Biochemical analysis of trehalose and its metabolizing enzymes in wheat under abiotic stress conditions

In this study, three wheat cultivars (Triticum aestivum L.) Tosun, Bolal (stress tolerant) and Cakmak (stress sensitive) were analysed for the presence of trehalose. Using gas chromatography-mass spectrometry (GC-MS) analysis, trehalose was unambiguously identified in extracts from seeds and seedlings of different wheat cultivars. The trehalose amount was quantified by high performance liquid chromatography (HPLC) connected with refractive index detector. Effects of drought and salt stress on trehalose contents of wheat cultivars were studied at seedling level and trehalose analysis was achieved both on shoot and root tissues. It was found that trehalose had accumulated under salt and drought stress conditions in all wheat cultivars. Furthermore, trehalose metabolizing enzymes; trehalose-6-phosphate synthase (TPS) and trehalase enzyme activities were measured in roots and shoots of wheat cultivars under control, salt and drought stress conditions. TPS activity sharply increased under stress conditions and the activity of TPS in roots under drought stress condition was the highest and reached to three to four times of its activity under control condition. The increase in the activity of TPS showed parallelism with trehalose accumulation under stress condition. Trehalase activity in Bolal cultivar decreased under both salt and drought stress conditions, however there was no significant change in trehalase activity of Cakmak variety. To the best of our knowledge, this is the first report on trehalose metabolizing enzymes under stress conditions. (c) 2005 Elsevier Ireland Ltd. All rights reserved

Photoelectrochemical H-2 production by using bacteriorhodopsin immobilized in PAG

Bacteriorhodopsin (BR), a protein found in the purple membrane of Halobacterium halobium is used as a biocatalyst in photoelectrochemical hydrogen production in a NaCl solution. In present study the biocatalytic effect of BR of a new strain MILTU and strain S-9 were investigated in immobilized membranes The photoelectrochemical hydrogen production experiments were performed in a batch type glass reactor with free H. halobium packed cells or H halobium cells immobilized in polyacrylamide gel (PAG). It was found that the presence of BR in the reactor enhances the hydrogen production rate upon illumination. Immobilization increased the amount of hydrogen produced per mole of BR. The maximum moles of hydrogen produced per mote of BR used was obtained by H. halobium MILTU packed cells immobilized in PAG. The presence of BR regulates the pH of the system, increases the hydrogen production rate and causes light-induced proton dissociation, which lowers the electrical power requirement for the electrochemical conversion

Indicadores fisiológicos da interação entre deficit hídrico e acidez do solo em cana-de-açúcar Physiological indicators of the interaction between water deficit and soil acidity in sugarcane

O objetivo deste trabalho foi avaliar os indicadores fisiológicos da interação entre deficit hídrico e acidez do solo em plantas jovens de cana-de-açúcar. As plantas foram submetidas a três tratamentos de disponibilidade hídrica, medidos em percentagem de capacidade de campo (CC) - sem estresse (70% CC), estresse moderado (55% CC) e estresse severo (40% CC); e três tratamentos de acidez no solo, medidos em termos de saturação por bases (V) - baixa acidez (V = 55%), média acidez (V = 33%) e alta acidez (V = 23%). O experimento foi realizado em casa de vegetação a 29,7±4,3ºC e 75±10% UR. O delineamento experimental utilizado foi o de blocos ao acaso, em esquema fatorial 3x3, com quatro repetições. Após 60 dias, foram determinados os teores de solutos compatíveis - trealose, glicina betaína e prolina - na folha diagnóstico e o crescimento inicial da parte aérea. Os solutos compatíveis trealose, glicina betaína e prolina são indicadores do efeito da interação dos estresses hídrico e ácido no solo. O acúmulo dos solutos compatíveis nos tecidos foliares das plantas não é capaz de impedir a redução na produção de matéria seca da cana-de-açúcar, resultante do agravamento nas condições de disponibilidade hídrica e de acidez no solo.<br>The aim of this work was to assess the physiological indicators of the interaction between water deficit and soil acidity, in sugarcane. The plants were submitted to three treatments of water availability - no stress (70% of field capacity, FC), moderate stress (55% FC), and extreme stress (40% FC); and three acidity treatments - no acidity [base saturation (V) = 55%], average acidity (V = 33%), and high acidity (V = 23%). The experiment was carried out in greenhouse, with 29.7±4.3ºC and 75±10% RH. The experimental design was in randomized blocks, in 3x3 factorial arrangement, with four replicates. After 60 days, the contents of compatible solutes - trehalose, glycine betaine and proline - in the diagnostic leaf and the initial growth of shoots were determined. The compatible solutes trehalose, glycine betaine, and proline are indicators of the interaction of water and acidity stresses in the soil. The accumulation of compatible solutes in plant foliar tissues can not prevent sugarcane losses in dry matter production, caused by increasing water deficit and soil acidity

Trocas gasosas e balanço de carboidratos em plantas de cana-de-açúcar sob condições de estresses radiculares

Embora a resposta da fotossíntese de plantas de cana-de-açúcar a estresses ambientais seja conhecida, o acúmulo de fitomassa e a dinâmica de carboidratos de reserva diante da exposição simultânea ao frio e à seca são pouco conhecidos. Este trabalho objetiva investigar o efeito do déficit hídrico e da baixa temperatura radicular, isolados e simultaneamente, no genótipo de cana-de-açúcar IACSP94-2094, considerado tolerante à seca. Como hipótese, consideramos que este genótipo também é tolerante à baixa temperatura radicular, já que baixas temperaturas e déficit hídrico ocorrem simultaneamente no campo. A imposição da restrição hídrica de forma isolada ou simultaneamente à baixa temperatura radicular causou redução do potencial da água na folha e da assimilação de CO2, o que não foi observado nas plantas submetidas apenas à baixa temperatura do substrato. Os teores foliares de carboidratos não estruturais, de sacarose e de amido aumentaram nas plantas sob frio radicular. Nos tratamentos com déficit hídrico, apenas o teor de amido foliar diminuiu. Os estresses radiculares causaram aumento nos teores de açúcares solúveis totais e diminuição no teor de amido nas raízes. Como o acúmulo de fitomassa das plantas não foi afetado, mesmo com a restrição no crescimento radicular nos tratamentos com baixa temperatura do substrato, conclui-se que o genótipo de cana-de-açúcar IACSP94-2094 contém indícios de tolerância à baixa temperatura radicular. A manutenção do crescimento da planta deve estar associada à degradação das reservas de amido foliares e radiculares