by the deletion of an enzyme to the experimentally determined viability of the organism in the absence of that enzyme. We show that the network is robust and that the extent of the damage relates to enzyme importance. We predict that a large fraction (91%) of enzymes causes little damage when removed, while a small group (9%) can cause serious damage. Experimental results confirm that this group contains the majority of essential enzymes. The results may reveal a universal property of metabolic networks.
Assuntos
Enzimas/química , Enzimas/metabolismo , Escherichia coli/enzimologia , Metabolismo/fisiologia , Modelos Biológicos , Complexos Multienzimáticos/química , Complexos Multienzimáticos/metabolismo , Simulação por Computador , Ativação Enzimática , Estabilidade Enzimática , Enzimas/classificação , Enzimas/deficiência , Complexos Multienzimáticos/classificação , Complexos Multienzimáticos/deficiência , Mutação , Relação Estrutura-AtividadeRESUMO
Nothing is known regarding the expression or function of the type IV Aeromonas pilus (Tap), which was recently identified following the cloning of a pilus biogenesis gene cluster (tapABCD). As a first step to determine the possible significance of Tap for Aeromonas virulence, the distribution of the tapA and tapD genes in hybridization group reference strains and clinical (n=42) and environmental (n=29) isolates was determined. Homologues of tapA and tapD were present in all strains tested. Hybridization with the tapA probe enabled us to differentiate between clinical and environmental isolates of A. veronii biovar sobria.