Chlorophyll fluorescence induction and estimation of plant resistance to stress factors

The usage of chlorophyll fluorescence induction (CFI) for estimating various types of plant resistance (primary, general, initial, adaptive) to stress factors is reviewed. The necessity of ontogenetic approach (considering the age-specific properties of the photosynthetic apparatus) in determining general and adaptive resistance of plants to prolonged action of stress factors by the CFI method is argued. In the plant Cucumbis sativus L., the possibility is shown of using age-specific qualitative and quantitative traits of leaf CFI (changes in the shape of chlorophyll fluorescence induction curves and in the dynamics of CFI parameters in the course of leaf ontogeny) for comparative study of differences between fully active and stressed plants. Possible criteria are suggested for estimating the effect of outer stress factors by the presence or absence of a steady-state phase in the dynamics of CFI parameters during leaf ontogeny. It is also suggested to use the duration of the steady-state phase following the termination of leaf growth (estimated by the dynamics of the slow phase of CFI as the ratio of fluorescence intensity at the peak P and the steady-state fluorescence intensity, Fp/Fs, or as the viability index Rfd) and the variability of CFI parameters during this period as qualitative estimates of plant resistance to prolonged action of stress factors.     

脱落酸衍生物及其类似物研究进展

脱落酸是一种广泛存在于植物体内的植物激素,它与植物离层形成、诱导休眠、抑制发芽、促进器官衰老和脱落及增强抗逆性等密切相关.本文就其衍生物及类似物的研究做一概要综述,并对脱落酸的衍生化及结构改造与生物活性关系做了综合评价,从目前的情况来看,对8'或9'位甲基的衍生化是相对比较成功的,其中出现了一些活性较高的化合物,这也是近年来ABA衍生化研究的热点.     

脱落酸衍生物及其类似物研究进展

脱落酸是一种广泛存在于植物体内的植物激素,它与植物离层形成、诱导休眠、抑制发芽、促进器官衰老和脱落及增强抗逆性等密切相关。本文就其衍生物及类似物的研究做一概要综述,并对脱落酸的衍生化及结构改造与生物活性关系做了综合评价,从目前的情况来看,对8'或9'位甲基的衍生化是相对比较成功的,其中出现了一些活性较高的化合物,这也是近年来ABA衍生化研究的热点。     

Specificity of induced resistance in wild radish: causes and consequences for two specialist and two generalist caterpillars

Inducible plant resistance against herbivores is becoming a paradigm of plant–herbivore ecology. Fundamental to understanding induced resistance and its evolutionary ecology is specificity of "induction" and "effects". Specificity in the induction of resistance refers to whether plant damage by various herbivores causes the same response in plants. Specificity in the effects of induced resistance refers to whether induction has the same consequences (i.e., reduced preference or performance) for various herbivores. I examined both specificity of induction and effect employing four lepidopteran herbivores and wild radish plants, a system for which fitness benefits and costs of induction have been documented for the plant. Variation in the specificity of induction and effects of induced plant resistance was found; however, this variation was not associated with diet specialization in the herbivores (i.e., specialists vs generalists). Induction caused by Plutella (specialist) and Spodoptera (generalist) resulted in general resistance to all of the herbivores, induction caused by Pieris (specialist) induced resistance only to Spodoptera (generalist) and Pieris , and plant damage by Trichoplusia (generalist) failed to induce resistance and reduce the performance of any of the herbivores. To the contrary, plants damaged by Trichoplusia supported enhanced growth of subsequently feeding Trichoplusia compared to uninduced controls. These results add a novel level of complexity to interactions between plants and leaf chewing caterpillars. Within the same guild of feeders, some herbivores cause strong induced resistance, no induced resistance, or induced susceptibility. Similarly, caterpillar species were variable in the level to which induced resistance affected their performance. Such interactions limit the possibility of pairwise coevolution between plants and herbivores, and suggest that coevolution can only be diffuse.     

Induction of Phytohemagglutinin Activity by Arachidonic Acid in in vitro Potato Plants

Tube-grown potato (Solanum tuberosum L., cv. Nevskii) plants treated with arachidonic acid (AA) were used as a model to study the activity of phytohemagglutinins (PHA) during induction of the plant antiviral defense system. Plant treatment with 10^–8 M AA and also their inoculation with potato viruses X, Y, and M resulted in the increased activity of PHAs in potato shoots. The inducer of antiviral resistance behaved as a modulator of the PHA activity providing for its various levels during the development of viral infection. During the development of AA-induced systemic resistance, the level of phytohemagglutinin activity did not essentially depend on the nature of the viral pathogen. We suggested that the mechanism of AA-induced plant antiviral defense was connected with changes in the PHA activity.     

Sodium fluoride inhibits HSP synthesis in heat-stressed cultured cells of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Fluorine is a component of atmospheric emissions in industrial areas. It negatively affects plant development and weakens the defense systems, thus making plants vulnerable to extreme environmental conditions. The heat shock proteins (HSP) are known to promote the plant resistance to various biotic and abiotic stresses. We studied the action of sodium fluoride (NaF) on growth, viability, respiration, transmembrane electric potential at the inner mitochondrial membrane (mtΔΨ), the development of induced thermotolerance, and HSP synthesis in the cell culture of Arabidopsis thaliana (L) Heynh (accession Columbia). The treatment with 20 mM NaF (for 120 min) had no negative influence on viability of the cell culture but inhibited the development of induced thermotolerance and suppressed the induction of HSP (Hsp101 and Hsp17.6) synthesis during mild heat stress (37°C). At the same time, the treatment with NaF inhibited respiration and suppressed the increase in mtΔΨ induced by mild heat stress. Hence, the negative impact of NaF on plants might arise from its ability to inhibit synthesis of stress proteins indispensible for plant adaptation to changing environmental conditions.     

Polyether ionophores—promising bioactive molecules for cancer therapy

The natural polyether ionophore antibiotics might be important chemotherapeutic agents for the treatment of cancer. In this article, the pharmacology and anticancer activity of the polyether ionophores undergoing pre-clinical evaluation are reviewed. Most of polyether ionophores have shown potent activity against the proliferation of various cancer cells, including those that display multidrug resistance (MDR) and cancer stem cells (CSC). The mechanism underlying the anticancer activity of ionophore agents can be related to their ability to form complexes with metal cations and transport them across cellular and subcellular membranes. Increasing evidence shows that the anticancer activity of polyether ionophores may be a consequence of the induction of apoptosis leading to apoptotic cell death, arresting cell cycle progression, induction of the cell oxidative stress, loss of mitochondrial membrane potential, reversion of MDR, synergistic anticancer effect with other anticancer drugs, etc. Continued investigation of the mechanisms of action and development of new polyether ionophores and their derivatives may provide more effective therapeutic drugs for cancer treatments.     

局部力学刺激对黄瓜系统抗病性的诱导

病原真菌在侵入植物细胞过程中,除了分泌化学物质外还通过物理挤压细胞产生力学作用.用压应力作为力学信号,研究了局部力学刺激对黄瓜系统抗病性的诱导.结果表明,力学刺激可以诱导黄瓜系统抗病性的产生.当细胞壁与质膜间的黏附被Arg-Gly-Asp(RGD)阻断后,力学刺激对黄瓜系统抗病性的诱导几乎完全被减除.通过薄层色谱和液相色谱分析,发现力学刺激可以使植保素含量明显增加.这表明黄瓜植保素的积累可能是力学刺激诱导其产生抗性的原因之一.而细胞壁与质膜间的黏附被RGD阻断后,力学刺激只能诱导植保素的部分积累.即力学刺激对植保素积累的诱导依赖于细胞膜与细胞壁间的黏附.     

多倍体植物抗逆性研究进展

许多逆境能诱导多倍体植物发生,并可能作为筛选压力推动多倍体的形成。多倍体植物具有细胞、器官巨大化的特点,但株型不一定巨大化。在几种主要逆境条件下(如低温、高温、干旱、盐碱、病害等),多倍体植物抗逆性往往增强。多倍体植物主要通过调整细胞大小和结构、调节生物膜系统、提高渗透调节物质含量、增强抗氧化系统活性、增加基因表达和通过表观遗传变化来增强抗逆性,但也有研究显示多倍体植物的抗逆性降低。多倍体植物的抗逆性还需要更深入和细致研究,才能阐明抗逆机理。该文对近年来国内外有关多倍体植物的形成、特征、抗逆性表现及其调控机制等方面的研究进展进行综述。     

Bacillus subtilis: A plant-growth promoting rhizobacterium that also impacts biotic stress

Plants encounter many biotic agents, such as viruses, bacteria, nematodes, weeds, and arachnids. These entities induce biotic stress in their hosts by disrupting normal metabolism, and as a result, limit plant growth and/or are the cause of plant mortality. Some biotic agents, however, interact symbiotically or synergistically with their host plants. Some microbes can be beneficial to plants and perform the same role as chemical fertilizers and pesticides, acting as a biofertilizer and/or biopesticide. Plant growth promoting rhizobacteria (PGPR) can significantly enhance plant growth and represent a mutually helpful plant-microbe interaction. Bacillus species are a major type of rhizobacteria that can form spores that can survive in the soil for long period of time under harsh environmental conditions. Plant growth is enhanced by PGPR through the induction of systemic resistance, antibiosis, and competitive omission. Thus, the application of microbes can be used to induce systemic resistance in plants against biotic agents and enhance environmental stress tolerance. Bacillus subtilis exhibits both a direct and indirect biocontrol mechanism to suppress disease caused by pathogens. The direct mechanism includes the synthesis of many secondary metabolites, hormones, cell-wall-degrading enzymes, and antioxidants that assist the plant in its defense against pathogen attack. The indirect mechanism includes the stimulation of plant growth and the induction of acquired systemic resistance. Bacillus subtilis can also solubilize soil P, enhance nitrogen fixation, and produce siderophores that promote its growth and suppresses the growth of pathogens. Bacillus subtilis enhances stress tolerance in their plant hosts by inducing the expression of stress-response genes, phytohormones, and stress-related metabolites. The present review discusses the activity of B. subtilis in the rhizosphere, its role as a root colonizer, its biocontrol potential, the associated mechanisms of biocontrol and the ability of B. subtilis to increase crop productivity under conditions of biotic and abiotic stress.     

Autophagy and its role in plant abiotic stress management

Being unable to move, plants are regularly exposed to changing environmental conditions, among which various types of abiotic stress, such as heat, drought, salt, and so forth. These might have deleterious effects on plant performance and yield. Plants thus need to adapt using appropriate stress responses. One of the outcomes of abiotic stress is the need to degrade and recycle damaged proteins and organelles. Autophagy is a conserved eukaryotic mechanism functioning in the degradation of proteins, protein aggregates, and whole organelles. It was previously shown to have a role in plant abiotic stress. This review will describe the current knowledge regarding the involvement of autophagy in plant abiotic stress response, mechanisms functioning in autophagy induction during stress, and possible direction for future research.     

The yeast Pdr15p ATP-binding cassette (ABC) protein is a general stress response factor implicated in cellular detoxification

ATP-binding cassette (ABC) transporters play important roles in drug efflux, but some may also function in cellular detoxification. The Pdr15p ABC protein is the closest homologue of the multidrug efflux transporter Pdr5p, which mediates pleiotropic drug resistance to hundreds of unrelated compounds. In this study, we show that the plasma membrane protein Pdr15p displays limited drug transport capacity, mediating chloramphenicol and detergent tolerance. Interestingly, Pdr15p becomes most abundant when cells exit the exponential growth phase, whereas its closest homologue, Pdr5p, disappears after exponential growth. Furthermore, in contrast to Pdr5p, Pdr15p is strongly induced by various stress conditions including heat shock, low pH, weak acids, or high osmolarity. PDR15 induction bypasses the Pdr1p/Pdr3p regulators but requires the general stress regulator Msn2p, which directly decorates the stress response elements in the PDR15 promoter. Remarkably, however, Pdr15p induction bypasses upstream components of the high osmolarity glycerol (HOG) pathway including the Hog1p and Pbs2p kinases as well as the dedicated HOG cell surface sensors. Our data provide evidence for a novel upstream branch of the general stress response pathway activating Msn2p. In addition, the results demonstrate a cross-talk between stress response and the pleiotropic drug resistance network.     

Effects of salicylic acid pre-treatment on cadmium and/or UV-B stress in soybean seedlings

The present study examined the effect of salicylic acid (SA) pre-treatment on soybean seedlings exposed to cadmium and/or UV-B stress. Dry mass, pigment content, net photosynthetic rate (P_N), stomatal conductance (g_s), and transpiration rate (E) were decreased by the Cd and/or UV-B stress. SA alleviated the adverse effects of Cd and/or UV-B on growth, pigment content, PN, and gs, but did not mitigate the inhibitory effect of Cd/UV-B on E, or that of Cd on chlorophyll fluorescence parameters. Cd and/or UV-B induced oxidative stress and increased lipid peroxidation that was significantly decreased by SA pre-treatment. The Cd and/or UV-B increased superoxide dismutase (SOD) activity, decreased peroxidase (POD) activity, and catalase (CAT) activity was mostly unaltered. SA might act as one of the potential antioxidants as well as a stabilizer of membrane integrity to improve plant resistance to the Cd and/or UV-B stress.     

Ontogenetic approach to the assessment of plant resistance to prolonged stress using chlorophyll fluorescence induction method

The review deals with objective reasons that limit the use of chlorophyll fluorescence induction kinetics (Chl FIK) method in plant ecology. Based on the ontogenetic approach (analysis and comparison of the dynamics of the Chl fluorescence ratio F_p/F_s and physiological characteristics of plant leaves in ontogeny) possible criteria for the estimation of general plant resistance of photosynthetic apparatus (PSA) to prolonged stress affects are proposed. One of these criteria is the presence or absence of a steady-state phase in the dynamics of Chl fluorescence ratio F_p/F_s (or R_fd) of plant leaves after they stop growing. We also propose to use the duration of the steady-state phase and variability of Chl fluorescence ratios R_fd and F_p/F_s in this period for quantitative assessment of plant PSA resistance to prolonged stress during plant leaf ontogeny. The paper is dedicated to memory of Prof. F.Ya. Sid’ko.