Effects of abiotic factors and biocontrol agents on chlamydospore formation in Fusarium graminearum and Fusarium sporotrichioides

Chlamydospores are vital asexual resting cells, which allow most of the Fusarium pathogenic strains to retain their longevity, thus ensuring survival of viable reproductive cells. This study suggested that both abiotic – extreme temperature and growth media, and biotic – antagonistic Bacillus amyloliquefaciens SMCD 518 and mycoparasititic Acremonium strictum SMCD 504 are natural stressors able to shift chlamydospores formation in Fusarium graminearum and F. sporotrichioides under in vitro conditions. In F. sporotrichioides, Minimal Conversion Media (MCM) with mannitol supplement induced high chlamydospore size, and chain abundance at optimal 21°C and extreme 37°C temperatures, respectively. F. graminearum showed low chlamydospore formation on MCM–mannitol, even when exposed to 37°C under prolonged 5 days incubation. Generally, F. sporotrichioides has higher chlamydospore abundance, longer chlamydospore chain, and production rapidity compared to F. graminearum in both abiotic and biotic treatments. However, biocontrol bacteria and mycoparasite posed minimal effects on chlamydospore formation, as compared to abiotic stressors, thus controlling the Fusaria but not triggering them to generate chlamydospores as protection shields.     

Effect of heavy metals and temperature on the oxalate oxidase activity and lignification of metaxylem vessels in barley roots

The effect of Cd on oxalate oxidase (OxO) activity and its localisation were analysed in barley root. In Cd-treated roots OxO activity was strongly induced in the region 2–4 mm behind the root tip and in the area toward the root base. In situ analyses showed that Cd-induced OxO activity was localised to the cell wall (CW) of early metaxylem vascular bundles and surrounding parenchyma cells and was accompanied by lignification of metaxylem vessels. OxO activation was also observed during treatment with other heavy metals (HMs), salt treatment and at elevated non-optimal temperature. In contrast to HM activation of OxO and lignification, high temperature and NaCl indeed activated OxO but did not induce lignification of metaxylem vessels. These results suggest that oxalate oxidase as an H₂O₂-generating enzyme is activated in response to several stresses, however the ectopic lignification of metaxylem vessels is activated specifically by HMs. This HM-induced premature root xylogenesis due to ectopic lignification of metaxylem vessels probably causes shortening of the root elongation zone and therefore a reduction in root growth.     

Impact of competition on plant performances along a flooding gradient: a multi‐species experiment

Question: 1. How do the competitive response and the importance of competition vary between species and along a flooding gradient? 2. How does the role of competition in constraining species distribution limits along the gradient vary between lower and upper limits? Location: A 1‐ha meadow within the Alzette floodplain in Luxembourg. Methods: Competitive response and importance of competition were assessed on seven meadow species differing in their tolerance to flooding. Species were cultured in monocultures and in mixtures, in three water treatments reflecting the wet, the middle and the dry end of a natural flooding gradient. We developed two models based on a multiple regression in order to express each component of competition as a function of the neighbour biomass. Results: Five species showed variations in their competitive response across water treatments; however, these species achieved either their highest or their worst competitive response in their optimal water treatment (i.e. the treatment in which the species had the highest biomass in monoculture). Competition was more important for the flood‐tolerant species in the dry treatment than for the flood‐intolerant species in the wet treatment. Conclusions: 1. Variations in species competitive responses along flooding gradients may be the result of either an amplified effect between competition and hydrological stresses, or a hierarchical effect of stress over competition. 2. The role of competition is more important in constraining the upper distribution limits of the flood‐tolerant species than the lower limits of the flood‐intolerant species along flooding gradients.     

Optimal hurricane overwash thickness for maximizing marsh resilience to sea level rise

The interplay between storms and sea level rise, and between ecology and sediment transport governs the behavior of rapidly evolving coastal ecosystems such as marshes and barrier islands. Sediment deposition during hurricanes is thought to increase the resilience of salt marshes to sea level rise by increasing soil elevation and vegetation productivity. We use mesocosms to simulate burial of Spartina alterniflora during hurricane‐induced overwash events of various thickness (0–60 cm), and find that adventitious root growth within the overwash sediment layer increases total biomass by up to 120%. In contrast to most previous work illustrating a simple positive relationship between burial depth and vegetation productivity, our work reveals an optimum burial depth (5–10 cm) beyond which burial leads to plant mortality. The optimum burial depth increases with flooding frequency, indicating that storm deposition ameliorates flooding stress, and that its impact on productivity will become more important under accelerated sea level rise. Our results suggest that frequent, low magnitude storm events associated with naturally migrating islands may increase the resilience of marshes to sea level rise, and in turn, slow island migration rates. Synthesis: We find that burial deeper than the optimum results in reduced growth or mortality of marsh vegetation, which suggests that future increases in overwash thickness associated with more intense storms and artificial heightening of dunes could lead to less resilient marshes.     

NAC转录因子在植物抗病和抗非生物胁迫反应中的作用

NAC转录因子是植物特有的一类转录因子,其共同特点是在N端含有一段高度保守、由约150个氨基酸组成的NAC结构域,而C端为高度变异的转录调控区。研究表明,NAC转录因子不仅参与植物生长发育的调控,而且在植物抗逆反应中具有重要的调控作用。文章着重介绍NAC转录因子在植物抗逆反应中的作用及其调控机制,并简要讨论NAC转录因子生物学功能的研究方向。     

不同胁迫预处理对水稻幼苗抗冷性和抗旱性的影响

水稻幼苗干旱预处理8小时后,转入低温(8～10℃),其抗冷性比未处理的高。0.1mol/L Nacl溶液盐预处理24小时,也提高水稻幼苗的抗冷性。低温3天,水稻幼苗叶片积累大量的脱落酸,此时将幼苗转至干旱环境下,抗旱性也大大提高。这说明水稻幼苗具有交叉适应能力,而脱落酸在交叉适应中起着重要的调节作用。     

Signal convergence through the lenses of MAP kinases: paradigms of stress and hormone signaling in plants

Common mechanisms plants use to translate the external stimuli into cellular responses are the activation of mitogen-activated protein kinase (MAPK) cascade. These MAPK cascades are highly conserved in eukaryotes and consist of three subsequently acting protein kinases, MAP kinase kinase kinase (MAPKKK), MAP kinase kinase (MAPKK) and MAP kinase (MAPK) which are linked in various ways with upstream receptors and downstream targets. Plant MAPK cascades regulate numerous processes, including various environmental stresses, hormones, cell division and developmental processes. The number of MAPKKs in Arabidopsis and rice is almost half the number of MAPKs pointing important role of MAPKKs in integrating signals from several MAPKKKs and transducing signals to various MAPKs. The cross talks between different signal transduction pathways are concentrated at the level of MAPKK in the MAPK cascade. Here we discussed the insights into MAPKK mediated response to environmental stresses and in plant growth and development.     

rpoS基因在肠杆菌CGMCC 5087响应环境胁迫中的功能

[背景]苯乙醇(2-Phenylethanol,2-PE)是一种具有玫瑰香气味的高级香料添加剂,被广泛应用于香水、化妆品、食品和医药等领域.目前,利用工程菌合成苯乙醇有很好的应用前景.我们分离到一株肠杆菌(Enterobactersp.)CGMCC 5087,其可以通过苯丙酮酸途径合成2-PE.然而该菌的生长受到不同环...