Temperature and photoperiod affect stress resistance traits in Drosophila melanogaster

The long‐term survival of species and populations depends on their ability to adjust phenotypic values to environmental conditions. In particular, the capability of dealing with environmental stress to buffer detrimental effects on fitness is considered to be of pivotal importance. Resistance traits are readily modulated by a wide range of environmental factors. In the present study, Drosophila melanogaster Meigen is used to investigate plastic responses to temperature and photoperiod in stress resistance traits. The results reveal that stress resistance traits (cold, heat, starvation and desiccation resistance) are affected by the factors temperature and sex predominantly. Cooler temperatures compared with warmer temperatures increase cold tolerance, desiccation and starvation resistance, whereas they reduce heat tolerance. Except for heat resistance, females are more stress‐resistant than males. Stress resistance traits are also affected by photoperiod. Shorter photoperiods decrease cold tolerance, whereas longer photoperiods enhance desiccation resistance. Overall, thermal effects are pervasive throughout all measured resistance traits, whereas photoperiodic effects are of limited importance in the directly developing (i.e. nondiapausing) flies used here, suggesting that pronounced photoperiodic effects on stress resistance traits may be largely limited to, and triggered by, diapause‐inducing effects.     

Synergistic temperature and ethanol effect on<Emphasis Type="Italic"> Saccharomyces cerevisiae</Emphasis> dynamic behaviour in ethanol bio-fuel production

The impact of ethanol and temperature on the dynamic behaviour of Saccharomyces cerevisiae in ethanol biofuel production was studied using an isothermal fed-batch process at five different temperatures. Fermentation parameters and kinetics were quantified. The best performances were found at 30 and 33°C around 120 g l^-1 ethanol produced in 30 h with a slight benefit for growth at 30°C and for ethanol production at 33°C. Glycerol formation, enhanced with increasing temperatures, was coupled with growth for all fermentations; whereas, a decoupling phenomenon occurred at 36 and 39°C pointing out a possible role of glycerol in yeast thermal protection.     

Cloning and Characterisation of Two H+ Translocating Organic Pyrophos-phatase Genes in Salix and Their Expression Differences in Two Willow Varieties with Different Salt Tolerances

Willows are one of the most important tree species for landscaping, biofuel and raw timber. Screening salt-tolerant willow varieties is an effective approach to balance wood supply and demand. However, more salt-tolerant willow varieties are required and little is known regarding the mechanism of salt tolerance at the gene expression level. In this paper, two willow varieties were studies in terms of their differences in salt-tolerances and mechanism of salt tolerance at the level of VP1 gene expression. The results showed that Salix L0911 (L0911) had higher biomass than Salix matsudana (SM), and salt injuries were less severe in L0911 than in SM. The activities of peroxidase and superoxide dismutase, as well as the contents of soluble protein and proline, were higher in L0911 than in SM, whereas the contents of Na⁺ and K⁺, as well as the Na⁺/K⁺ ratio, were lower in L0911 than in SM. Two VP1 genes (VP1.1 and VP1.2) cloned in L0911 and SM had similar sequences and structures. VP1.1 and VP1.2 belonged to different subgroups. Total expression levels of the VP1.1 gene in both roots and leaves of L0911 were higher than that in SM under normal conditions. Under salt stress, expression of VP1 in SM roots initially increased and then decreased, whereas the expression of VP1 in leaves of L0911 and SM, as well as in roots of L0911, decreased with increasing salt concentrations. This study increased our understanding of the salt-tolerance mechanism of willow and may facilitate the selection of salt-tolerant willow resources.     

Occurrence of mono- or disaccharides and polysaccharide reserves in mature pollen grains

 Pollen from 13 species of gymnosperms and angiosperms was studied for soluble and insoluble carbohydrates at dispersal. Starch reserves stored during pollen development give rise to carbohydrates at maturity. Combinations of different types of carbohydrates in mature pollen may depend on the extent of starch hydrolysis. An inverse relationship was found between the extent of starch hydrolysis and sucrose content. If the starch was scarcely de-polymerized, the cytoplasm had very low levels of soluble sugars and none of the periodic acid-Schiff (PAS)-positive material as found in pollen not subject to high dehydration (Cucurbita pepo L., Zea mays L.). After total or partial starch hydrolysis, insoluble PAS-positive oligo/polysaccharides were found in the cytoplasm associated with much soluble sugar, and the pollen grains were dehydrated at dispersal as in Typha latifolia L., Chamaerops humilis L., Trachycarpus excelsa Wendl., and other specimens. Intermediate levels of starch and soluble sugars, together with cytoplasmic PAS-positive material, characterized species with dehydrated pollen such as Pinus halepensis Miller. Carbohydrates may be related to pollen longevity, which largely depends on the abundance of sucrose, which is known to protect membrane integrity. The relationship between PAS-positive material and pollen viability is unclear at present. Received: 30 July 1996 / Revision accepted: 18 December 1996     

Phytochrome and UV signal transduction pathways

The phytochromes are the best studied plant photoreceptors, controlling a wide variety of responses at both whole plant and single cell levels. Three signal transduction pathways, dependent on cGMP and/or calcium, have been found to be utilized by phytochrome to control the expression of genes required for chloroplast development (e.g., CAB and FNR) and anthocyanin biosynthesis (e.g., CHS). In particular, cGMP is a second messenger positively regulating CHS gene expression whilst calcium and calmodulin act as negative regulators. In addition to phytochrome regulation of CHS we have begun to examine the signal transduction pathways utilized by UV photoreceptors. In contrast to phytochrome-mediated responses, results indicate a role for calcium and calmodulin as positive regulators of CHS gene expression in UV light.     

The manipulation of polar head group composition of phospholipids in the wheat Miranovskaja 808 affects frost tolerance

Caryopses of the frost-resistant cultivar of the wheat Triticum aestivum L., Miranovskaja 808, were germinated and grown in the presence of various concentrations of choline chloride. Changes in the composition of leaf total phospholipids and leaf total fatty acids at two extreme temperatures (25°C and 2°C) as well as changes in frost resistance were followed. A choline chloride concentration-dependent accumulation of phosphatidyl choline was observed in the leaves. Seedlings grown at 2°C accumulated more phosphatidyl choline at each choline chloride concentration than those grown at 25°C. There was an inverse relationship between the contents of phosphatidyl choline and phosphatidic acid in the leaves. Neither the temperature nor choline chloride seemed to affect fatty-acid composition. Modification of polar-head group composition of phospholipids affected frost tolerance: Seedlings grown in the presence of 15 mM choline chloride at 25°C exhibited a freezing resistance equal to that of hardened controls. The data indicate that the polar-head group composition of membrane phospholipids in plants can be easily manipulated and point to the importance of phosphatidyl choline in cold adaptation processes.     

Resistance to photoinhibition of photosystem II and catalase and antioxidative protection in high mountain plants

In leaves of three alpine high mountain plants, Homogyne alpina, Ranunculus glacialis and Soldanella alpina, both photosystem II (PSII) and the enzyme catalase appeared to he highly resistant to photoinactivation under natural field conditions. While the Dl protein of PSII and catalase have a rapid turnover in light and require continuous new protein synthesis in non-adapted plants, little apparent photoinactivation of PSII or catalase was induced in the alpine plants by translation inhibitors or at low temperature, suggesting that turnover of the Dl protein and catalase was slow in these leaves. In vitro PSII was rapidly inactivated in light in isolated thylakoids from H. alpina and R. glacialis. In isolated intact chloroplasts from R. glacialis, photoinactivation of PSII was slower than in thylakoids. Partially purified catalase from R. glacialis and S. alpina was as sensitive to photoinactivation in vitro as catalases from other sources. Catalase from H. alpina had, however, a 10-fold higher stability in light. The levels of xanthophyll cycle carotenoids, of the antioxidants ascorbate and glulathione, and of the activities of catalase, superoxide dismutase and glutathione reductase were very high in S. alpina, intermediate in H. alpina, but very low in R. glacialis. However, isolated chloroplasts from all three alpine species contained much higher concentrations of ascorbate and glutathione than chloroplasts from lowland plants.