Endophytes from wild cereals protect wheat plants from drought by alteration of physiological responses of the plants to water stress

Endophytes contribute to plant performance, especially under harsh conditions. We therefore hypothesized that wild plants have retained beneficial endophytes that are less abundant or not present in related crop plants. To test this hypothesis, we selected two endophytes that were found in Sharon goatgrass, an ancestor of wheat, and tested their effect on bread wheat. Both endophytes infected wheat and improved sustainability and performance under water-limited conditions. To determine how the endophytes modify plant development, we measured parameters of plant growth and physiological status and performed a comparative metabolomics analysis. Endophyte-treated wheat plants had reduced levels of stress damage markers and reduced accumulation of stress-adaptation metabolites. Metabolomics profiling revealed significant differences in the response to water stress of endophyte-treated plants compared with untreated plants. Our results demonstrate the potential of endophytes from wild plants for improvement of related crops and show that the beneficial effects of two endophytes are associated with alteration of physiological responses to water-limited conditions.     

How plants protect themselves from ultraviolet-B radiation stress

Ultraviolet-B (UV-B) radiation has a wavelength range of 280–315 nm. Plants perceive UV-B as an environmental signal and a potential abiotic stress factor that affects development and acclimation. UV-B regulates photomorphogenesis including hypocotyl elongation inhibition, cotyledon expansion, and flavonoid accumulation, but high intensity UV-B can also harm plants by damaging DNA, triggering accumulation of reactive oxygen species, and impairing photosynthesis. Plants have evolved “sunscreen” flavonoids that accumulate under UV-B stress to prevent or limit damage. The UV-B receptor UV RESISTANCE LOCUS 8 (UVR8) plays a critical role in promoting flavonoid biosynthesis to enhance UV-B stress tolerance. Recent studies have clarified several UVR8-mediated and UVR8-independent pathways that regulate UV-B stress tolerance. Here, we review these additions to our understanding of the molecular pathways involved in UV-B stress tolerance, highlighting the important roles of ELONGATED HYPOCOTYL 5, BRI1-EMS-SUPPRESSOR1, MYB DOMAIN PROTEIN 13, MAP KINASE PHOSPHATASE 1, and ATM- and RAD3-RELATED. We also summarize the known interactions with visible light receptors and the contribution of melatonin to UV-B stress responses. Finally, we update a working model of the UV-B stress tolerance pathway.

Recent findings that update our understanding of the molecular pathway for ultraviolet-B radiation stress responses in plants are summarized.     

Endophytic fungi of grasses protect other plants from aphid herbivory

Microbial plant symbionts are widely spread in nature changing the way their hosts interact with their environment. Neotyphodium fungal endophytes (Clavicipitaceae) are grass symbionts known by their production of alkaloids, toxic for herbivores. Here, we hypothesized that endophytes confer associational protection to non-host plants and change emission of host volatile-compounds. In an outdoor mesocosm experiment, we examined aphid infestation on Trifolium repens plants, in response to Neotyphodium occultans presence in neighbouring Lolium multiflorum. Contrasting levels of Rhizobium were generated in T. repens plants considering that symbiosis with N₂-fixers would influence herbivore abundance. Aphid infestation increased responding to symbiotic status of T. repens plants, when surrounded by non-symbiotic L. multiflorum plants. Endophytes modified the volatile imprints of L. multiflorum plants measured by an electronic nose, suggesting a potential mechanism to benefit neighbours. This associational protection constitutes a new mutualism trait of grass-endophyte symbiosis, becoming a non-private benefit available to other community partners.     

Potential of animal myeloperoxidase to protect plants from pathogens.

The effect of animal myeloperoxidase (EC 1.11.1.7) on the viability of a plant pathogen was determined. Lethality of hydrogen peroxide to germinating spores of Aspergillus flavus increased 90-fold enzymically. Singlet oxygen was present but hypochlorite accounted for two-thirds of the increase. The results indicate myeloperoxidase could improve microbial resistance in plants, perhaps transgenically.     

微生物帮助烟草抗旱的机理及其应用

干旱是中国烟草种植业面临的较为严重的非生物胁迫.很多与植物共生或联合的根际微生物能帮助植物避旱和耐旱.微生物能通过菌丝吸水并转运到植物,通过产生植物激素或改变植物内源激素的平衡来促进根发育和伸长,或诱导叶片关闭气孔,促进根吸水和减少叶片散失水分来避旱.微生物能通过调整不同激素介导的信号通路,诱导植物产生系统抗逆性,促进植物细胞产生渗透保护剂、抗氧化物和活性氧清除剂而耐旱.微生物还能帮助植物吸收营养,以支持植物在干旱胁迫下的代谢和生长.本文关注丛枝菌根真菌、模式内生真菌印度梨形孢和根际促植物生长细菌帮助烟草和番茄等植物抗旱的机理,探讨如何在烟草育苗和栽培中应用有益微生物来帮助烟草抗旱.     

Inducing drought tolerance in plants: Recent advances

Undoubtedly, drought is one of the prime abiotic stresses in the world. Crop yield losses due to drought stress are considerable. Although a variety of approaches have been used to alleviate the problem of drought, plant breeding, either conventional breeding or genetic engineering, seems to be an efficient and economic means of tailoring crops to enable them to grow successfully in drought-prone environments. During the last century, although plant breeders have made ample progress through conventional breeding in developing drought tolerant lines/cultivars of some selected crops, the approach is, in fact, highly time-consuming and labor- and cost-intensive. Alternatively, marker-assisted breeding (MAB) is a more efficient approach, which identifies the usefulness of thousands of genomic regions of a crop under stress conditions, which was, in reality, previously not possible. Quantitative trait loci (QTL) for drought tolerance have been identified for a variety of traits in different crops. With the development of comprehensive molecular linkage maps, marker-assisted selection procedures have led to pyramiding desirable traits to achieve improvements in crop drought tolerance. However, the accuracy and preciseness in QTL identification are problematic. Furthermore, significant genetic × environment interaction, large number of genes encoding yield, and use of wrong mapping populations, have all harmed programs involved in mapping of QTL for high growth and yield under water limited conditions. Under such circumstances, a transgenic approach to the problem seems more convincing and practicable, and it is being pursued vigorously to improve qualitative and quantitative traits including tolerance to biotic and abiotic stresses in different crops. Rapid advance in knowledge on genomics and proteomics will certainly be beneficial to fine-tune the molecular breeding and transformation approaches so as to achieve a significant progress in crop improvement in future. Knowledge of gene regulation and signal transduction to generate drought tolerant crop cultivars/lines has been discussed in the present review. In addition, the advantages and disadvantages as well as future prospects of each breeding approach have also been discussed.     

Indigenous arbuscular mycorrhizal fungal assemblages protect grassland host plants from pathogens

Plant roots can establish associations with neutral, beneficial and pathogenic groups of soil organisms. Although it has been recognized from the study of individual isolates that these associations are individually important for plant growth, little is known about interactions of whole assemblages of beneficial and pathogenic microorganisms associating with plants.We investigated the influence of an interaction between local arbuscular mycorrhizal (AM) fungal and pathogenic/saprobic microbial assemblages on the growth of two different plant species from semi-arid grasslands in NE Germany (Mallnow near Berlin). In a greenhouse experiment each plant species was grown for six months in either sterile soil or in sterile soil with one of three different treatments: 1) an AM fungal spore fraction isolated from field soil from Mallnow; 2) a soil pathogen/saprobe fraction consisting of a microbial community prepared with field soil from Mallnow and; 3) the combined AM fungal and pathogen/saprobe fractions. While both plant species grew significantly larger in the presence of AM fungi, they responded negatively to the pathogen/saprobe treatment. For both plant species, we found evidence of pathogen protection effects provided by the AM fungal assemblages. These results indicate that interactions between assemblages of beneficial and pathogenic microorganisms can influence the growth of host plants, but that the magnitude of these effects is plant species-specific.     

Probiotics: from bench to market

"Probiotics: From Bench to Market" was a one-day conference convened by the New York Academy of Sciences on June 11, 2010, with the goal of stimulating discussion of the physiological effects of probiotics on the gastrointestinal, nervous, and immune systems. The program included speakers from academia, industry, and government to give conference participants a full understanding of the state of the field of probiotics. The overall goal of the program was to increase communication and collaboration among these groups to advance probiotic research and probiotic contributions to public health. The conference was divided into three sessions and included both oral and visual presentations as well as panel discussions.     

Engineering drought and salinity tolerance in plants: lessons from genome-wide expression profiling in Arabidopsis

World food security is increasingly dependent on continuous crop improvement and, in particular, the development of crops with increased drought and salinity tolerance. The completed genomic sequence of the model plant Arabidopsis thaliana and the development of whole-genome microarrays, together with increasing repositories of publicly available data and data analysis tools, have opened new avenues to genome-wide systemic analysis of plant stress responses. Here we outline examples of how this full-genome expression profiling can contribute to our understanding of complex stress responses and the identification and evaluation of novel transgenes that could hold the key to the development of commercially viable and sustainable crop plants.     

Short-term damage-induced increases in tobacco alkaloids protect plants

Summary Leaf damage significantly increases the alkaloid content in undamaged leaves on damaged field-grown wild tobacco plants. Although field-grown pot-bound plants fail to exhibit the same damage-induced increase in alkaloid content, the ability to respond to leaf damage is restored 6 days after removing plants from their pots. Freshly hatched Manduca sexta larvae reared individually in the laboratory on the high-alkaloid foliage of damaged plants released from their pots gain less weight and eat less (57.2% and 45.7% of controls, respectively) than larvae fed low-alkaloid foliage from undamaged released plants. Moreover, larvae grow equally well on the foliage of damaged and undamaged pot-bound plants. The higher chlorophyll contents characteristic of damaged released plants did not negate the effects of the increased alkaloid contents on larval growth. Undamaged leaves from undamaged field-grown plants stem-fed nicotine solutions had elevated leaf nicotine and nornicotine contents. Larvae reared on these artificially induced leaves gain only 38.5% of the weight gained by larvae reared on low-alkaloid foliage. These results demonstrate that damage-induced increases in leaf alkaloids protect induced foliage from attack and are sufficient to explain the decreased growth of caterpillars on the foliage of damaged plants.     

Identification of novel aphid-killing bacteria to protect plants

Aphids, including the peach-potato aphid, Myzus persicae, are major insect pests of agriculture and horticulture, and aphid control measures are limited. There is therefore an urgent need to develop alternative and more sustainable means of control. Recent studies have shown that environmental microbes have varying abilities to kill insects. We screened a range of environmental bacteria isolates for their abilities to kill target aphid species. Tests demonstrated the killing aptitude of these bacteria against six aphid genera (including Myzus persicae). No single bacterial strain was identified that was consistently toxic to insecticide-resistant aphid clones than susceptible clones, suggesting resistance to chemicals is not strongly correlated with bacterial challenge. Pseudomonas fluorescens PpR24 proved the most toxic to almost all aphid clones whilst exhibiting the ability to survive for over three weeks on three plant species at populations of 5–6 log CFU cm⁻² leaf. Application of PpR24 to plants immediately prior to introducing aphids onto the plants led to a 68%, 57% and 69% reduction in aphid populations, after 21 days, on Capsicum annuum, Arabidopsis thaliana and Beta vulgaris respectively. Together, these findings provide new insights into aphid susceptibility to bacterial infection with the aim of utilizing bacteria as effective biocontrol agents.     

Some physiological and morphological characteristics of citrus plants for drought resistance

Tolerance and avoidance mechanisms to drought stress were studied in 6-month-old plants of Newhall orange (Citrus sinensis (L.) Osbeck) and Ellendale tangor (orange × mandarin hybrid) (Citrus sinensis (L) Osbeck × Citrus reticulata Blanco) during a drought/rewatering cycle under controlled conditions. Drought stress did not promote osmotic adjustment, while elastic adjustment (tissue elasticity increase) was noted in stressed orange and tangor plants. Both citrus plants showed a parallel decrease in leaf conductance (g₁) and leaf water potential (Ψ₁) under water stress. Tangor plants had a more efficient water conservative strategy than orange, based on the characteristics of canopy architecture (lower canopy area and a more closed canopy with leaves nearly vertically oriented) together with a significant decrease in cuticular transpiration rates (TRc) under stress.     

Dermal bioactives from lactobacilli and bifidobacteria

Lactobacilli and bifidobacteria are the most common genera of probiotics with documented potentials on gut health. Recent studies have suggested that such potentials can be extended beyond gut well-being, such as that of dermal health. Our present study aimed to evaluate the production of bioactives that are essential for skin defense, such as lipoteichoic acid, peptidoglycan, hyaluronic acid, sphingomyelinase, lactic acid, acetic acid, and diacetyl, from lactobacilli and bifidobacteria grown in milk. All strains studied showed the presence of LTA in the cell wall fraction, with higher amounts from Lactobacillus rhamnosus FTDC 8313 and Bifidobacterium longum BL 8643 than other strains studied. Meanwhile, all strains studied showed equal concentrations of cell wall peptidoglycan. Our results showed that all strains studied were capable of producing hyaluronic acid, with higher production by lactobacilli than bifidobacteria. Production of diacetyl was more prevalent from strains of lactobacilli, while bifidobacteria produced higher amounts of acetic acid. Strains of lactobacilli and bifidobacteria studied also produced acid and neutral sphingomyelinase, an enzyme that generates ceramides and subsequent development of physical barriers in the stratum corneum. Our current findings show that bioactive and inhibitive extracts are produced from the fermentation of lactobacilli and bifidobacteria in milk, with potentials for dermal applications.     

Spines protect plants against browsing by small climbing mammals

The presence of spines on woody plants has been shown to limit the loss of foliage to large mammalian browsers by restricting both bite size and biting rate. We tested the hypothesis that plant spines are also an effective defense against browsing by small mammals, such as rodents, that climb within the canopy of shrubs to harvest fruits, seeds, and foliage. Tame southern plains woodrats (Neotoma micropus) were allowed to harvest raisins impaled on the branches of blackbrush shrubs (Acacia rigidula Benth.) in five categories of spinescence: naturally spineless, moderately spiny, or very spiny branches, and moderately spiny and very spiny branches with the spines removed. Plant spinescence significantly reduced the woodrats foraging efficiency (P = 0.0001). Although plant spines are generally thought to be an evolved defense against browsing by ungulate herbivores, they may also reduce browsing by small mammals. Received: 15 May 1997 / Accepted: 29 August 1997     

Predators indirectly protect tundra plants by reducing herbivore abundance

The role of predators in controlling herbivores and indirectly affecting plant abundance is controversial, and some have argued that such trophic cascades are rare in terrestrial habitats. To examine the potential of trophic cascades in a shrubby tundra ecosystem, vole densities, plant damage and plant cover were examined in areas with and without small mammal predators. On islands without predators, vole densities and plant damage were upto five times higher compared with predator-rich mainland habitats. As a consequence, the abundance of three out of five dwarf shrub species was substantially reduced on predator-free islands, providing evidence for strong cascading effects in a rather large-scale terrestrial system. Herbs on the other hand were not affected by the increased herbivory on islands. This suggests that the strength of trophic cascades also depends on the interaction between plant type and seasonality.