Molecular characterization of salt-stress-associated protein in citrus: protein and cDNA sequence homology to mammalian glutathione peroxidases

A gene encoding for a citrus salt-stress-associated protein (Cit-SAP) was cloned from Citrus sinensis salt-treated cell suspension. The gene, designated csa, was isolated from a cDNA expression library. The partial amino acid sequence of the protein, as well as that deduced from the nucleotide sequence of csa, revealed a considerable homology to mammalian glutathione peroxidase (GP), and to clone 6P229 from tobacco protoplasts. The increased expression of Cit-SAP in NaCl-treated cultured citrus cells and in citrus plants irrigated with saline water, and its similarity to GP, raise the possibility that one of the effects of salt stress in plants may be the increase of the level of free radicals.     

Biomass structure and dry matter dynamics of subtropical alluvial and exotic Ligustrum forests at the Río de la Plata,Argentina

Biomass, litterfall, litter standing crop, and decomposition was studied in a native subtropical alluvial forest locally known as Selva Marginal (SM) and an exotic Ligustrum lucidum forest (LF) at the Reserva Integral de Punta Lara, Buenos Aires Province, 34°47S and 58°1W. The alluvial forest site was at the southern limit of distribution of subtropical forests in South America. The Ligustrum forest was invading disturbed areas. Total biomass was 147.7 Mg/ha (86% aboveground and 14% belowground) in the SM, and 71.4 Mg/ha (93% and 7%, respectively) in the LF. Litterfall was 10.3 Mg/ha·yr and 13.8 Mg/ha·yr respectively. Annual leaf decomposition rate was greater for Ligustrum (k=4.07) than for SM species (k=1.48). The mean residence time of aboveground biomass was 12 yr for the SM and 5 yr for the LF. The k₁ values (litterfall/standing crop) were 1.9 and 2.0 for SM and LF respectively. The influence of coastal road and wall in the hydroperiod, native forested wetland ecosystem survival and exotic forest invasion is discussed.     

Vertical structure of seed banks and the impact of depth of burial on recruitment in two temporary marshes

The structure of the seed bank (including Chara oospores), in relation to depth within the sediment and disturbance, was studied in two Rhône delta temporary marshes for two years. The seeds of all species were concentrated in the top 2 cm of sediment with very low numbers beeing found below 4 cm. When an exclosure eliminated disturbances of the sediment by animals, the vertical repartition of seeds at site 2 was more pronounced than outside the exclosure.In experiment 1, the emergence capacity of seeds from different depths and buried under layers of sterile equivalent to those in the field was measured. Depending of the species, 22 to 98% of the seeds germinated from unburied seeds in the top 2 cm. Only 1% of the oospores of Chara (from site 2) at 2 to 4 cm depth in the sediment emerged.In experiment 2, surface seed bank samples were placed under 0, 2 or 4 cm sterile sediment depth. The samples contained numerous recent seeds and the emergence percentage reached 41% (for Ruppia maritima). Only the seeds of Zannichellia spp failed to germinate from a depth of 2 cm or more. The emergence percentage from 2 cm depth or more was always lower than at the surface. These experiments showed that both burial and ageing of seeds decrease germination capacity.The majority of the active seeds located at the surface germinate when the marsh is flooded. Seeds located between 2 and 4 cm can be brought back to the surface by disturbances and play the role of a reserve involved in maintenance of populations that go without seed production for one or some years.     

Submerged vascular plants and water chemistry in the coastal marsh Albufera de Mallorca (Balearic Islands)

Ten species of aquatic macrophytes have been analyzed for seven environmental variables by means of a significance test. A synthetic view has been obtained through a cluster analysis for species and a principal component analysis for 17 variables which form the multidimensional space where we project the species habitats. Myriophyllum spicatum L., Najas marina L., Potamogeton crispus L., Potamogeton pectinatus L. and Zannichellia pedunculata Reichenb. are widely distributed in the Albufera. Ceratophyllum submersum L. and Ruppia maritima L. var. brevirostris Ag. are considered stenoic. The tolerance of Ceratophyllum submersum to salts is significantly low and that of Ruppia cirrhosa (Petagna) Grande and Ruppia maritima var. brevirostris significantly high. Ceratophyllum submersum has a significantly negative distribution with regard to chlorophyll a and phosphate concentrations. Ceratophyllum demersum L. and C. submersum primarily occur in nitrate-rich waters whereas Ruppia cirrhosa primarily occurs in low nitrate waters.     

The influence of sampling method on the classification of wetland macroinvertebrate communities

Macroinvertebrate communities sampled by a corer, plankton net and sweep net from five wetlands on the Swan Coastal Plain were compared. The composition of the fauna collected in sweeps and tows was generally similar and differed from that collected in the cores. Cores caught fewer species than tows and sweeps at all wetlands and did not capture fast swimming hemipterans or less abundant taxa. The highest species richness was recorded in sweep samples in four out of the five wetlands. Classification (TWIN-SPAN) and ordination (SSH) of the samples collected in sweeps and tows gave good separation of the wetlands, whereas classification of core samples did not. Coring appeared to be the least suitable sampling method for describing the major components of the macroinvertebrate communities of these wetlands. Plankton tows were useful if the time available for sorting was limited as these samples were free of sediments and generally gave similar results to those obtained with sweeps. Sweeps appeared to be the most useful method for a large classification study as they collected more species and resulted in the best discrimination amongst wetlands.     

Application of computer to monitoring and control of fermentation process: Microbial conversion of ML-236B Na to pravastatin

An automatic feeding process for microbial hydroxylation of ML236B sodium salt (ML-236B Na; compactin) by Streptomyces carbophilus SANK 62585 was developed. The hydroxylated product, pravastatin sodium salt (pravastatin; trade name Mevalotin), is an inhibitor of 3-hydroxy-3-methyglutaryl-coenzyme A reductase (HMG-CoA reductase) used as cholesterol-lowering drug. The hydroxylation activity of S. carbophilus was induced by the addition of ML236B Na to culture broth but inhibited by high concentration of ML236B Na. In order to obtain high conversion yield, it was necessary to maintain optimum ML236B Na concentration throughout the fermentation by continuous feeding. For this purpose, we developed an on-line monitoring method, which mainly consisted of a cross-flow filtration module, high-performance liquid chromatography (HPLC) analyzer, feed pump, and microcomputer for regulation of ML236B Na concentration. An algorithm for control of ML236B Na feed rate based on feedback and feed-forward control where conversion rate after Deltat was estimated by using regression analysis of the five latest values of conversion rate. In a fed-batch culture employing this system, the concentration of ML236B Na was maintained at optimum level during the fermentation and the productivity of pravastatin was increased threefold over that obtained in manual control culture. (c) 1993 John Wiley & Sons, Inc.     

Conservation of salt lakes

Salt lakes have a variety of important uses and values, including especially both economic and scientific ones. These uses and values have been and are increasingly subject to degradation from a variety of impacts: diversion of inflows, pollution, agricultural practices, and introduction of exotic species are among the more important. Recognition of these impacts upon salt lakes has led to some international and national measures for their conservation, but considerably more effort in this direction is needed. Against this background, Mono Lake, California, USA, and the Aral Sea, central Asia, are discussed as two localities which bring into sharp focus the various matters discussed in the paper. Finally, attention is drawn to the need to conserve the Akrotiri Salt Lake, Cyprus.     

嗜盐耐盐微生物抗盐胁迫相关离子转运蛋白研究进展

离子转运蛋白在维持细胞内pH稳态、离子动态平衡等方面发挥着重要作用。钠离子转运体和钾离子转运体在嗜盐耐盐微生物中广泛存在,其"保钾排钠"机制是微生物抗盐胁迫的两大策略之一。近年来,嗜盐耐盐微生物中许多新型钠、钾离子转运体被陆续发现,如RDD蛋白、UPF0118蛋白、DUF蛋白和KimA蛋白等;Fe³⁺、Mg²⁺等其他金属离子的转运蛋白也被证实可通过影响微生物胞内相容性溶质的合成起到渗透调节的作用。本文综述了嗜盐耐盐微生物中抗盐胁迫相关的各类离子转运蛋白,分析其分子结构和工作机理,并对这些蛋白在农业方面的应用进行了展望。继续发现新的离子转运蛋白,探究抗盐胁迫相关离子转运蛋白的结构和机理,解析各转运系统的协同作用及分子调控机制,将进一步加深对嗜盐耐盐微生物抗盐胁迫调控的认识,并为盐碱地农作物的改良等提供新的思路。     

Global mangrove root production,its controls and roles in the blue carbon budget of mangroves

Mangroves are among the most carbon-dense ecosystems worldwide. Most of the carbon in mangroves is found belowground, and root production might be an important control of carbon accumulation, but has been rarely quantified and understood at the global scale. Here, we determined the global mangrove root production rate and its controls using a systematic review and a recently formalised, spatially explicit mangrove typology framework based on geomorphological settings. We found that global mangrove root production averaged ~770 ± 202 g of dry biomass m⁻² year⁻¹ globally, which is much higher than previously reported and close to the root production of the most productive tropical forests. Geomorphological settings exerted marked control over root production together with air temperature and precipitation (r² ≈ 30%, p < .001). Our review shows that individual global changes (e.g. warming, eutrophication, drought) have antagonist effects on root production, but they have rarely been studied in combination. Based on this newly established root production rate, root-derived carbon might account for most of the total carbon buried in mangroves, and 19 Tg C lost in mangroves each year (e.g. as CO₂). Inclusion of root production measurements in understudied geomorphological settings (i.e. deltas), regions (Indonesia, South America and Africa) and soil depth (>40 cm), as well as the creation of a mangrove root trait database will push forward our understanding of the global mangrove carbon cycle for now and the future. Overall, this review presents a comprehensive analysis of root production in mangroves, and highlights the central role of root production in the global mangrove carbon budget.     

Microhabitat use by marsh-edge fishes in a Louisiana estuary

Synopsis We used a drop sampler to characterize use of the marsh-edge ecotone by small fishes along two transects running inland from the Gulf of Mexico for ca. 25 km in Louisiana's Barataria-Caminada Bay System. Monthly sampling was stratified among upper, middle, and lower reaches and within reaches to characterize fish responses to salinity, depth, distance from shore, substrate, dissolved oxygen concentration, temperature, turbidity, velocity, and emergent stem density. In 681 quantitative samples, covering 658 m², collected between October 1987 and October 1989, we collected 57 fish species and 16 864 individuals, primarily larvae and juveniles. The 15 most abundant fishes, comprising 97.7% of all individuals, were concentrated near the marsh edge (i.e., 0 to 1.25 m distance). Some significant differences within species for seasonal variables (e.g., temperature and dissolved oxygen concentration) reflected the ephemeral duration of early life history stages. Other differences reflected ontogenetic microhabitat shifts (e.g., depth and distance from shore). Within ecological groups, characterized as demersal residents, nektonic transients, and demersal transients, spatial and temporal segregation reflected the particular habitat requirements of each species. In a principal component analysis of microhabitat use, the first three components were interpreted as seasonal, depth-and-distance, and salinity axes, respectively. The array of species and size classes in principal component space reflected the complex dimensionality of microhabitat use. The high density of fish larvae and juveniles near the marsh edge confirmed the importance of the marsh-edge ecotone as a nursery for many estuarine-dependent fishes.