Species In Plant Tissues Research Articles

Improved efficiency of Sedum lineare (Crassulaceae) in remediation of arsenic-contaminated soil by phosphate-dissolving strain P-1 in association with phosphate rock.

The selection of appropriate plants and growth strategies is a key factor in improving the efficiency and universal applicability of phytoremediation. Sedum lineare grows rapidly and tolerates multiple adversities. The effects of inoculation of Acinetobacter sp. phosphate solubilizing bacteria P-1 and application of phosphate rock (PR) as additives on the remediation efficiency of As-contaminated soil by S. lineare were investigated. Compared with the control, both the single treatment and the combination of inoculation with strain P-1 and application of PR improved the biomass by 30.7-395.5%, chlorophyll content by 48.1-134.8%, total protein content by 12.5-92.4% and total As accumulation by 45.1-177.5%, and reduced the As-induced oxidative damage. Inoculation with strain P-1 increased the activities of superoxide dismutases and catalases of S. lineare under As stress, decreased the accumulation of reactive oxygen species in plant tissues and promoted the accumulation of As in roots. In contrast, simultaneous application of PR decreased As concentration in S. lineare tissues, attenuated As-induced lipid peroxidation and improved As transport to shoots. In addition, the combined application showed the best performance in improving resistance and biomass, which significantly increased root length by 149.1%, shoot length by 33%, fresh weight by 395.5% and total arsenic accumulation by 159.2%, but decreased the malondialdehyde content by 89.1%. Our results indicate that the combined application of strain P-1 and PR with S. lineare is a promising bioremediation strategy to accelerate phytoremediation of As-contaminated soils.

Visualizing vinca alkaloids in the petal of Catharanthus roseus using functionalized titanium oxide nanowire substrate for surface-assisted laser desorption/ionization imaging mass spectrometry.

Imaging mass spectrometry (IMS) is a powerful technique that enables analysis of various molecular species at a high spatial resolution with low detection limits. In contrast to the matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) approach, surface-assisted laser desorption/ionization (SALDI) can be more effective in the detection of small molecules due to the absence of interfering background signals in low m/z ranges. We developed a functionalized TiO2 nanowire as a solid substrate for IMS of low-molecular-weight species in plant tissues. We prepared TiO2 nanowires using an inexpensive modified hydrothermal process and subsequently functionalized them chemically with various silane analogs to overcome the problem of superhydrophilicity of the substrate. Chemical modification changed the selectivity of imprinting of samples deposited on the substrate surface and thus improved the detection limits. The substrate was applied to image distribution of the metabolites in very fragile specimens such as the petal of Catharanthus roseus. We observed that the metabolites are distributed heterogeneously in the petal, which is consistent with previous results reported for the C. roseus plant leaf and stem. The intermediates corresponding to the biosynthesis pathway of some vinca alkaloids were clearly shown in the petal. We also performed profiling of petals from five different cultivars of C. roseus plant. We verified the semi-quantitative capabilities of the imprinting/imaging approach by comparing results using the LC-MS analysis of the plant extracts. This suggested that the functionalized TiO2 nanowire substrate-based SALDI is a powerful technique complementary to MALDI-MS.

Techniques for the Measurement of Molecular Species of Acyl-CoA in Plants and Microalgae.

The acyl-CoA pool is pivotal in cellular metabolism. The ability to provide reliable estimates of acyl-CoA abundance and distribution between molecular species in plant tissues and microalgae is essential to our understanding of lipid metabolism and acyl exchange. Acyl-CoAs are typically found in low abundance and require specific methods for extraction, separation and detection. Here we describe methods for acyl-CoA extraction and measurement in plant tissues and microalgae, with a focus on liquid chromatography hyphenated to detection techniques including ultraviolet (UV), fluorescence and mass spectrometry (MS). We address the resolution of isobaric species and the selection of columns needed to achieve this, including the analysis of branched chain acyl-CoA thioesters. For MS analyses, we describe diagnostic ions for the identification of acyl-CoA species and how these can be used for both discovery of new species (data dependent acquisition) and routine quantitation (triple quadrupole MS with multiple reaction monitoring).

Separation of selenium species in plant tissues by high performance liquid chromatography-ultraviolet treatment-hydride generation atomic fluorescence spectrometry using various mobile phases

Anion-exchange chromatography (Hamilton, PRP-X100) with hydride-generation atomic fluorescence spectrometry (HG-AFS) is commonly used for selenium (Se) speciation analysis in environmental and biological samples. However, retentions of Se species are often different with different mobile phases. To address it, this study systematically investigated mobile phases based on ammonium salts to obtain good resolution of Se species. Various mobile phases, including NH4H2PO4, NH4Ac, NH4NO3 and (NH4)2HPO4, were tested. The best result was obtained with a mobile phase containing 60 mmol L −1 (NH4)2HPO4 at pH 6.0, where the separation of Se species, including selenite [Se(IV)], selenate [Se(VI)], selenocystine (SeCys) and selenomethionine (SeMet), was achieved within 10 min with reasonable resolution. In addition, the recoveries of SeCys, Se (IV), SeMet and Se (VI) in the Se-enriched samples were 95.72 ± 1.60%, 106.89 ± 2.20%, 93.28 ± 2.82% and 91.38 ± 1.27%, respectively. Finally, the proposed method was validated for the determination of Se species in Nicotiana tabacum tissues.

Volatile Metabolic Markers for Monitoring Pectobacterium carotovorum subsp. carotovorum Using Headspace Solid-Phase Microextraction Coupled with Gas Chromatography-Mass Spectrometry.

Identifying the extracellular metabolites of microorganisms in fresh vegetables is industrially useful for assessing the quality of processed foods. Pectobacterium carotovorum subsp. carotovorum (PCC) is a plant pathogenic bacterium that causes soft rot disease in cabbages. This microbial species in plant tissues can emit specific volatile molecules with odors that are characteristic of the host cell tissues and PCC species. In this study, we used headspace solid-phase microextraction followed by gas chromatography coupled with mass spectrometry (HS-SPME-GC-MS) to identify volatile compounds (VCs) in PCC-inoculated cabbage at different storage temperatures. HS-SPME-GC-MS allowed for recognition of extracellular metabolites in PCC-infected cabbages by identifying specific volatile metabolic markers. We identified 4-ethyl-5-methylthiazole and 3-butenyl isothiocyanate as markers of fresh cabbages, whereas 2,3-butanediol and ethyl acetate were identified as markers of soft rot in PCC-infected cabbages. These analytical results demonstrate a suitable approach for establishing non-destructive plant pathogen-diagnosis techniques as alternatives to standard methods, within the framework of developing rapid and efficient analytical techniques for monitoring plant-borne bacterial pathogens. Moreover, our techniques could have promising applications in managing the freshness and quality control of cabbages.

Bitkilerde Aktif Oksijen Türleri ve Oksidatif Stres

Aerobik organizmalar için oksijen vazgeçilmez bir moleküldür. Biyotik ve abiyotik stres faktörleri altında bitkilerde elektron taşınımı ile ilgili reaksiyonlar aktif oksijen türlerinin oluşum hızını artırır. Bu reaksiyonlarda elektronlar stres faktörlerinin etkisiyle asıl hedef molekül yerine oksijene verilir. Bu şekilde başlayan zincirleme reaksiyonlar bitki dokularında süperoksit radikali, hidrojen peroksit ve hidroksil radikali gibi aktif oksijen türlerinin birikim göstermeye başlamasına yol açar. Antioksidant sistemin yeterince aktive edilememesi durumunda oldukça reaktif olan aktif oksijen türleri hücresel bileşenlere zarar vermeye başlar. Bu olay oksidatif stres olarak bilinir. Aktif oksijen türleri bitki hücrelerindeki birçok organelde oluşabilir. Kloroplastlar bitki hücrelerinde aktif oksijen türlerini oluşturma kapasitesi bakımından en aktif organellerdir. Bunun dışında mitokondriler, peroksizomlar, endoplazmik retikulum gibi organellerle apoplastik bölgede de aktif oksijen oluşumu gözlenir. Stres koşulları altında sekonder bir stres olarak ortaya çıkan oksidatif stres tarımsal verimliliği tehdit eden en önemli faktör olarak kabul edilmektedir. Bu derlemede bitki hücrelerinde aktif oksijen türlerinin oluşumuna neden olan metabolik olaylar, bu bileşiklerin kimyasal özellikleri ve oksidatif hasar oluşturma mekanizmaları tartışılmıştır.

ШЎРЛАНИШ ШАРОИТИДА ҒЎЗАНИНГ ОКСИДЛАНИШ ЖАРАЁНЛАРИГА ДАГ-1 ВА ДАГ-2 ТАБИИЙ АСОСЛИ ПРЕПАРАТЛАРИНИНГ ТАЪСИРИ

Salt stress enhances the formation of reactive oxygen species in plant tissues associated with damage to the structure of cell macromolecules, leading to disruption of cellular metabolism. The use of drugs of natural origin DAG-1 and DAG-2 can be effective in adapting cotton to the effects of salts. The activity of the pro-/antioxidant system in 7-day-old cotton seedlings, seeds of which were treated with DAG-1 and DAG-2 drugs and germinated in various concentrations of NaCl solution (100 mM, 200 mM, 300 mM) has been studied. Salinity resistance is manifested in cotton varieties treated with natural drugs DAG-1 and DAG-2, in which a high activity of the key enzyme of the antioxidant system - superoxide dismutase, low content of final product of lipid peroxidation – malondialdehyde and the accumulation of free proline amino acid with osmoprotective property have been identified.

Antioxidant enzyme activities in male and female plants of Hippophae salicifolia D. Don in different pheno-phases

Changing seasons or environmental condition of a region and various life phases of the yearly cycle of plants can cause the production of reactive oxygen species in plant tissues. The antioxidative system plays a vital role in acclimations in such stress-full conditions, either enzymes or non-enzymatic molecules. Hippophae salicifolia D. Don. is a dioecious and deciduous tree species growing in temperate to the subalpine region of Indian Himalayas in Lahul Spiti (Himachal Pradesh), Uttarakhand, Sikkim, and Arunachal Pradesh. As a dioecious species, variation in male and female was observed in many aspects in both sexual-morph in a range of studies. A hypothesis was made in this study, that male and female plant of H. salicifolia has a different antioxidant potential for quenching the reactive oxygen species in the various growing season of the year, and the antioxidant enzyme activities of male and female also vary with pheno-phases. For this purpose, 10-year-old male and female plants were selected, and leaves and buds were collected from them according to the growing season. Enzymatic extraction was carried out according to the standardized method and enzyme assays were carried out for superoxide dismutase (SOD) and peroxidase (POD). Results showed the variation in SOD and POD enzyme activities in leaves and buds of male and female plants of H. salicifolia in different pheno-phases. Female leaves showed highest enzymatic antioxidant activities in the fruit maturation period (September) and lowest during leaf senescence period (November), whereas male leaves showed highest SOD activity in September but highest POD activity in July. Buds showed higher SOD activity, but lower POD activity than the leaves and differences in activity was not significant in dormant buds at gender basis, active buds showed lower SOD activity but higher POD activity in both male and female.

Dissecting the Physiological Function of Plant Glyoxalase I and Glyoxalase I-Like Proteins.

The Arabidopsis genome annotation include 11 glyoxalase I (GLXI) genes, all encoding for protein members of the vicinal oxygen chelate (VOC) superfamily. The biochemical properties and physiological importance of three Arabidopsis GLXI proteins in the detoxification of reactive carbonyl species has been recently described. Analyses of phylogenetic relationships and conserved GLXI binding sites indicate that the other eight GLXI genes (GLXI-like) do not encode for proteins with GLXI activity. In this perspective article we analyse the structural features of GLXI and GLXI-like proteins, and explore splice forms and transcript abundance under abiotic stress conditions. Finally, we discuss future directions of research on this topic with respect to the substrate identification of GLXI and GLXI-like proteins and the need of reliable quantitative measurements of reactive carbonyl species in plant tissues.

Ethylenediamine disuccinic acid enhanced phytoextraction of nickel from contaminated soils using Coronopus didymus (L.) Sm.

In a screenhouse, the applicability of biodegradable chelant ethylenediamine disuccinic acid (EDDS) to enhance Ni-phytoextraction by Coronopus didymus was tested for the first time. This study assayed the hypothesis based upon the role of EDDS on physiological and biochemical alterations and ameliorating phytoextraction capacity of C. didymus under nickel (Ni) stress. Pot experiments were conducted for 6 weeks and C. didymus plants were cultivated in soil artificially contaminated with 30, 50, and 70 mg kg−1 Ni treatments. Soil was amended with EDDS (2 mmol kg−1). Plants were harvested, 1 week after EDDS application. At 70 mg kg−1 Ni level, EDDS application dramatically enhanced the root and shoot Ni concentration from 665 and 644 to 1339 and 1338 mg kg−1, respectively. Combination of Ni + EDDS induced alterations in biochemical parameters of plants. EDDS addition posed pessimistic effects on growth, biomass, photosynthetic activity and protein content of the plants. Besides, application of EDDS stimulated the generation of superoxide anion, H2O2 content and MDA level. However, EDDS assisted mount in antioxidant activities (superoxide dismutase, catalase and glutathione peroxidase) considerably neutralised the toxicity induced by reactive oxygen species in plant tissues. The results revealed EDDS efficacy to ameliorate the performance of antioxidant enzymes and improved Ni translocation in plant tissues, thus strongly marked its affinity to be used together with C. didymus for Ni-phytoextraction.

Mercury species accumulation and distribution in Typha domingensis under real field conditions (Almadén, Spain).

Monomethylmercury (MeHg) is one of the most toxic and the most commonly occurring organomercury compound and the wetlands are one of the main areas of generation of this Hg form. Concretely, it is in the macrophyte root system where better conditions are given for its generation. However, the knowledge of absorption and subsequent distribution of mercury (Hg) and monomethylmercury in aquatic plants is still limited. Mercury mining district such as Almadén (Ciudad Real, Spain) is a natural laboratory where different rivers flow and the species Typha domingensis Pers. is a common macrophyte which grows in their riverbanks. The aim of the present work is to apply a recently developed method specially designed to analyze Hg species in plant tissues to the different fractions of T. domingensis under real field conditions and to study the accumulation and distribution of Hg species (inorganic Hg and MeHg) within the plant. The results proved that whatever Hg species has preference to be accumulated in the belowground fractions and demonstrated a high efficiency in the accumulation of MeHg.

Contrasting effects of engineered carbon nanotubes on plants: a review.

Rapid surge of interest for carbon nanotube (CNT) in the last decade has made it an imperative member of nanomaterial family. Because of the distinctive physicochemical properties, CNTs are widely used in a number of scientific applications including plant sciences. This review mainly describes the role of CNT in plant sciences. Contradictory effects of CNT on plants physiology are reported. CNT can act as plant growth inducer causing enhanced plant dry biomass and root/shoot lengths. At the same time, CNT can cause negative effects on plants by forming reactive oxygen species in plant tissues, consequently leading to cell death. Enhanced seed germination with CNT is related to the water uptake process. CNT can be positioned as micro-tubes inside the plant body to enhance the water uptake efficiency. Due to its ability to act as a slow-release fertilizer and plant growth promoter, CNT is transpiring as a novel nano-carbon fertilizer in the field of agricultural sciences. On the other hand, accumulation of CNT in soil can cause deleterious effects on soil microbial diversity, composition and population. It can further modify the balance between plant-toxic metals in soil, thereby enhancing the translocation of heavy metal(loids) into the plant system. The research gaps that need careful attention have been identified in this review.

Effect of low temperature on flavonoids, oxygen radical absorbance capacity values and major components of winter sweet spinach (Spinacia oleracea L.)

Winter sweet treatment (WST) has been established for cultivating high-quality leafy vegetables during the winter. Although it is known that chilling stress during cold acclimation induces oxidative damage by reactive oxygen species in plant tissues, knowledge about changes in antioxidant activity and compounds during WST in spinach is superficial. We investigated changes in flavonoids, total ascorbic acid, carotenoids and hydrophilic oxygen radical absorbance capacity (H-ORAC) along with components in three spinach varieties during low-temperature treatment by exposure to cold air in winter. The H-ORAC values increased substantially together with total flavonoids and total ascorbic acid concentration. In addition, WST increased mono- and diglucosylated flavonoid derivatives with an ortho-dihydroxy (catechol) structure of lower molecular weight in spinach. These results suggest that WST contributes to the prevention of low-temperature-induced oxidative damage by increasing the level of antioxidant compounds, thereby improving antioxidant activity. Although sucrose concentrations were increased by WST, nitrate and oxalate concentrations did not increase in any variety. WST can contribute to the increase in antioxidant compounds such as flavonoids and ascorbic acids, antioxidant activity and sucrose without increasing in nitrate and oxalate of spinach.

Toxicity of ZnO engineered nanoparticles and evaluation of their effect on growth, metabolism and tissue specific accumulation in Brassica juncea

Metal nanoparticles have many potential technological applications; it hassled the issue regarding unidentified consequences of their release into the environment. Present study deals with the effects of zinc oxide (ZnO) engineered nanoparticles (ENPs) on plant growth, bioaccumulation and antioxidative enzyme activity in Brassica juncea. The seed was germinated under hydroponic condition with a varying concentration of ZnO ENPs (0, 200, 500, 1000, 1500mg/l) for 96h. Significant decrease in plant biomass was recorded with gradual increase in proline content and lipid peroxidation upto a concentration of 1000mg/l. Estimation of the antioxidant enzyme [catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR) and superoxide dismutase (SOD)] activities in different plant tissues was done. Further, bioaccumulation of ZnO ENPs was also recorded. ENPs caused a significant effect due to their accumulation along with the generation of reactive oxygen species in plant tissues, thus signifying its hazardous effect on B. juncea.

Comparative analysis of the biodiversity of fungal endophytes in insect-induced galls and surrounding foliar tissue

Insect-induced galls are abnormal plant growths that can provide food and shelter to their inhabitants, resulting in stressed plant tissue that may alter the conditions for the colonization or proliferation of endophytic fungi. We investigated the effect gall formation has on fungal endophyte communities and diversity. Using three closely-related gall-forming aphid species that specialize on poplars, we characterized fungal endophyte diversity in galls and surrounding petiole and leaf lamina tissue. A total of 516 fungal endophyte samples were isolated from 272 tissue samples (32 leaves, 31 petioles, and 209 galls), resulting in 23 distinct morphotypes. Despite sharing a common host plant and often forming spatially contiguous galls, the endophyte profiles within the galls of each aphid species were distinct, not only from the galls of the other species, but also from surrounding plant tissue. These results suggest that insect galls can affect the composition of fungal endophyte species in plant tissues, by altering either the colonization or proliferation of their endophytic mycobiota. Likewise, fungal endophytes may be important in the ecology and evolution of insect galls.

Evaluation of sample preparation procedures and krypton as an interference standard probe for arsenic speciation by HPLC-ICP-QMS

Different conditions of extraction using water, a methanol–water mixture and nitric acid solutions were evaluated for speciation of As(III), As(V), DMA and MMA in plant samples that previously received As(V) after being sown and emergence was investigated. Microwave-assisted extraction (MAE) using diluted nitric acid solutions was also performed for arsenic extraction from chicken feed samples. The separation and determination of arsenic species were performed using HPLC-ICP-MS. The interference standard method (IFS) using 83Kr+ as the IFS probe was employed to minimize spectral interferences caused by polyatomic species, such as 40Ar35Cl+. The extraction procedures tested presented adequate extraction efficiencies (90%), and the four arsenic species evaluated were found in plant samples. Extractions with diluted nitric acid solution at 90 °C were the most efficient strategy, with quantitative recoveries for all four As species in plant tissues. On the other hand, the methanol–water mixture was the solvent with the lowest extraction efficiency (50–60%). For chicken feed samples, MAE at 100 °C for 30 min resulted in an extraction efficiency of 97% and only As(V) was found, without any species interconversion. The IFS method contributed to improving precision and limits of detection and quantification for all tested extraction procedures. Significant improvements on accuracy were obtained by applying the IFS method and recoveries between 77 and 94%, and 82 and 93% were obtained for plant extracts and chicken feed samples, respectively.

Spatial Mapping of Lipids at Cellular Resolution in Embryos of Cotton

Advances in mass spectrometry (MS) have made comprehensive lipidomics analysis of complex tissues relatively commonplace. These compositional analyses, although able to resolve hundreds of molecular species of lipids in single extracts, lose the original cellular context from which these lipids are derived. Recently, high-resolution MS of individual lipid droplets from seed tissues indicated organelle-to-organelle variation in lipid composition, suggesting that heterogeneity of lipid distributions at the cellular level may be prevalent. Here, we employed matrix-assisted laser desorption/ionization-MS imaging (MALDI-MSI) approaches to visualize lipid species directly in seed tissues of upland cotton (Gossypium hirsutum). MS imaging of cryosections of mature cotton embryos revealed a distinct, heterogeneous distribution of molecular species of triacylglycerols and phosphatidylcholines, the major storage and membrane lipid classes in cotton embryos. Other lipids were imaged, including phosphatidylethanolamines, phosphatidic acids, sterols, and gossypol, indicating the broad range of metabolites and applications for this chemical visualization approach. We conclude that comprehensive lipidomics images generated by MALDI-MSI report accurate, relative amounts of lipid species in plant tissues and reveal previously unseen differences in spatial distributions providing for a new level of understanding in cellular biochemistry.

Species-specific PCR–DGGE markers to distinguish Pyrenophora species associated to cereal seeds

Pyrenophora species, toxigenic cereal pathogens, and causal agents of leaf and kernel diseases, bring about economic and food safety concerns. Traditionally, Pyrenophora taxa have been identified microscopically after a period of incubation on culture media. In this study, a simple nested PCR–denaturing gel electrophoresis (DGGE) method was developed to detect, differentiate and identify six Pyrenophora species in plant tissues. A primer, specific to Pyrenophora species and able to amplify a fragment of the ribosomal RNA (rRNA), following first round amplification with universal ITS primers, was designed by reviewing Pyrenophora ribosomal DNA sequences deposited in GenBank. The specificity of the primer was assessed by submitting its sequence to the GenBank Basic Local Alignment Search Tool (BLAST) algorithm, and was also tested with DNA extracted from several ascomycetous, basidiomycetous, and zygomycetous taxa. No PCR product was obtained from non- Pyrenophora species. PCR amplification of DNA extracted from pure cultures of the different Pyrenophora species generated amplicons of an approximate 350 bp. DGGE effectively separated between all six Pyrenophora amplicons. Subsequently, amplicons of known Pyrenophora species were used as molecular markers when Pyrenophora infected wheat seed was analyzed by PCR–DGGE. The molecular-based approach described herein can be used to identify different Pyrenophora species directly from infected plant material.

Oxidative Stress and Antioxidants in Tomato (Solanum lycopersicum) Plants Subjected to Boron Toxicity

Boron (B) toxicity triggers the formation of reactive oxygen species in plant tissues. However, there is still a lack of knowledge as to how B toxicity affects the plant antioxidant defence system. It has been suggested that ascorbate could be important against B stress, although existing information is limited in this respect. The objective of this study was to analyse how ascorbate and some other components of the antioxidant network respond to B toxicity. Two tomato (Solanum lycopersicum) cultivars ('Kosaco' and 'Josefina') were subjected to 0.05 (control), 0.5 and 2 mm B. The following were studied in leaves: dry weight; relative leaf growth rate; total and free B; H(2)O(2); malondialdehyde; ascorbate; glutathione; sugars; total non-enzymatic antioxidant activity, and the activity of superoxide dismutase, catalase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase, ascorbate oxidase and l-galactose dehydrogenase. The B-toxicity treatments diminished growth and boosted the amount of B, malondialdehyde and H(2)O(2) in the leaves of the two cultivars, these trends being more pronounced in 'Josefina' than in 'Kosaco'. B toxicity increased ascorbate concentration in both cultivars and increased glutathione only in 'Kosaco'. Activities of antioxidant- and ascorbate-metabolizing enzymes were also induced. High B concentration in the culture medium provokes oxidative damage in tomato leaves and induces a general increase in antioxidant enzyme activity. In particular, B toxicity increased ascorbate pool size. It also increased the activity of l-galactose dehydrogenase, an enzyme involved in ascorbate biosynthesis, and the activity of enzymes of the Halliwell-Asada cycle. This work therefore provides a starting point towards a better understanding of the role of ascorbate in the plant response against B stress.

Isolation and Characterization of Four Ascorbate Peroxidase cDNAs Responsive to Water Deficit in Cowpea Leaves

Abiotic stresses stimulate formation of active oxygen species in plant tissues. Among antioxidant mechanisms, H2O2 detoxication by ascorbate peroxidases (APX) plays an important role. Several APX isoforms exist in plant cells, and they have rarely been studied separately. The aim of this work was to study changes in cytosolic, peroxisomal, stromatic and thylakoid APX gene expression in response to progressive drought, rapid desiccation and application of exogenous abscisic acid in the leaves of cowpea (Vigna unguiculata) plants. Two cowpea (V. unguiculata) cultivars, 'EPACE-1' which is drought-tolerant and '1183'which is drought-sensitive, were submitted to drought stress by withholding irrigation. Detached leaves were air-dried or treated with exogenous abscisic acid. APX cDNAs were isolated by PCR and cloned in plasmid vectors. Changes in gene expression were studied using reverse-transcription PCR. Four new V. unguiculata cDNAs encoding putative cytosolic, peroxisomal and chloroplastic (stromatic and thylakoidal) APX were isolated and characterized. In response to the different treatments, higher increases in steady-state transcript levels of the cytoplasmic and peroxisomal APX genes were observed in '1183' compared with 'EPACE-1'. On the other hand, the expression of the chloroplastic APX genes was stimulated earlier in the tolerant cultivar when submitted to progressive drought. Water deficit induced differences in transcript accumulation of APX genes between the two cultivars that were related to their respective tolerance to drought. Chloroplastic APX genes responded early to progressive water deficit in the tolerant plant, suggesting a capacity to efficiently detoxify active oxygen species at their production site. The more sensitive '1183' was also able to respond to drought by activating its whole set of APX genes.