Impact of flumioxazin herbicide on growth and carbohydrate physiology in Vitis vinifera L

The impact of flumioxazin herbicide on in vitro-grown grapevine ( Vitis vinifera L. cv. Chardonnay) was investigated. The herbicide treatments (1, 10 or 100 micro M flumioxazin in MM medium) had a negative impact on photosynthesis, as revealed by a reduction in foliar chlorophyll and carotenoid contents, gas exchanges and alteration in plastid structure and, consequently, resulted in a strong inhibition of plantlet growth. Surprisingly, soluble sugars and starch accumulated in all organs, suggesting a stimulation of sugar uptake from the medium. Moreover, photosynthetic activity and starch content partially recovered within 3 weeks of treatment at the weakest herbicide concentration. These results provide new insights into the physiological responses of non-target crops to flumioxazin, showing that flumioxazin is active in photosynthetic tissues of the non-target grapevine via root uptake, which is contrary to what is mentioned in the literature, and that the in vitro-grown plantlet is a good model for investigating the physiological effects of pesticides on crop species.     

Arabidopsis sensitivity to protein synthesis inhibitors depends on 26S proteasome activity

The 26S proteasome (26SP), the central protease of the ubiquitin-dependent proteolysis pathway, controls the regulated proteolysis of functional proteins and the removal of misfolded and damaged proteins. In Arabidopsis, cellular and stress response phenotypes of a number of mutants with partially impaired 26SP function have been reported. Here, we describe the responses of proteasome mutants to protein synthesis inhibitors. We show that the rpt2a-3, rpn10-1 and rpn12a-1 mutants are hypersensitive to the antibiotic hygromycin B, and tolerant to the translation inhibitor cycloheximide (CHX) and herbicide l-phosphinothricin (PPT). In addition to the novel mechanism for herbicide tolerance, our data suggests that the combination of hygromycin B, CHX and PPT growth-response assays could be used as a facile diagnostic tool to detect altered 26SP function in plant mutants and transgenic lines.     

Evidence for a role of salicylic acid in the oxidative damage generated by NaCl and osmotic stress in Arabidopsis seedlings.

Previous studies have shown that salicylic acid (SA) is an essential component of the plant resistance to pathogens. We now show that SA plays a role in the plant response to adverse environmental conditions, such as salt and osmotic stresses. We have studied the responses of wild-type Arabidopsis and an SA-deficient transgenic line expressing a salicylate hydroxylase (NahG) gene to different abiotic stress conditions. Wild-type plants germinated under moderate light conditions in media supplemented with 100 mM NaCl or 270 mM mannitol showed extensive necrosis in the shoot. In contrast, NahG plants germinated under the same conditions remained green and developed true leaves. The lack of necrosis observed in NahG seedlings under the same conditions suggests that SA potentiates the generation of reactive oxygen species in photosynthetic tissues during salt and osmotic stresses. This hypothesis is supported by the following observations. First, the herbicide methyl viologen, a generator of superoxide radical during photosynthesis, produced a necrotic phenotype only in wild-type plants. Second, the presence of reactive oxygen-scavenging compounds in the germination media reversed the wild-type necrotic phenotype seen under salt and osmotic stress. Third, a greater increase in the oxidized state of the glutathione pool under NaCl stress was observed in wild-type seedlings compared with NahG seedlings. Fourth, greater oxidative damage occurred in wild-type seedlings compared with NahG seedlings under NaCl stress as measured by lipid peroxidation. Our data support a model for SA potentiating the stress response of the germinating Arabidopsis seedling.     

利用蛋白质组学技术揭示的植物高温胁迫响应机制

高温是限制植物生长和产量的主要非生物胁迫因子.近年来,蛋白质组学研究为我们从系统生物学水平深入认识植物高温胁迫应答的复杂的分子机制提供了重要信息.目前,已经分析了模式植物拟南芥、主要粮食作物(大豆、水稻和小麦)、耐热植物(匍匐剪股颖、马齿苋、假虎刺),以及野生毛葡萄、胡杨、苜蓿、半夏等应答高温胁迫过程中的蛋白质组变化特征.这些研究共鉴定到838种响应高温胁迫的蛋白质,其中534种蛋白质表达受到高温诱导,304种蛋白质表达受到抑制.本文整合分析了上述植物在应对不同程度高温胁迫(30～45 ℃处理0～10 d)时蛋白质表达模式的变化特征,为解释高温胁迫应答网络体系中重要的信号与代谢通路(如：信号转导、胁迫防御、糖类与能量代谢、光合作用、转录、蛋白质合成与命运、膜与转运等)的变化提供了证据和线索,为深入认识植物应答高温胁迫的分子调控机制奠定了坚实的基础.     

Perturbed lignification impacts tree growth in hybrid poplar--a function of sink strength, vascular integrity, and photosynthetic assimilation

The effects of reductions in cell wall lignin content, manifested by RNA interference suppression of coumaroyl 3'-hydroxylase, on plant growth, water transport, gas exchange, and photosynthesis were evaluated in hybrid poplar trees (Populus alba x grandidentata). The growth characteristics of the reduced lignin trees were significantly impaired, resulting in smaller stems and reduced root biomass when compared to wild-type trees, as well as altered leaf morphology and architecture. The severe inhibition of cell wall lignification produced trees with a collapsed xylem phenotype, resulting in compromised vascular integrity, and displayed reduced hydraulic conductivity and a greater susceptibility to wall failure and cavitation. In the reduced lignin trees, photosynthetic carbon assimilation and stomatal conductance were also greatly reduced, however, shoot xylem pressure potential and carbon isotope discrimination were higher and water-use efficiency was lower, inconsistent with water stress. Reductions in assimilation rate could not be ascribed to increased stomatal limitation. Starch and soluble sugars analysis of leaves revealed that photosynthate was accumulating to high levels, suggesting that the trees with substantially reduced cell wall lignin were not carbon limited and that reductions in sink strength were, instead, limiting photosynthesis.     

Stress effects of flumioxazin herbicide on grapevine (<Emphasis Type="Italic">Vitis vinifera</Emphasis> L.) grown in vitro

Among the herbicides used in vineyards, the pre-emergence soil-applied flumioxazin (FMX) is a recently synthesized molecule that inhibits chlorophyll biosynthesis in weed species. The aim of this work was to characterize the effects of FMX on non-target grapevine (Vitis vinifera L. cv. Chardonnay) plantlets grown in vitro. FMX treatment (from 1 to 100 M) represented a stress, as revealed by measurement of several parameters. Stem and leaves underwent dehydration and a decrease in both water- and osmotic-potential. Treated plantlets exhibited concomitant accumulation of soluble carbohydrates in all tissues and of free proline in stems and leaves. Moreover, FMX caused lipid peroxidation and electrolyte leakage in leaf tissues. These results indicate that the herbicide FMX is toxic for grapevine grown in vitro. In addition to inhibiting protoporphyrinogen IX oxidase, it causes water stress and membrane alteration in tissues and, as a consequence, generates the accumulation of carbohydrates and free proline.Abbreviations FMX Flumioxazin - MDA Malondialdehyde - PROTOX Protoporphyrinogen IX oxidase - TBARS Thiobarbituric acid reactive substances - TFAA Total free amino acids - TSS Total soluble sugarsCommunicated by S. Gleddie     

Heat shock proteins in animal neoplasms and human tumours—a comparison

Heat shock proteins (HSPs) are implicated in all phases of cancer from proliferation, impaired apoptosis and sustained angiogenesis to invasion and metastasis. The presence of abnormal HSP levels in several human tumours suggests that these proteins could be used as diagnostic and/or prognostic markers, whilst the direct correlation between HSP expression and drug resistance in neoplastic tissues means they could also be used to predict cancer response to specific treatment. HSPs have also been successfully targeted in clinical trials modifying their expression or chaperone activity. Preliminary studies in veterinary medicine have also demonstrated the presence of altered HSP expression in neoplasms, and the study of carcinogenesis and the role of HSPs in animal models will surely be an additional source of information for clinical cancer research.     

植物镉忍耐的分子机理

Cd是植物非必需的微量元素,对植物有很强的毒性.Cd抑制植物细胞生长,抑制氧化磷酸化,引发氧化胁迫,影响光合作用,损伤核仁和影响质膜ATP酶的活力.一些耐Cd植物通过诱导形成螯合肽、金属硫蛋白、植物应激蛋白等抵御Cd毒,也有的耐Cd植物则通过细胞壁固定、液泡分隔、腺体分泌等途径来抵御Cd毒.植物螯合肽合成酶(PCS)相关的一些基因已得到克隆.金属硫蛋白(MT)的克隆基因导入植物,使植物对Cd毒的抗性增加;植物胁迫蛋白可提高植物对Cd毒的抗性,Zn转运蛋白可运转Cd.修饰基因则通过影响主要基因提高植物对Cd的忍耐能力.野生型植物耐Cd毒是多基因控制的,而植物短期的Cd忍耐,则仅受一个或少数基因控制.     

Impairment of carbon metabolism induced by the herbicide glyphosate

The herbicide glyphosate reduces plant growth and causes plant death by inhibiting the biosynthesis of aromatic amino acids. The objective of this work was to determine whether glyphosate-treated plants show a carbon metabolism pattern comparable to that of plants treated with herbicides that inhibit branched-chain amino acid biosynthesis. Glyphosate-treated plants showed impaired carbon metabolism with an accumulation of carbohydrates in the leaves and roots. The growth inhibition detected after glyphosate treatment suggested impaired metabolism that impedes the utilization of available carbohydrates or energy at the expected rate. These effects were common to both types of amino acid biosynthesis inhibitors. Under aerobic conditions, ethanolic fermentative metabolism was enhanced in the roots of glyphosate-treated plants. This fermentative response was not related to changes in the respiratory rate or to a limitation of the energy charge. This response, which was similar for both types of herbicides, might be considered a general response to stress conditions.     

Proteomic analysis of rice leaves shows the different regulations to osmotic stress and stress signals

Following the idea of partial root-zone drying(PRD)in crop cultivation,the morphological and physiological responses to partial root osmotic stress(PROS)and whole root osmotic stress(WROS)were investigated in rice.WROS caused stress symptoms like leaf rolling and membrane leakage.PROS stimulated stress signals,but did not cause severe leaf damage.By proteomic analysis,a total of 58 proteins showed differential expression after one or both treatments,and functional classification of these proteins suggests that stress signals regulate photosynthesis,carbohydrate and energy metabolism.Two other proteins(anthranilate synthase and submergence-induced nickel-binding protein)were upregulated only in the PROS plants,indicating their important roles in stress resistance.Additionally,more enzymes were involved in stress defense,redox homeostasis,lignin and ethylene synthesis in WROS leaves,suggesting a more comprehensive regulatory mechanism induced by osmotic stress.This study provides new insights into the complex molecular networks within plant leaves involved in the adaptation to osmotic stress and stress signals.     

The plant-growth-promoting rhizobacterium Paenibacillus polymyxa induces changes in Arabidopsis thaliana gene expression: a possible connection between biotic and abiotic stress responses.

This paper addresses changes in plant gene expression induced by inoculation with plant-growth-promoting rhizobacteria (PGPR). A gnotobiotic system was established with Arabidopsis thaliana as model plant, and isolates of Paenibacillus polymyxa as PGPR. Subsequent challenge by either the pathogen Erwinia carotovora (biotic stress) or induction of drought (abiotic stress) indicated that inoculated plants were more resistant than control plants. With RNA differential display on parallel RNA preparations from P. polymyxa-treated or untreated plants, changes in gene expression were investigated. From a small number of candidate sequences obtained by this approach, one mRNA segment showed a strong inoculation-dependent increase in abundance. The corresponding gene was identified as ERD15, previously identified to be drought stress responsive. Quantification of mRNA levels of several stress-responsive genes indicated that P. polymyxa induced mild biotic stress. This suggests that genes and/or gene classes associated with plant defenses against abiotic and biotic stress may be co-regulated. Implications of the effects of PGPR on the induction of plant defense pathways are discussed.     

Belowground organism activities affect plant aboveground phenotype, inducing plant tolerance to parasites

Soil fauna activities are probably more important than currently acknowledged in determining individual plant response to stresses and overall plant diversity. Here we demonstrate that the positive effect of earthworms on rice could be the result of a systemic effect on plant physiology. Moreover, this effect could improve tolerance to stressors such as parasitic nematodes. In a controlled experiment, an 82% decrease in the production of infested plants was suppressed when earthworms were present. Earthworms had no direct effect on nematode population size. In their presence, however, root biomass was not affected by nematodes and the expected inhibition of photosynthesis was suppressed. In the leaves, the expression of three stress‐responsive genes (coding for lipoxygenase, phospholipase D and cysteine protease) was modulated by the presence of belowground invertebrate activities. We document conflicting systemic effects of parasitic nematodes and beneficial earthworms, although we cannot precisely identify the mechanism involved. These results reveal the importance of non‐trophic belowground/aboveground interactions for plant health and response to stresses.     

杜仲叶片干旱胁迫响应相关差异蛋白的筛选与鉴定

为研究干旱胁迫下杜仲幼苗生理生化及分子响应机制,利用盆栽试验,通过持续（3、6、9、12、15 d）干旱胁迫处理和复水处理,研究杜仲幼苗的生理响应特性。同时,通过研究对照与处理15 d后的杜仲幼苗差异蛋白质组,分析杜仲幼苗对干旱胁迫的分子响应机制。结果表明,随着干旱处理时间的延长,杜仲叶片的水分饱和亏逐渐增加;光合速率、蒸腾速率、胞间二氧化碳浓度、气孔导度均逐渐减小;SOD、POD、CAT活性呈先上升后降低的趋势;丙二醛含量则呈现先上升,然后下降,最后又上升的变化特点;脯氨酸和可溶性糖含量的变化趋势与SOD等活性变化一致,前期上升,后期下降。在复水后,杜仲叶片的所有指标均有所恢复,但未达到干旱处理之前的水平。表明干旱胁迫影响了杜仲叶片的正常生长代谢。通过对干旱处理15 d后杜仲叶片总蛋白进行双向电泳分离和MALDI-TOF-TOF生物质谱鉴定,成功鉴定出36个差异表达蛋白,其中22个上调表达,14个下调表达。对36个差异蛋白进行功能分析发现,这些差异蛋白主要涉及信号传导、光合作用、碳代谢、能量代谢、次级代谢物合成、抗氧化保护酶、氨基酸代谢和蛋白质代谢。推测杜仲为适应干旱胁迫,首先是感应干旱胁迫信号,并传导至细胞内,影响杜仲叶片中光合作用、次级代谢物合成和蛋白质的生物合成;同时,通过过氧化物保护酶的作用,将过多活性氧加以清除;另一方面,则是通过增强糖酵解,磷酸戊糖途径,产生能量供杜仲正常生长所需。从生理机制来看,杜仲叶片同过增加胞内脯氨酸、可溶性糖含量,降低胞内渗透势,减少叶片中水分损失,与氨基酸合成和糖代谢相关蛋白的表达量上升的结果一致。