Transcriptome and Metabolome Reveal Key Genes from the Plant Hormone Signal Transduction Pathway Regulating Plant Height and Leaf Size in Capsicum baccatum.

Plant structure-related agronomic traits like plant height and leaf size are critical for growth, development, and crop yield. Defining the types of genes involved in regulating plant structure size is essential for the molecular-assisted breeding of peppers. This research conducted comparative transcriptome analyses using Capsicum baccatum germplasm HNUCB0112 and HNUCB0222 and their F2 generation as materials. A total of 6574 differentially expressed genes (DEGs) were detected, which contain 379 differentially expressed transcription factors, mainly including transcription factor families such as TCP, WRKY, AUX/IAA, and MYB. Seven classes of DEGs were annotated in the plant hormone signal transduction pathway, including indole acetic acid (IAA), gibberellin (GA), cytokinin (CK), abscisic acid (ABA), jasmonic acid (JA), ethylene (ET), and salicylic acid (SA). The 26 modules were obtained by WGCNA analysis, and the MEpink module was positively correlated with plant height and leaf size, and hub genes associated with plant height and leaf size were anticipated. Differential genes were verified by qRT-PCR, which was consistent with the RNA-Seq results, demonstrating the accuracy of the sequencing results. These results enhance our understanding of the developmental regulatory networks governing pepper key traits like plant height and leaf size and offer new information for future research on the pepper plant architecture system.

Impact of exogenous nicotine on the morphological, physio-biochemical, and anatomical characteristics in Capsicum annuum.

Nicotine is an alkaloid which only highly exists in tobacco plants. It accounts for 95% of its total alkaloid content. Nicotine is synthesized in the roots and transported via the xylem to the shoot. This study aimed to investigate the morphological, physio-biochemical, structural, and ultrastructural impacts of different nicotine concentrations in bell pepper. Capsicum annuum seedlings were grown hydroponically in a growth chamber with different nicotine concentrations (0, 100, 400, 700, 1,000, 3,000, and 5,000 µM). Nicotine-treated leaves (3,000 and 5,000 µM) exhibited severe chlorosis and necrosis. Moreover, nicotine-treated seedlings (1,000, 3,000, and 5,000 µM) exhibited severe reduction in leaf area (p < 0.0001) and photosynthetic efficiency (p < 0.0001), which significantly reduce the photosynthetic rate (p < 0.0001). Also, the drop in the photosynthetic rate was associated with significant drop in stomatal conductance (p < 0.0001). The electron transmission micrographs revealed that nicotine-treated seedlings (3,000 and 5,000 µM) exhibited deformed chloroplasts with numerous plastoglobules reducing the photosynthetic rates.

This is one of few studies that deal with the impact of exogenous nicotine on plants. However, to the best of our knowledge, this is the first hydroponic study that used liquid pure nicotine implied to the plants. The morphological, physio-biochemical, and anatomical characteristics were investigated using Capsicum annuum as a model plant, a plant that synthesizes little endogenous nicotine. This study will shed more light about nicotine toxicity in plants.

Multispectral Assessment of Sweet Pepper (Capsicum annuum L.) Fruit Quality Affected by Calcite Nanoparticles.

Sweet pepper (Capsicum annuum L.) is one of the most important vegetable crops in the world because of the nutritional value of its fruits and its economic importance. Calcium (Ca) improves the quality of sweet pepper fruits, and the application of calcite nanoparticles in agricultural practice has a positive effect on the morphological, physiological, and physicochemical properties of the whole plant. The objectives of this study were to investigate the effect of commercial calcite nanoparticles on yield, chemical, physical, morphological, and multispectral properties of sweet pepper fruits using a combination of conventional and novel image-based nondestructive methods of fruit quality analysis. In the field trial, two sweet pepper cultivars, i.e., Soroksari and Kurtovska kapija, were treated with commercial calcite nanoparticles (at a concentration of 3% and 5%, calcite-based foliar fertilizer (positive control), and water (negative control) three times during vegetation). Sweet pepper fruits were harvested at the time of technological and physiological maturity. Significant differences were observed between pepper cultivars as well as between harvests times. In general, application of calcite nanoparticles reduced yield and increased fruit firmness. However, different effects of calcite nanoparticles were observed on almost all properties depending on the cultivar. In Soroksari, calcite nanoparticles and calcite-based foliar fertilizers significantly increased N, P, K, Mg, Fe, Zn, Mn, and Cu at technological maturity, as well as P, Ca, Mg, Fe, Zn, Mn, Cu, and N at physiological maturity. However, in Kurtovska kapija, the treatments increased only Ca at technological maturity and only P at physiological maturity. The effect of treatments on fruit morphological properties was observed only at the second harvest. In Soroksari, calcite nanoparticles (3% and 5%) increased the fruit length, minimal circle area, and minimal circle radius, and it decreased the fruit width and convex hull compared to the positive and negative controls, respectively. In Kurtovska kapija, calcite nanoparticles increased the fruit width and convex hull compared to the controls. At physiological maturity, lower anthocyanin and chlorophyll indices were found in Kurtovska kapija in both treatments with calcite nanoparticles, while in Soroksari, the opposite effects were observed.

Capsaicinoid biosynthesis in the pericarp of chili pepper fruits is associated with a placental septum-like transcriptome profile and tissue structure.

KEY MESSAGE: CAP biosynthesis in the pericarp of chili pepper fruits occurs with an ambiguous boundary in the placental septum and pericarp. Capsaicinoid (CAP) is a pungent ingredient of chili pepper fruits. Generally, CAP biosynthesis is limited to the placental septum of fruits, but it has been reported that its biosynthesis occurs even in the pericarp of some extremely pungent varieties, resulting in a substantial increase in total content. To examine the mechanism of CAP biosynthesis in the pericarp, comparative transcriptome analysis of a variety that produces CAP in the pericarp (MY) and a variety that does not (HB) was carried out. RNA-seq revealed that 2264 genes were differentially expressed in the MY pericarp compared with the HB pericarp. PCA analysis and GO enrichment analysis indicated that the MY pericarp has a gene expression profile more like placental septum than the HB pericarp. The gene expression of CAP biosynthesis-related genes in the MY pericarp changed coordinately with the placental septum during fruit development. In most Capsicum accessions including HB, the distribution of slender epidermal cells producing CAP was limited to the placental septum, and the morphological boundary between the placental septum and pericarp was clear. In some extremely pungent varieties such as MY, slender epidermal cells ranged from the placental septum to the pericarp region, and the pericarp was morphologically similar to the placental septum, such as the absence of large sub-epidermal cells and abundant spaces in the parenchymal tissue. Our data suggest that CAP biosynthesis in the pericarp occurred with an ambiguous boundary in the placental septum and pericarp. These findings contribute to further enhancement of CAP production in chili pepper fruits.

Assessment of genetic divergence through cluster analysis of chilli varieties.

Our study on genetic diversity was conducted with six chilli genotypes with inter- and intra-specific cross varieties of the three most popular chilli species (Capsicum annuum L., Capsicum chinense Jacq., and Capsicum frutescens L.). Twelve quantitative characters, viz. plant height (cm), primary branches, secondary branches, number of flowers, number of fruits/plant; dry fruit weight (g), fruit length (cm), fruit diameter (cm), pedicel length (cm), pericarp thickness (mm), seeds/fruit, and seed weight (g), were taken into consideration. The analysis of variance revealed considerable variability among the genotypes for the character studied. Cluster analysis was used for grouping of parental and hybrid chilli genotypes under the study grouped into five clusters. Cluster I had the maximum (12) and clusters IVand V had the minimum number (1) of genotypes. The inter-cluster D2 values ranged between 40.404 and 127.530. The minimum inter-cluster distance was between clusters III and IV (40.404). The maximum inter-cluster distance was observed between clusters II and V (127.53). Diversity pattern and other horticultural performance among the genotypes of new varieties were generated due to the cross between Local Line Mahadev Pramanick and Sukhia bullet and also the cross between Local Line Mahadev Pramanick and Habanero orange (cluster II) as well as single parental variety i.e. Habanero orange. These genotypes were identified as promising varieties with respect to various characters may be taken into consideration as better parents for an efficient hybridization programme of chilli.

Three Strains of Tobacco etch virus Distinctly Alter the Transcriptome of Apical Stem Tissue in Capsicum annuum during Infection.

Tobacco etch virus (TEV; genus Potyvirus) is flexuous rod shaped with a single molecule of single-stranded RNA and causes serious yield losses in species in the Solanaceae. Three TEV strains (HAT, Mex21, and N) are genetically distinct and cause different disease symptoms in plants. Here, a transcriptomic RNA sequencing approach was taken for each TEV strain to evaluate gene expression of the apical stem segment of pepper plants during two stages of disease development. Distinct profiles of Differentially Expressed Genes (DEGs) were identified for each TEV strain. DEG numbers increased with degree of symptom severity: 24 from HAT, 1190 from Mex21, and 4010 from N. At 7 days post-inoculation (dpi), when systemic symptoms were similar, there were few DEGs for HAT- and Mex21-infected plants, whereas N-infected plants had 2516 DEGs. DEG patterns from 7 to 14 dpi corresponded to severity of disease symptoms: milder disease with smaller DEG changes for HAT and Mex21 and severe disease with larger DEG changes for N. Strikingly, in each of these comparisons, there are very few overlapping DEGs among the TEV strains, including no overlapping DEGs between all three strains at 7 or 14 dpi.

Specific leaf area is modulated by nitrogen via changes in primary metabolism and parenchymal thickness in pepper.

MAIN CONCLUSION: Nitrogen promotes changes in SLA through metabolism and anatomical traits in Capsicum plants. Specific leaf area (SLA) is a key trait influencing light interception and light use efficiency that often impacts plant growth and production. SLA is a key trait explaining growth variations of plant species under different environments. Both light and nitrogen (N) supply are important determinants of SLA. To better understand the effect of irradiance level and N on SLA in Capsicum chinense, we evaluated primary metabolites and morphological traits of two commercial cultivars (Biquinho and Habanero) in response to changes in both parameters. Both genotypes showed increased SLA with shading, and a decrease in SLA in response to increased N supply, however, with Habanero showing a stable SLA in the range of N deficiency to sufficient N doses. Correlation analyses indicated that decreased SLA in response to higher N supply was mediated by altered amino acids, protein, and starch levels, influencing leaf density. Moreover, in the range of moderate N deficiency to N sufficiency, both genotypes exhibited differences in SLA response, with Biquinho and Habanero displaying alterations on palisade and spongy parenchyma, respectively. Altogether, the results suggest that SLA responses to N supply are modulated by the balance between certain metabolites content and genotype-dependent changes in the parenchyma cells influencing leaf thickness and density.

Effects of red and blue light on leaf anatomy, CO2 assimilation and the photosynthetic electron transport capacity of sweet pepper (Capsicum annuum L.) seedlings.

BACKGROUND: The red (R) and blue (B) light wavelengths are known to influence many plant physiological processes during growth and development, particularly photosynthesis. To understand how R and B light influences plant photomorphogenesis and photosynthesis, we investigated changes in leaf anatomy, chlorophyll fluorescence and photosynthetic parameters, and ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) and Calvin cycle-related enzymes expression and their activities in sweet pepper (Capsicum annuum L.) seedlings exposed to four light qualities: monochromatic white (W, control), R, B and mixed R and B (RB) light with the same photosynthetic photon flux density (PPFD) of 300 µmol/m2·s. RESULTS: The results revealed that seedlings grown under R light had lower biomass accumulation, CO2 assimilation and photosystem II (PSII) electron transportation compared to plants grown under other treatments. These changes are probably due to inactivation of the photosystem (PS). Biomass accumulation and CO2 assimilation were significantly enriched in B- and RB-grown plants, especially the latter treatment. Their leaves were also thicker, and photosynthetic electron transport capacity, as well as the photosynthetic rate were enhanced. The up-regulation of the expression and activities of Rubisco, fructose-1, 6-bisphosphatase (FBPase) and glyceraldehyde-phosphate dehydrogenase (GAPDH), which involved in the Calvin cycle and are probably the main enzymatic factors contributing to RuBP (ribulose-1, 5-bisphosphate) synthesis, were also increased. CONCLUSIONS: Mixed R and B light altered plant photomorphogenesis and photosynthesis, mainly through its effects on leaf anatomy, photosynthetic electron transportation and the expression and activities of key Calvin cycle enzymes.

Cis- and Trans-Regulatory Variations in the Domestication of the Chili Pepper Fruit.

The process of domestication requires the rapid transformation of the wild morphology into the cultivated forms that humans select for. This process often takes place through changes in the regulation of genes, yet, there is no definite pattern on the role of cis- and trans-acting regulatory variations in the domestication of the fruit among crops. Using allele-specific expression and network analyses, we characterized the regulatory patterns and the inheritance of gene expression in wild and cultivated accessions of chili pepper, a crop with remarkable fruit morphological variation. We propose that gene expression differences associated to the cultivated form are best explained by cis-regulatory hubs acting through trans-regulatory cascades. We show that in cultivated chili, the expression of genes associated with fruit morphology is partially recessive with respect to those in the wild relative, consistent with the hybrid fruit phenotype. Decreased expression of fruit maturation and growth genes in cultivated chili suggest that selection for loss-of-function took place in its domestication. Trans-regulatory changes underlie the majority of the genes showing regulatory divergence and had larger effect sizes on gene expression than cis-regulatory variants. Network analysis of selected cis-regulated genes, including ARP9 and MED25, indicated their interaction with many transcription factors involved in organ growth and fruit ripening. Differentially expressed genes linked to cis-regulatory variants and their interactions with downstream trans-acting genes have the potential to drive the morphological differences observed between wild and cultivated fruits and provide an attractive mechanism of morphological transformation during the domestication of the chili pepper.

Effect of Root Restriction on the Growth, Photosynthesis Rate, and Source and Sink Relationship of Chilli (Capsicum annuum L.) Grown in Soilless Culture.

Chilli (Capsicum annum L.) plant is a high economic value vegetable in Malaysia, cultivated in soilless culture containers. In soilless culture, the adoption of small container sizes to optimize the volume of the growing substrate could potentially reduce the production cost, but will lead to a reduction of plant growth and yield. By understanding the physiological mechanism of the growth reduction, several potential measures could be adopted to improve yield under restricted root conditions. The mechanism of growth reduction of plants subjected to root restriction remains unclear. This study was conducted to determine the physiological mechanism of growth reduction of root-restricted chilli plants grown in polyvinyl-chloride (PVC) column of two different volumes, 2392 cm3(root-restricted) and 9570 cm3(control) in soilless culture. Root restriction affected plant growth, physiological process, and yield of chilli plants. Root restriction reduced the photosynthesis rate and photochemical activity of PSII, and increased relative chlorophyll content. Limited root growth in root restriction caused an accumulation of high levels of sucrose in the stem and suggested a transition of the stem as a major sink organ for photoassimilate. Growth reduction in root restriction was not related to limited carbohydrate production, but due to the low sink demand from the roots. Reduction of the total yield per plant about, 23% in root restriction was concomitant, with a slightly increased harvest index which reflected an increased photoassimilate partitioning to the fruit production and suggested more efficient fruits production in the given small plant size of root restriction.

Analysis of candidate genes expression associated with defense responses to root and collar rot disease caused by Phytophthora capsici in peppers Capsicum annuum.

Root and collar rot disease caused by Phytophthora capsici (Leonian) is one of the most serious diseases in pepper, Capsicum annuum L. Knowledge about resistant genes is limited in pepper accessions to P. capsici. In this study, a diverse collection of 37 commercial edible and ornamental genotypes, and implication of seven novel candidate DEGs genes (XLOC_ 021757, XLOC_021821, XLOC_012788, XLOC_011295, XLOC_021928, XLOC_015473 and XLOC_000341) were up-regulated on resistant and susceptible pepper cultivars, through real-time polymerase chain reaction (qPCR) at transplanting and maturing stages. All seven related defense-gene candidates were up-regulated in all inoculated accessions to P. capsici, but these genes were highly expressed in resistant ones, 19OrnP-PBI, 37ChillP-Paleo, and 23CherryP-Orsh. The transcriptional levels of the seven related candidate DEGs were 5.90, 5.64, 5.62, 5.18, 3.94, 3.69, 3.16 folds higher in the resistant pepper genotypes, than the control ones, non-inoculated genotypes respectively. The candidate genes expressed herein, will provide a basis for further gene cloning and functional verification studies, and also will aid in an understanding of the regulatory mechanism of pepper resistance to P. capsici.

Target sequencing reveals genetic diversity, population structure, core-SNP markers, and fruit shape-associated loci in pepper varieties.

BACKGROUND: The widely cultivated pepper (Capsicum spp.) is one of the most diverse vegetables; however, little research has focused on characterizing the genetic diversity and relatedness of commercial varieties grown in China. In this study, a panel of 92 perfect single-nucleotide polymorphisms (SNPs) was identified using re-sequencing data from 35 different C. annuum lines. Based on this panel, a Target SNP-seq genotyping method was designed, which combined multiplex amplification of perfect SNPs with Illumina sequencing, to detect polymorphisms across 271 commercial pepper varieties. RESULTS: The perfect SNPs panel had a high discriminating capacity due to the average value of polymorphism information content, observed heterozygosity, expected heterozygosity, and minor allele frequency, which were 0.31, 0.28, 0.4, and 0.31, respectively. Notably, the studied pepper varieties were morphologically categorized based on fruit shape as blocky-, long horn-, short horn-, and linear-fruited. The long horn-fruited population exhibited the most genetic diversity followed by the short horn-, linear-, and blocky-fruited populations. A set of 35 core SNPs were then used as kompetitive allele-specific PCR (KASPar) markers, another robust genotyping technique for variety identification. Analysis of genetic relatedness using principal component analysis and phylogenetic tree construction indicated that the four fruit shape populations clustered separately with limited overlaps. Based on STRUCTURE clustering, it was possible to divide the varieties into five subpopulations, which correlated with fruit shape. Further, the subpopulations were statistically different according to a randomization test and Fst statistics. Nine loci, located on chromosomes 1, 2, 3, 4, 6, and 12, were identified to be significantly associated with the fruit shape index (p < 0.0001). CONCLUSIONS: Target SNP-seq developed in this study appears as an efficient power tool to detect the genetic diversity, population relatedness and molecular breeding in pepper. Moreover, this study demonstrates that the genetic structure of Chinese pepper varieties is significantly influenced by breeding programs focused on fruit shape.

Potential of pepper plant accessions for ornamental purposes using diallel analysis.

The genus Capsicum is cultivated in various parts of the world, with C. annuum showing high diversity and potential for ornamental purposes and genetic improvement. The aim of this work was to evaluate the combining ability and heterosis of seedling and plant traits in accessions of ornamental pepper and their hybrids. Seven accessions of C. annuum were handcrossed and twelve quantitative plant traits were evaluated. The data were subjected to analysis of variance, the Scott-Knott test and diallel analysis using Griffing's method I (fixed model). Heterosis and its components were also determined. Non-additive effects were found for seedling height, cotyledonous leaf length and width; stem diameter and chlorophyll b content. All other traits showed predominance of additive effects. Heterosis effects were found for some hybrids and UFPB134 x UFPB137, UFPB134 x UFPB390, UFPB134 x UFPB004 and UFPB099 x UFPB004 showed seedlings that are more vigorous.

Genome-wide identification of glutathione S-transferase gene family in pepper, its classification, and expression profiling under different anatomical and environmental conditions.

Glutathione S-transferases (GSTs) compose a family of multifunctional enzymes involved in the numerous aspects of regulating plant growth, development, and stress response. An in silico genome-wide analysis of pepper (Capsicum annuum L.) was performed to identify eighty-five GST genes that were annotated according to their chromosomal location. Segmental duplication contributed more than tandem duplication for the expansion of GST gene family in pepper. All the identified members belong to ten different classes which are highly conserved among Arabidopsis, rice, tomato and potato counterparts indicating the pre-dicot-monocot split diversification of GST classes. Gene structure, protein domain, and motif organization were found to be notably conserved over the distinct phylogenetic groups, which demonstrated the evolutionary significant role of each class. Expression of most of the CaGST transcripts as well as the total pepper GST activity was found to be significantly up-regulated in response to cold, heat, drought, salinity and osmotic stress conditions. Presence of various hormone and stress-responsive cis-elements on most of the putative CaGST promoter regions could be directly correlated with the alteration of their transcripts. All these findings might provide opportunities for future functional validation of this important gene family in pepper.

Automatic Parameter Tuning for Adaptive Thresholding in Fruit Detection.

This paper presents an automatic parameter tuning procedure specially developed for a dynamic adaptive thresholding algorithm for fruit detection. One of the major algorithm strengths is its high detection performances using a small set of training images. The algorithm enables robust detection in highly-variable lighting conditions. The image is dynamically split into variably-sized regions, where each region has approximately homogeneous lighting conditions. Nine thresholds were selected to accommodate three different illumination levels for three different dimensions in four color spaces: RGB, HSI, LAB, and NDI. Each color space uses a different method to represent a pixel in an image: RGB (Red, Green, Blue), HSI (Hue, Saturation, Intensity), LAB (Lightness, Green to Red and Blue to Yellow) and NDI (Normalized Difference Index, which represents the normal difference between the RGB color dimensions). The thresholds were selected by quantifying the required relation between the true positive rate and false positive rate. A tuning process was developed to determine the best fit values of the algorithm parameters to enable easy adaption to different kinds of fruits (shapes, colors) and environments (illumination conditions). Extensive analyses were conducted on three different databases acquired in natural growing conditions: red apples (nine images with 113 apples), green grape clusters (129 images with 1078 grape clusters), and yellow peppers (30 images with 73 peppers). These databases are provided as part of this paper for future developments. The algorithm was evaluated using cross-validation with 70% images for training and 30% images for testing. The algorithm successfully detected apples and peppers in variable lighting conditions resulting with an F-score of 93.17% and 99.31% respectively. Results show the importance of the tuning process for the generalization of the algorithm to different kinds of fruits and environments. In addition, this research revealed the importance of evaluating different color spaces since for each kind of fruit, a different color space might be superior over the others. The LAB color space is most robust to noise. The algorithm is robust to changes in the threshold learned by the training process and to noise effects in images.

Effect of UV-B radiation on morphology, phenolic compound production, gene expression, and subsequent drought stress responses in chili pepper (Capsicum annuum L.).

It has been suggested that accumulation of flavonoids could be a key step in development of plant tolerance to different environmental stresses. Moreover, it has been recognized that abiotic stresses such as drought and UV-B radiation (280-315 nm) induce phenolic compound accumulation, suggesting a role for these compounds in drought tolerance. The aim of the present study was to evaluate the effect of UV-B exposure on chili pepper (Capsicum annuum, cv. 'Coronel') plant performance, phenolic compound production, and gene expression associated with response to subsequent drought stress. Additionally, the phenotypic response to drought stress of these plants was studied. UV-B induced a reduction both in stem length, stem dry weight and number of floral primordia. The largest reduction in these variables was observed when combining UV-B and drought. UV-B-treated well-watered plants displayed fructification approximately 1 week earlier than non-UV-B-treated controls. Flavonoids measured epidermally in leaves significantly increased during UV-B treatment. Specifically, UV-B radiation significantly increased chlorogenic acid and apigenin 8-C-hexoside levels in leaves and a synergistic increase of luteolin 6-C-pentoside-8-C-hexoside was obtained by UV-B and subsequent drought stress. Gene expression of phenylalanine ammonia lyase (PAL) and chalcone synthase (CHS) genes also increased during UV-B treatments. On the other hand, expression of genes related to an oxidative response, such as mitochondrial Mn-superoxide dismutase (Mn-SOD) and peroxidase (POD) was not induced by UV-B. Drought stress in UV-B-treated plants induced mitochondrial Mn-SOD gene expression. Taken together, the UV-B treatment did not induce significant tolerance in plants towards drought stress under the conditions used.

Development of the ovule and seed of Habanero chili pepper (Capsicum chinense Jacq.): Anatomical characterization and immunocytochemical patterns of pectin methyl-esterification.

Ovule and seed development in plants has long fascinated the scientific community given the complex cell coordination implicated in these processes. These cell events are highly conserved but are not necessarily representative of all plants. In this study, with the aim of obtaining information regarding the cellular patterns that follow the usual development of the ovule and the zygotic embryo, we carried out an integral anatomical study of the Capsicum chinense Jacq., floral buds and seeds at various days during maturation. This study allowed us to identify the main histo-morphological stages accompanying the transition of somatic cells into the macrospore, female gamete, and the zygotic embryogenesis. This knowledge is fundamental for future biotechnological research focused on solving the morphological recalcitrance observed during the in vitro induction of somatic or microspore embryogenesis in Capsicum. For the first time in C. chinense, we have described the hypostases, a putative source of plant growth regulators, and "the corrosion cavity", a space around the embryo. Additionally, the cell wall pectin-esterification status was investigated by immunohistology. At early stages of morphogenesis, the pectin is highly methyl-esterified; however, methyl-esterification decreases gradually throughout the process. A comparison of the results obtained here, together with the histo- and immunological changes occurring during the somatic and microspore embryogenesis, should help to elucidate the biochemical mechanisms that trigger the morphogenic events in Capsicum spp.

Genetic variability in Brazilian Capsicum baccatum germplasm collection assessed by morphological fruit traits and AFLP markers.

Capsicum baccatum is one of the main pepper species grown and consumed in South America. In Brazil, it is commonly cultivated by family farmers, using mostly the genotypes bishop's hat genotypes (locally cambuci) and red chili pepper (dedo-de-moça). This study had the objective of characterizing 116 C. baccatum accessions from different regions of Brazil, based on morphological fruit descriptors and AFLP (Amplified Fragment Length Polymorphisms) markers. Broad phenotypic variability among the C. baccatum accessions was detected when using morphological fruit descriptors. The Ward modified location model (Ward-MLM) discriminated five groups, based mainly on fruit shape. Six combinations of AFLP primers detected polymorphism in 97.93% of the 2466 identified bands, indicating the high genetic variability in the accessions. The UPGMA coincided with the Bayesian clustering analysis and three large groups were formed, separating the wild variety C. baccatum var. praetermissum from the other accessions. There was no relation between genetic distance and geographical origin of the accessions, probably due to the intense exchange of fruits and seeds between farmers. Morphological descriptors used together with AFLP markers proved efficient in detecting the levels of genetic variability among the accessions maintained in the germplasm collections. These results can be used as an additional source of helpful information to be exploited in C. baccatum breeding programs.

New insights into the cellular responses to iron nanoparticles in Capsicum annuum.

In this study, the anatomical and ultrastructural responses of Capsicum annuum to iron nanoparticles (Fe NPs) were determined. The results showed that the bio-effects of Fe NPs on plants could be positive or negative, depending on the additive concentrations. Low concentrations of Fe NPs were found to promote plant growth. Light and electron microscope analyses showed that the Fe NPs promoted plant growth by altering the leaf organization, and increasing the chloroplast number and grana stacking, as well as regulating the development of vascular bundles. Meanwhile, it was found that the Fe NPs could be absorbed in the roots, and then transported to the central cylinder in bio-available forms, where they were translocated and utilized by the leaves and stems. In contrast, high concentrations of Fe NPs appeared to be harmful to the plants, and the majority of Fe NPs were aggregated into cell walls and transported via the apoplastic pathway in the roots, which may potentially block the transfer of iron nutrients. Taken together, the aforementioned data showed that the rational use of Fe NPs could alleviate iron deficiency, and Fe NPs could be an ideal supply for Fe2+ ions fertilizers in agriculture.

Changes in Membrane Lipid Composition and Function Accompanying Chilling Injury in Bell Peppers.

Bell peppers are vulnerable to low temperature (<7°C) and subject to chilling injury (CI). To elucidate the relationship between cell membrane lipid composition and CI, a membrane lipidomic approach was taken. In addition, we performed microstructural analysis and low-field nuclear magnetic resonance to better understand CI. We also monitored primary physiological metabolism parameters to explain lipidomics. Our study indicated that cellular structure damage was more serious at 4°C, mostly represented by damage to the plasmalemma and plastid degradation. Membrane lipidomic data analysis reveals monogalactosyldiacylglycerol, phosphatidylcholine, phosphatidylethanolamine and phosphatidic acid as crucial biomarkers during CI. Furthermore, the significant increase in proline, electrolyte leakage and phospholipase D in chilled fruits also proved that membrane lipid metabolism is involved in the response to low temperature stress. To our knowledge, this study is the first attempt to describe the CI mechanisms in bell peppers based on membrane lipidomics.