Nanoselenium transformation and inhibition of cadmium accumulation by regulating the lignin biosynthetic pathway and plant hormone signal transduction in pepper plants.

Selenium (Se) can promote the growth and resistance of agricultural crops as fertilizers, while the role of nano-selenium (nano-Se) against Cd remains unclear in pepper plants (Capsicum annuum L.). Biofortification with nano-Se observably restored Cd stress by decreasing the level of Cd in plant tissues and boosting the accumulation in biomass. The Se compounds transformed by nano-Se were primarily in the form of SeMet and MeSeCys in pepper tissues. Differential metabolites and the genes of plant signal transduction and lignin biosynthesis were measured by employing transcriptomics and determining target metabolites. The number of lignin-related genes (PAL, CAD, 4CL, and COMT) and contents of metabolites (sinapyl alcohol, phenylalanine, p-coumaryl alcohol, caffeyl alcohol, and coniferaldehyde) were remarkably enhanced by treatment with Cd1Se0.2, thus, maintaining the integrity of cell walls in the roots. It also enhanced signal transduction by plant hormones and responsive resistance by inducing the biosynthesis of genes (BZR1, LOX3, and NCDE1) and metabolites (brassinolide, abscisic acid, and jasmonic acid) in the roots and leaves. In general, this study can enable a better understanding of the protective mechanism of nano-Se in improving the capacity of plants to resist environmental stress.

Identification of Compounds with Potential Therapeutic Uses from Sweet Pepper (Capsicum annuum L.) Fruits and Their Modulation by Nitric Oxide (NO).

Plant species are precursors of a wide variety of secondary metabolites that, besides being useful for themselves, can also be used by humans for their consumption and economic benefit. Pepper (Capsicum annuum L.) fruit is not only a common food and spice source, it also stands out for containing high amounts of antioxidants (such as vitamins C and A), polyphenols and capsaicinoids. Particular attention has been paid to capsaicin, whose anti-inflammatory, antiproliferative and analgesic activities have been reported in the literature. Due to the potential interest in pepper metabolites for human use, in this project, we carried out an investigation to identify new bioactive compounds of this crop. To achieve this, we applied a metabolomic approach, using an HPLC (high-performance liquid chromatography) separative technique coupled to metabolite identification by high resolution mass spectrometry (HRMS). After chromatographic analysis and data processing against metabolic databases, 12 differential bioactive compounds were identified in sweet pepper fruits, including quercetin and its derivatives, L-tryptophan, phytosphingosin, FAD, gingerglycolipid A, tetrahydropentoxylin, blumenol C glucoside, colnelenic acid and capsoside A. The abundance of these metabolites varied depending on the ripening stage of the fruits, either immature green or ripe red. We also studied the variation of these 12 metabolites upon treatment with exogenous nitric oxide (NO), a free radical gas involved in a good number of physiological processes in higher plants such as germination, growth, flowering, senescence, and fruit ripening, among others. Overall, it was found that the content of the analyzed metabolites depended on the ripening stage and on the presence of NO. The metabolic pattern followed by quercetin and its derivatives, as a consequence of the ripening stage and NO treatment, was also corroborated by transcriptomic analysis of genes involved in the synthesis of these compounds. This opens new research perspectives on the pepper fruit's bioactive compounds with nutraceutical potentiality, where biotechnological strategies can be applied for optimizing the level of these beneficial compounds.

Salicylic acid-induced hydrogen sulphide improves lead stress tolerance in pepper plants by upraising the ascorbate-glutathione cycle.

The contribution of hydrogen sulphide (H2 S) to salicylic acid (SA) induced lead (Pb) stress tolerance modulated by the ascorbate-glutathione (AsA-GSH) cycle was examined in pepper (Capsicum annuum L.) plants. One week after germination, pepper seedlings were sprayed with 0.5 mM SA once a day for a week. Thereafter, seedlings were grown under control (no Pb) or Pb stress (Pb-S treatment consisting of 0.1 mM PbCl2 ) for a further 2 weeks. Lead stress reduced plant growth and leaf water status as well as the activities of dehydroascorbate reductase and monodehydroascorbate reductase. However, lead stress elevated leaf Pb, the proline contents, oxidative stress, activities of glutathione reductase and ascorbate peroxidase, as well as the endogenous H2 S content. Supplements of SA resulted in improvements in growth parameters, biomass, leaf water status and AsA-GSH cycle-related enzyme activities, as well as increasing the H2 S content. The positive effect of SA was further enhanced when sodium hydrosulphide was added. However, 0.1 mM hypotaurine (HT) treatment reversed the beneficial effect of SA by reducing the plant H2 S content. Application of NaHS in combination with SA + HT suppressed the adverse effect of HT mainly by restoring the plant H2 S content, suggesting that higher H2 S content, induced by exogenous SA supply, resulted in elevated regulation of the AsA-GSH cycle.

Nanoselenium Foliar Applications Enhance the Nutrient Quality of Pepper by Activating the Capsaicinoid Synthetic Pathway.

Increasing the crop quality through enhancement of plant health is a challenging task. In this study, nanoselenium (nano-Se) was sprayed on pepper leaves, and the pepper components were compared to those of selenite. It was found that nano-Se (20 mg/L) resulted in a greater performance of plant health. It increased the chlorophyll and soluble sugar levels, which could activate phenylpropane and branched-chain fatty acid pathways, as well as AT3-related enzymes and gene expressions. These led to an enhancement for the synthesis of capsaicinoids, flavonoids, and total phenols. The nano-Se treatment also significantly promoted the expression of phyto-hormones synthesis genes, and consequently increased jasmonic, abscisic, and salicylic acid levels. Proline pathway-related compounds were increased, which could decrease the malondialdehyde and hydroxyl radical levels in crops. This study shows that nano-Se activated capsaicinoid pathways by enhancing photosynthesis and raising soluble sugar levels. The capsaicinoid contents in peppers were then increased, which consequently promoted the accumulation of secondary metabolites and antioxidants.

Exogenously supplied silicon (Si) improves cadmium tolerance in pepper (Capsicum annuum L.) by up-regulating the synthesis of nitric oxide and hydrogen sulfide.

The current research was aimed to observe the interactive role of silicon-generated hydrogen sulfide (H2S) and nitric oxide (NO) on tolerance of pepper (Capsicum annum L.) plants to cadmium (Cd). Thus, the pepper plants were subjected to control (no Cd) or cadmium stress with and without Si supplementation. Significant decreases were found in plant dry weights, water potential, PSII maximum efficiency, glutathione (GSH), total chlorophyll, relative water content, Ca2+ and K+ concentrations and ascorbate, but there was a significant increase in H2O2, MDA, electron leakage (EL), proline, key antioxidant enzymes' activities, and endogenous Cd, NO and H2S in the Cd-stressed plants. Silicon enhanced Cd tolerance of the pepper plants by lowering the leaf Cd concentration, oxidative stress, enhancing the antioxidant defence system, leaf Si content, photosynthetic traits and plant growth as well as the contents of NO, proline and H2S. Furthermore, foliar-applied NO scavenger, cPTIO, and that of H2S, hypotaurine (HT), significantly decreased the levels of H2S alone, but cPTIO effectively reduced the concentrations of NO and H2S accumulated by Si in the Cd-stressed plants. The positive effect of Si was eliminated by cPTIO, but not by HT, suggesting that both molecules were involved in Si-induced improvement in Cd tolerance of the pepper plants.

Inhibitory Activity of Flavonoids, Chrysoeriol and Luteolin-7-O-Glucopyranoside, on Soluble Epoxide Hydrolase from Capsicum chinense.

: Three flavonoids derived from the leaves of Capsicum chinense Jacq. were identified as chrysoeriol (1), luteolin-7-O-glucopyranoside (2), and isorhamnetin-7-O-glucopyranoside (3). They had IC50 values of 11.6±2.9, 14.4±1.5, and 42.7±3.5 µg/mL against soluble epoxide hydrolase (sEH), respectively. The three inhibitors (1-3) were found to non-competitively bind into the allosteric site of the enzyme with Ki values of 10.5±3.2, 11.9 ±2.8 and 38.0±4.1 µg/mL, respectively. The potential inhibitors 1 and 2 were located at the left edge ofa U-tube shape that contained the enzyme active site. Additionally, we observed changes in several factors involved in the binding of these complexes under 300 K and 1 bar. Finally, it was confirmed that each inhibitor, 1 and 2, could be complexed with sEH by the "induced fit" and "lock-and-key" models.

Plant Defense System Activated in Chili Plants by Using Extracts from Eucalyptus citriodora.

Capsicum annuum L. is infected by Fusarium Wilt and causes significant yield losses in Pakistan. Biological control is an excellent and environment friendly way. Presently, the biocontrol assays were conducted in pot trials using methanolic leaf extract of Eucalyptus citriodora L. where spray of extract prior to infection provided better protection from pathogen with maximum disease control. Further, Native page electrophoresis was performed to find out difference in expression profile of enzyme which revealed that control and T2 (Plant sprayed with Eucalyptus extract) did not exhibit any difference in their isozyme profile signifying no extra load of biological control measure on plant for the production of defense elements until the pathogen arrived. While in case of T3 （Protective treatment） and T4 (Curative treatment) extra isozyme (PO1) was observed in T4 only, PPO1 and PPO5, and PAL 2 and PAL 3 were comprised in higher quantities in T3 and T4 over control exposing the expression of plant metabolism under pathogen attack. The study concludes that the organic extract of E. citriodora have the potential to restrain the disastrous effects of pathogenic fungi. It will lead to the different aspect of biocontrol to suppress the plant pathogenic fungi in a broad spectrum.

Leaf-induced callus formation in two cultivars: hot pepper 'CM334' and bell pepper 'Dempsey'.

Pepper (Capsicum annuum), one of the most economically important vegetables of the Solanaceae family, is cultivated worldwide. To apply versatile genome-editing tools to a pepper genome for precise molecular breeding, an in vitro regeneration protocol is indispensable and callus formation is an essential step in the regeneration of pepper. Here, we show that calli were successfully induced from young leaves (3-4 cm) of pepper plants, the hot pepper C. annum 'CM334' ('CM334') and bell pepper C. annum 'Dempsey' ('Dempsey'), grown on soil for less than 7 weeks. The excised leaf segments of 'CM334' produced white calli in B5 medium containing 3% sucrose (3S), 2 mg/L 6-benzylaminopurine (2BAP), and 1 mg/L α-naphthalene acetic acid (1NAA). The calli were able to proliferate in B5 3S 2BAP medium supplemented with 2-morpholinoethanesulphonic acid (MES) and 1.5 mg/L NAA (1.5NAA). The excised leaf segments of 'Dempsey' produced light-yellow and friable calli in MS medium supplemented with B5 vitamins (MSB5), 3S and 1 mg/L 2,4-dichlorophenoxyacetic acid (1 2,4D), and the calli were also maintained in the same medium. Our findings establish the conditions for leaf-derived callus formation, which is the basis for regeneration of whole plants for two different pepper cultivars, for obtaining stable protoplasts, and eventually for applying genome-editing tools to improve the quality of peppers.

Improving oxidative damage, photosynthesis traits, growth and flower dropping of pepper under high temperature stress by selenium.

Pepper is mostly produced in greenhouses and fields in spring up to the end of summer. The reproductive stage coincides with high temperature of summer, which causes flowers to drop, leading to reduction in the yield, Se as a beneficial element can improved some stress indices. Control randomized design experiment was conducted to investigate the effect(s) of Se on heat stresses of pepper in control environment. Se in three concentrations of SeCl2 (4 (Se1), 6 (Se2) and 8 (Se3) mg L-1) was used at 35 ± 2 °C for 4 h a day, matching the high afternoon temperature. Growth, photosynthesis traits (Photosynthesis rate, transpiration and stomatal conductance), flower dropping and antioxidant changes were all measured. Results showed that Se1 decreased deleterious effects of heat stresses on vegetative traits (fresh and dry weight of fruit). Including dry weight of shoot, fresh and dry weight of root, and reproductive growth, such as Fresh weight and dry weight of fruit, flowers and fruit number. Photosynthesis rate, fruit antioxidant and phenol improved with the application of Se to heat stresses. POD and SOD activity increased, and MDA content decreased with Se application at the high temperature. Se also improved the P and S uptake. Generally, using 4 and 6 mg L-1 of Se could improve growth and physiological and phytochemical parameters of pepper and decrease the flower dropping at high temperature.

Integrative moringa and licorice extracts application improves Capsicum annuum fruit yield and declines its contaminant contents on a heavy metals-contaminated saline soil.

Green approaches for improving plant performance using natural supplementations are highly seeking. Following a preliminary study conducted on contaminated saline (EC = 7.75 dS m-1) and normal (EC = 1.4 dS m-1) soils, two main field trials were conducted to study the potential effects of licorice root (LRE; 0.5%) and moringa seed (MSE; 0.5%) extracts, supplemented to soil through irrigation water (SA) and/or as foliar spray (FS), on performance, physio-biochemical components, antioxidant defense system, and contaminants contents of Capsicum annuum plants grown on heavy metals-contaminated saline soil. Both extracts were applied in single treatments such as LRE-SA, MSE-SA, LRE-FS, and MSE-FS or in integrations like LRE-SA+LRE-FS, LRE-SA+MSE-FS, MSE-SA+LRE-FS, and MSE-SA+MSE-FS. The preliminary study results showed significant reductions in plant performance (growth and yield), chlorophylls content and significant increase in Cd content due to heavy metals and salt stress. However, LRE and MSE applied singly or in combinations positively modified these parameters compared to the control (SA and FS were applied with tap water). On the other hand, these parameters were not responded to LRE and/or MSE applications on the normal soil. The main studies results showed that all single or integrative treatments significantly increased plant growth and yield, leaf contents of leaf photosynthetic pigments, free proline, total soluble sugars, N, P, and K+, ratio of K+/Na+, and activities of CAT, POX, APX, SOD, and GR. In contrast, contaminants; Na+, Cd, Cu, Pb and Ni contents in plant leaves and fruits were significantly reduced on heavy metals-contaminated saline soil compared to the control. Additionally, all integrative treatments significantly exceeded all single treatments in this concern. The integrative MSE-SA+LRE-FS was the best treatment that is recommended to be used to maximize pepper plant performances and minimize plant contaminant contents on contaminated saline soils.

Holistic protocol for callus culture optimization using statistical modelling.

Plants endue a key role against illnesses caused by oxidative stress. These attributes are frequently associated with polyphenolic compounds. However, presence and concentration of secondary metabolites are affected by abiotic factors. The in vitro culture techniques can solve these drawbacks. Peppers can be a suitable alternative to obtain polyphenols. Aiming to optimise the callus culture stage from Capsicum baccatum to produce polyphenols, this work evaluated systemically the effects of the explant's origin (root, hypocotyl and cotyledon), growth hormone type (2,4-dichlorophenoxyacetic acid (2,4-D), benzylaminopurine (BAP) and a combination of 2,4-D/BAP at five-to-one ratio) and concentration (0.023-10.000 mg L-1) on callus culture efficiency parameters using a multilevel factorial design. The root explant in combination with BAP at 1.138 mg L-1 ensured the optimal values of the assessed responses; ​callus mass (225.03 mg), antioxidant activity (35.95%), total phenols (11.48 mg of GAE/g DE) and flavonoids (15.92 mg of RU/g DE) production.

Developmental landmarks during floral ontogeny of jalapeño chili pepper (Capsicum annuum L.) and the effect of gibberellin on ovary growth.

Pepper (Capsicum annuum L.) is an important horticultural crop in many regions of the world. The final shape and size of the fruit are known to be determined at a very early step of flower development. During flower development hormonal treatments using gibberellins seem to promote growth resulting in higher yield and fruit quality. However, the morphological changes that occur in the pepper flowers after these treatments are largely unknown. In the present study, we provide a description of floral development landmarks of jalapeño chili pepper (cultivar Huichol), divided in nine representative stages from its initiation until the opening of the bud. We established a correlation among external flower development and the time and pattern of reproductive organogenesis. Male and female gametogenesis progression was used to define specific landmarks during flower maturation. The pattern of expression of key genes involved in gibberellin metabolism and response was also evaluated in the nine flower stages. The proposed development framework was used to analyze the effect of gibberellin treatments in the development of the flower. We observed both an effect of the treatment in the histology of the ovary tissue and an increase in the level of expression of CaGA2ox1 and CaGID1b genes. The developmental stages we defined for this species are very useful to analyze the molecular and morphological changes after hormonal treatments.

Synergistic effect of silver nitrate and coconut water on shoot differentiation and plant regeneration from cultured cotyledons of Capsicum annuum L.

Chili pepper (Capsicum annuum L.) ranks among the most important vegetable crop belonging to the family Solanaceae that is consumed both as vegetable and spice throughout the world. C. annuum, as crop, in order to meet the target yield, demands improved variety that could overcome environmental challenges viz., biotic and abiotic stress. Cultivar improvement essentially requires an efficient in vitro regeneration protocol. In the present study, we investigated the influence of silver nitrate (AgNO3) and coconut water, individually as well in combination, on in vitro shoot elongation and plant regeneration from cotyledon explants of C. annuum cv G-4. Shoot buds were induced on shoot bud induction medium supplemented with either 44.38 µM 6-benzylaminopurine (BAP) or 9.0 µM thidiazuron (TDZ) along with 5.77 µM gibberellic acid (GA3) and 14.7 µM phenyl acetic acid (PAA). Elongation of shoot buds was obtained on elongation medium containing 8.87 µM BA or 0.45 µM TDZ, 5.77 µM GA3 and 14.7 µM PAA followed by rooting in 9.8 µM indole-3-butyric acid (IBA). All the media were supplemented with 30 µM AgNO3 and/or coconut water (10% v/v). The presence of coconut water in the elongation media enhanced the regeneration of well developed shoots from differentiating explants on TDZ media while AgNO3 resulted in enhanced production of rooted shoots with greater influence on emerging shoots from BAP media upon transfer to rooting media. There was synergistic response with further enhancement of elongated shoots/elongated rooted shoots on the combined use of coconut water and AgNO3. The elongation media produced significantly higher total shoots when AgNO3 was used synergistically with coconut water (59.0%) as against AgNO3 alone (38.0%). While in rooting media, there was significantly higher production of elongated rooted shoots when coconut water was used synergistically with AgNO3 (47.2%) as against the coconut water alone (14.4%).

Protective role of selenium on pepper exposed to cadmium stress during reproductive stage.

The aim of the present study was to examine the effects of exogenous selenium (Se) supplementation on the tolerance of pepper (Capsicum annuum L.) cv. Suryamukhi Cluster plants to cadmium (Cd) phytotoxicity at the reproductive stage. The pepper plants were supplied with Cd (0, 0.25 or 0.50 mM) and Se (0, 3 or 7 µM), individually or simultaneously, three times during the experiment. The obtained results show that Cd had deleterious effect on pepper plants at the reproductive stage. However, Se supplementation improved the flower number, fruit number and fruit diameter in plants exposed to 0.50 mM Cd. Moreover, both Se concentrations used in 0.25 mM Cd-treated plants and 3 µM Se in 0.50 mM Cd-treated plants enhanced fruit yield per plant as compared to Cd-alone treatment. The chlorophyll concentrations significantly increased in the fruits of Cd-exposed plants after Se addition. However, Se supplementation reduced total carotenoids and total soluble solid (TSS) concentrations in the pepper fruits exposed to Cd. Selenium also generally enhanced the total antioxidant activity of pepper fruits subjected to Cd. Both Se concentrations used increased mean productivity (MP), stress tolerance index (STI) and yield stability index (YSI) in plants grown in the medium containing 0.25 mM Cd. At low concentration (3 µM), Se significantly increased geometric mean productivity (GMP), STI and YSI of plant exposed to 0.50 mM Cd. The highest Cd concentration in the fruits was achieved at 0.50 mM Cd and Se application significantly reduced Cd accumulation in the Cd-exposed plants. Our results indicate that application of Se can alleviate Cd toxicity in pepper plants at the reproductive stage by restricting Cd accumulation in fruits, enhancing their antioxidant activity and thus improving the reproductive and stress tolerance parameters.

Germination and ROS detoxification in bell pepper (Capsicum annuum L.) under NaCl stress and treatment with microalgae extracts.

We evaluated the salt tolerance of hybrids of pepper (Capsicum annuum L.) during germination. Treatments were applied at 0, 25, and 50 mM NaCl with preparations of supplemental extracts of the microalgae Dunaliella salina and Phaeodactylum tricornutum to determine the percentage germination rate as well as measured indicators of oxidative stress caused by the salt treatments during seed germination. We found that root growth was favorably influenced by the microalgae leading to increased germination rate. Tissues were analyzed in terms of superoxide radical production, lipid peroxidation, and activity of antioxidant enzymes viz. superoxide dismutase, catalase, and glutathione peroxidase. Our results suggest that application of microalgae extracts significantly reduced (p < 0.05) superoxide radical production, as well as lower lipid peroxidation in comparison to plants without extracts of microalgae. The antioxidant enzymes increased in the presence of microalgae showing a significant difference (p < 0.05). The results suggest differences in oxidative metabolism in response to the magnitude of salt stress and concentrations of microalgae help mitigate salt stress in plants during the germination process.

Root treatment with rhizobacteria antagonistic to Phytophthora blight affects anthracnose occurrence, ripening, and yield of pepper fruit in the plastic house and field.

We previously selected rhizobacterial strains CCR04, CCR80, GSE09, ISE13, and ISE14, which were antagonistic to Phytophthora blight of pepper. In this study, we investigated the effects of root treatment of rhizobacteria on anthracnose occurrence, ripening, and yield of pepper fruit in the plastic house and field in 2008 and 2009. We also examined the effects of volatiles produced by the strains on fruit ripening and on mycelial growth and spore development of Colletotrichum acutatum and Phytophthora capsici in the laboratory, identifying the volatile compounds by gas chromatography-mass spectrometry (GC-MS). In the house tests, all strains significantly (P < 0.05) reduced anthracnose incidence on pepper fruit; strains GSE09 and ISE14 consistently produced higher numbers of pepper fruit or increased the fresh weight of red fruit more than the controls in both years. In the field tests, all strains significantly (P < 0.05) reduced anthracnose occurrence on either green or red pepper fruit; strain ISE14 consistently produced higher numbers or increased fresh weights of red fruit more than the controls in both years. In the laboratory tests, volatiles produced by strains GSE09 and ISE13 only stimulated maturation of pepper fruit from green (unripe) to red (ripe) fruit; the volatiles of certain strains inhibited the growth and development of C. acutatum and P. capsici. On the other hand, GC-MS analysis of volatiles of strains GSE09 and ISE13 revealed 17 distinct compounds in both strains, including decane, dodecane, 1,3-di-tert-butylbenzene, tetradecane, 2,4-di-tert-butylphenol, and hexadecane. Among these compounds, 2,4-di-tert-butylphenol only stimulated fruit ripening and inhibited growth and development of the pathogens. Taken together, strains GSE09 and ISE14 effectively reduced anthracnose occurrence and stimulated pepper fruit ripening and yield, possibly via bacterial volatiles. Therefore, these two strains could be potential agents for controlling Phytophthora blight and anthracnose, and for increasing fruit ripening and yield. To our knowledge, this is the first report of volatiles such as 2,4-di-tert-butylphenol produced by rhizobacteria being related to both fruit ripening and pathogen inhibition.

Androgenesis in recalcitrant solanaceous crops.

Tomato, eggplant, and pepper are three solanaceous crops of outstanding importance worldwide. For hybrid seed production in these species, a fast and cheap method to obtain pure (homozygous) lines is a priority. Traditionally, pure lines are produced by classical inbreeding and selection techniques, which are time consuming (several years) and costly. Alternatively, it has become possible to accelerate the production of homozygous lines through a biotechnological approach: the induction of androgenesis to generate doubled haploid (homozygous) plants. This biotechnological in vitro tool reduces the process to only one generation, which implies important time and costs savings. These facts make androgenic doubled haploids the choice in a number of important crops where the methodology is well set up. Unfortunately, recalcitrant solanaceous crops such as tomato, eggplant, and pepper are still far from an efficient and reliable technology to be applied on a routine basis to different genotypes in breeding programs. In eggplant and pepper, only anther cultures are known to work relatively well. Unfortunately, a more efficient and promising technique, the culture of isolated microspores, is not sufficiently developed yet. In tomato, none of these methods is available nowadays. However, recent advances in the knowledge of embryo development are filling the gaps and opening new ways to achieve the final goal of an efficient protocol in these three recalcitrant species. In this review, we outline the state of the art on androgenic induction in tomato, eggplant, and pepper, and postulate new experimental ways in order to overcome current limitations.

CAZFP1, Cys2/His2-type zinc-finger transcription factor gene functions as a pathogen-induced early-defense gene in Capsicum annuum.

A pepper zinc-finger protein gene, CAZFP1 , encoding the Cys2/His2-type zinc-finger transcription factor was isolated from pepper leaves inoculated with an avirulent strain Bv5-4a of Xanthomonas campestris pv. vesicatoria . The CAZFP1 protein is a nuclear targeting protein, which functions as a transcriptional regulator. The full-length CAZFP1 had no transcriptional activation activity, whereas the C-terminal region of CAZFP1 had transactivation activity. The CAZFP1 transcripts were constitutively expressed in the pepper stem, root, flower and red fruit, but were not detectable in the leaf and green fruit. The CAZFP1 transcripts accumulated earlier than the CAZFP1 (PR-1) gene in the incompatible interaction of the pepper leaves with X. campestris pv. vesicatoria . The CAZFP1 transcripts were significantly induced in the systemic, uninoculated leaf tissues early after inoculation with bacterial pathogens, but gradually declined thereafter. The CAZFP1 transcripts were localized, and confined to the phloem cells of the vascular bundle in the pepper leaf midrib in response to Colletotrichum. coccodes infection, ethylene and abscisic acid. The CAZFP1 gene was also induced much earlier by abiotic elicitors and environmental stresses, compared with the CAZFP1 gene. Overexpression of the CAZFP1 gene in the transgenic Arabidopsis plants enhanced not only the resistance against infection by Pseudomonas syringae pv. tomato, but also the drought tolerance. These results suggest that the CAZFP1 gene functions as an early-defense gene to enhance disease resistance and drought tolerance.

Fructokinase and hexokinase from pollen grains of bell pepper (Capsicum annuum L.): possible role in pollen germination under conditions of high temperature and CO2 enrichment.

The processes of pollen grain development and germination depend on the uptake and metabolism of pollen sugars. In pepper (Capsicum annuum L.), initial sugar metabolism includes sucrose hydrolysis by invertase and subsequent phosphorylation of glucose and fructose by hexose kinases. The main objective of this study was to investigate changes in fructokinase (EC 2.7.1.4) and hexokinase (EC.2.7.1.1) activities in pepper flowers during their development, and to study the possible roles of these enzymes in determining pollen germination capacity under high temperature and under CO(2) enrichment, previously shown to modify sugar concentrations in pepper pollen (Aloni et al., 2001 Physiologia Plantarum 112: 505-512). Fructokinase (FK) activity was predominant in pepper pollen, and increased during pollen maturation. Pollen hexokinase (HK) activity was low and did not change throughout pollen development. High-temperature treatment (day/night, 32/26 degrees C) of pepper plants reduced the percentage of pollen that germinated compared with that under normal temperatures (26/22 degrees C), and concomitantly reduced the activity of FK in mature pollen. High temperature also reduced FK and HK activity in the anther. Under high ambient CO(2) (800 micro l l(-1)) pollen FK activity was enhanced. The results suggest that pollen and anther FK may play a role in the regulation of pollen germination, possibly by providing fructose-6-phosphate for glycolysis, or through conversion to UDP-glucose (UDPG) to support the biosynthesis of cell wall material for pollen tube growth. High temperature stress and CO(2) enrichment may influence pollen germination capacity by affecting these pathways.

Wound-inducible proteinase inhibitors in pepper. Differential regulation upon wounding, systemin, and methyl jasmonate.

Seven small (approximately 6,000 D) wound-inducible proteinase inhibitor proteins were isolated from leaves of pepper (Capsicum annuum) plants that are members of the potato inhibitor II family. N-terminal sequences obtained indicated that the pepper leaf proteinase inhibitors (PLPIs) exhibit homology to two GenBank accessions that code for preproteins containing three isoinhibitors domains each that, when post-translationally processed, can account for the mixture of isoinhibitors that are reported herein from pepper leaves. A constitutive level of PLPI proteins was found in pepper leaves, and these levels increased up to 2.6-fold upon wounding of the lower leaves. Exposing intact plants to methyl jasmonate vapors induced the accumulation of PLPIs. Supplying excised young pepper plants with water through the cut stems induced PLPI proteins to levels higher than those found in intact plants, but with high variability. Supplying the excised plants with systemin did not result in an increase of PLPI levels that were statistically higher than levels found in excised plants. Gel-blot analyses of PLPI induction revealed the presence of two mRNA bands, having slightly different mobilities in agarose gels. Only the low M(r) mRNA is present in untreated control plants, and it appears to be responsible for the constitutive levels of PLPI found in leaves. Both mRNA species are wound- and methyl jasmonate-inducible. Only the low- M(r) species is weakly induced by systemin, indicating a differential expression of the two PLPI species.