Mendel-200: Pea as a model system to analyze hormone-mediated stem elongation

In a recent Review Article on Gregor Mendel's (1822-1884) work with pea (Pisum sativum)-plants, it was proposed that this crop species should be re-vitalized as a model organism for the study of cell- and organ growth. Here, we describe the effect of exogenous gibberellic acid (GA3) on the growth of the second internode in 4-day-old light-grown pea seedlings (Pisum sativum, large var. "Senator"). lnjection of glucose into the internode caused a growth-promoting effect similar to that of the hormone GA3. Imbibition of dry pea seeds in GA3, or water as control, resulted in a drastic enhancement in organ development in this tall variety. Similar results were reported for dwarf peas. These "classical" experimental protocols are suitable to study the elusive effect of gibberellins (which act in coordination with auxin) on the regulation of plant development at the biochemical and molecular levels.

Cladosporium cladosporioides causes leaf blight on garden pea in Telangana, India

Garden pea (Pisum sativum L.) is an important vegetable and pulse crop grown worldwide. Leaf blight symptoms with chlorotic lesions were observed on the pea genotypes, 2006-2008A and Arkel in field conditions at Asian Vegetable Research and Development Centre (AVRDC), Hyderabad (17°23' N; 78°29' E) and greenhouse conditions at University of Hyderabad, Hyderabad, India (17° 27' N; 78° 19' E) since 2010. The blight symptoms showed black lesions coated by a fine velvety layer of olive-grey conidia. The disease incidence on field and greenhouse pea plants ranged from 3-6%. The Cladosporium isolates, Gp01 and Gp02 were isolated from pea genotypes, Arkel and 2006-2008A in greenhouse and field conditions respectively. One fungus was predominantly isolated from infected leaf tissue plated onto potato dextrose agar (PDA), and it was identified as Cladosporium sp. based on colony morphology and conidial appearance. Single-spored cultures grown at 26±2 °C on PDA showed olive green mycelia on the obverse-side and dark green on reverse-side (Fig. 1 a,b). The conidia were limoniform with dimensions ranging from 5.91-7.33 x 3.19-4.58 µm (Table 1) and were produced on solitary conidiophores containing 1-2 septa, with no constriction whereas the aerial hyphae were septate and unbranched or rarely branched (Fig.1 c-d). To verify the pathogenicity of the fungus, detached leaf assay was carried on 30-day old Arkel leaves by point inoculation with 20 µL (106 spores/ml) spore suspension using a needle-less syringe to infiltrate the spores into the abaxial surface and the inoculated leaves were incubated at 26±2 °C for 3 days in petri plates containing moistened autoclaved absorbent cotton. Pea leaves inoculated with water served as controls. The experiment was repeated with a minimum of three times with five leaves per replication and three replications per experiment for each of the isolates. The appressorial germ tube formation was observed by scanning electron microscopy (SEM) at 12 hours post inoculation (hpi) (Fig.1 e-f). Thirty-day old pea plants were spray-inoculated with a spore suspension of 1-2 ml per plant with a concentration of 106 spores/ ml while the control plants were mock-inoculated (sprayed) with water. 5 plants per replicate per isolate with three replications per experiment and a minimum of three experiments were carried. The inoculated plants were covered with polythene zip-lock bags for two days post inoculation (dpi) and maintained in greenhouse at 26±2 °C with natural photoperiod of 14 hours. Wilting and necrosis symptoms accompanied by chlorotic lesions were observed on pea plants at 7 days post inoculation (dpi) (Fig. 2). Complying with Koch's postulates, the pathogen, which was re-isolated from the first appearance at 3 dpi from infected pea showed similar morphological characteristics as those used for inoculation. Sequencing analysis of the internal transcribed spacer (ITS) region using ITS1 and ITS4 primers (White et al. 1990), D1-D2 region sequencing (Kwiatkowski et al. 2012), Translation elongation factor 1-alpha (TEF) and Actin (ACT) gene sequencing (Nam et al. 2015) of Gp01 and Gp02 showed significant similarity with C. cladosporioides (Table S1). Further, concatenated phylogenetic trees constructed by maximum likelihood method using all the four (ITS, D1-D2, TEF and ACTIN) gene sequences of these isolates along with other reported Cladosporium species (Fig. S1a) and specific isolates of C. cladosporiodes which are reported as "sensu stricto" (Bensch et al. 2010) collected from different substrata (Fig. S1b) confirmed them as C. cladosporioides. Gp01 and Gp02 were also confirmed by Microbial Type Culture Collection (MTCC, India) as C. cladosporioides with Acc. No. MTCC 9994 and MTCC 9995. C. cladosporioides has been previously reported on Dalbergia sp. and Eucalyptus sp in India and on garden pea in other countries (Bensch et al. 2010). However, owing to the impact of this pathogen on growth and productivity of pea crop, further in-depth study needs to be carried. To our understanding this is the first report of Cladosporium cladosporioides infecting garden pea in India.

Effects of Salinity and Abscisic Acid on Lipid Transfer Protein Accumulation, Suberin Deposition and Hydraulic Conductance in Pea Roots

Lipid transfer proteins (LTPs) participate in many important physiological processes in plants, including adaptation to stressors, e.g., salinity. Here we address the mechanism of this protective action of LTPs by studying the interaction between LTPs and abscisic acid (ABA, a "stress" hormone) and their mutual participation in suberin deposition in root endodermis of salt-stressed pea plants. Using immunohistochemistry we show for the first time NaCl induced accumulation of LTPs and ABA in the cell walls of phloem paralleled by suberin deposition in the endoderm region of pea roots. Unlike LTPs which were found localized around phloem cells, ABA was also present within phloem cells. In addition, ABA treatment resulted in both LTP and ABA accumulation in phloem cells and promoted root suberization. These results suggested the importance of NaCl-induced accumulation of ABA in increasing the abundance of LTPs and of suberin. Using molecular modeling and fluorescence spectroscopy we confirmed the ability of different plant LTPs, including pea Ps-LTP1, to bind ABA. We therefore hypothesize an involvement of plant LTPs in ABA transport (unloading from phloem) as part of the salinity adaptation mechanism.

Trait Expression and Environmental Responses of Pea (Pisum sativum L.) Genetic Resources Targeting Cultivation in the Arctic

In the Arctic part of the Nordic region, cultivated crops need to specifically adapt to adverse and extreme climate conditions, such as low temperatures, long days, and a short growing season. Under the projected climate change scenarios, higher temperatures and an earlier spring thaw will gradually allow the cultivation of plants that could not be previously cultivated there. For millennia, Pea (Pisum sativum L.) has been a major cultivated protein plant in Nordic countries but is currently limited to the southern parts of the region. However, response and adaptation to the Arctic day length/light spectrum and temperatures are essential for the productivity of the pea germplasm and need to be better understood. This study investigated these factors and identified suitable pea genetic resources for future cultivation and breeding in the Arctic region. Fifty gene bank accessions of peas with a Nordic landrace or cultivar origin were evaluated in 2-year field trials at four Nordic locations in Denmark, Finland, Sweden, and Norway (55° to 69° N). The contrasting environmental conditions of the trial sites revealed differences in expression of phenological, morphological, crop productivity, and quality traits in the accessions. The data showed that light conditions related to a very long photoperiod partly compensated for the lack of accumulated temperature in the far north. A critical factor for cultivation in the Arctic is the use of cultivars with rapid flowering and maturation times combined with early sowing. At the most extreme site (69°N), no accession reached full maturation. Nonetheless several accessions, predominantly landraces of a northern origin, reached a green harvest state. All the cultivars reached full maturation at the sub-Arctic latitude in northern Sweden (63°N) when plants were established early in the season. Seed yield correlated positively with seed number and aboveground biomass, but negatively with flowering time. A high yield potential and protein concentration of dry seed were found in many garden types of pea, confirming their breeding potential for yield. Overall, the results indicated that pea genetic resources are available for breeding or immediate cultivation, thus aiding in the northward expansion of pea cultivation. Predicted climate changes would support this expansion.

Comparative transcriptome of compatible and incompatible interaction of Erysiphe pisi and garden pea reveals putative defense and pathogenicity factors

Comparative transcriptome analysis of Erysiphe pisi-infected pea (Pisum sativum) genotypes JI-2480 (resistant) and Arkel (susceptible) at 72 hours post-inoculation (hpi) was carried to detect molecular components involved in compatible and incompatible interactions. Differential gene expression was observed in Arkel and JI-2480 genotype at 72 hpi with E. pisi isolate (Ep01) using EdgeR software. Out of 32 217 transcripts, 2755 transcripts showed significantly altered gene expression in case of plants while 530 were related to E. pisi (P < 0.05). The higher transcript number of differentially expressed genes demonstrated peak activity of pathogenicity genes in plants at 72 hpi. Glycolysis was observed to be the major pathway for energy source during fungal growth. Differential gene expression of plant transcripts revealed significant expression of putative receptor and regulatory sequences involved in defense in the resistant, JI-2480 compared to susceptible, Arkel genotype. Expression of genes involved in defense and hormonal signaling, genes related to hypersensitive response, reactive oxygen species and phenylpropanoid pathway in JI-2480 indicated their crucial role in disease resistance against E. pisi. Down-regulation of transcription factors like-WRKY-28 and up-regulation of several putative pattern recognition receptors in JI-2480 compared to Arkel also suggested activation of host-mediated defense responses against E. pisi in pea.

A high coverage reference transcriptome assembly of pea (Pisum sativum L.) mycorrhizal roots

Arbuscular mycorrhiza (AM) is an ancient mutualistic symbiosis formed by 80–90 % of land plant species with the obligatorily biotrophic fungi that belong to the phylum Glomeromycota. This symbiosis is mutually beneficial, as AM fungi feed on plant photosynthesis products, in turn improving the efficiency of nutrient uptake from the environment. The garden pea (Pisum sativum L.), a widely cultivated crop and an important model for genetics, is capable of forming triple symbiotic systems consisting of the plant, AM fungi and nodule bacteria. As transcriptomic and proteomic approaches are being implemented for studying the mutualistic symbioses of pea, a need for a reference transcriptome of genes expressed under these specific conditions for increasing the resolution and the accuracy of other methods arose. Numerous transcriptome assemblies constructed for pea did not include mycorrhizal roots, hence the aim of the study to construct a reference transcriptome assembly of pea mycorrhizal roots. The combined transcriptome of mycorrhizal roots of Pisum sativum cv. Frisson inoculated with Rhizophagus irregularis BEG144 was investigated, and for both the organisms independent transcriptomes were assembled (coverage 177x for pea and 45x for fungus). Genes specific to mycorrhizal roots were found in the assembly, their expression patterns were examined with qPCR on two pea cultivars, Frisson and Finale. The gene expression depended on the inoculation stage and on the pea cultivar. The investigated genes may serve as markers for early stages of inoculation in genetically diverse pea cultivars.

Functional Amyloids Germinate in Plants

First identified in human disorders, amyloids serve biological functions in bacteria, archaea, fungi, and animals; however, their role in plants has remained unexplored. Recently, Antonets et al. identified a functional amyloid in plants, with a crucial role in seed longevity, confirming that amyloids are universally exploited for organisms' adaptation.

Transcriptomic Insights into Mechanisms of Early Seed Maturation in the Garden Pea (Pisum sativum L.)

The garden pea (Pisum sativum L.) is a legume crop of immense economic value. Extensive breeding has led to the emergence of numerous pea varieties, of which some are distinguished by accelerated development in various stages of ontogenesis. One such trait is rapid seed maturation, which, despite novel insights into the genetic control of seed development in legumes, remains poorly studied. This article presents an attempt to dissect mechanisms of early maturation in the pea line Sprint-2 by means of whole transcriptome RNA sequencing in two developmental stages. By using a de novo assembly approach, we have obtained a reference transcriptome of 25,756 non-redundant entries expressed in pea seeds at either 10 or 20 days after pollination. Differential expression in Sprint-2 seeds has affected 13,056 transcripts. A comparison of the two pea lines with a common maturation rate demonstrates that while at 10 days after pollination, Sprint-2 seeds show development retardation linked to intensive photosynthesis, morphogenesis, and cell division, and those at 20 days show a rapid onset of desiccation marked by the cessation of translation and cell anabolism and accumulation of dehydration-protective and -storage moieties. Further inspection of certain transcript functional categories, including the chromatin constituent, transcription regulation, protein turnover, and hormonal regulation, has revealed transcriptomic trends unique to specific stages and cultivars. Among other remarkable features, Sprint-2 demonstrated an enhanced expression of transposable element-associated open reading frames and an altered expression of major maturation regulators and DNA methyltransferase genes. To the best of our knowledge, this is the first comparative transcriptomic study in which the issue of the seed maturation rate is addressed.

Prediction models for evaluating heavy metal uptake by Pisum sativum L. in soil amended with sewage sludge

The present study aims to develop prediction models for estimating the potential uptake of 10 heavy metals (HMs) (cadmium, Cd; cobalt, Co; chromium, Cr; copper, Cu; iron, Fe; manganese, Mn; molybdenum, Mo; nickel, Ni; lead, Pb; zinc, Zn) by the tissues of Pisum sativum (root, shoot and pod) grown in soil amended with sewage sludge (SS) under greenhouse conditions. Soil organic matter (OM) was estimated by loss-on-ignition at 550 °C for 2 h. The pH was determined by shaking the soil and pure water at a 1:5 ratio. For HM quantifications, 0.5-1.0 g of each soil or plant sample was digested using a tri-acid mixture digestion method. The quantities of selected HMs were estimated by means of inductively coupled plasma optical emission spectrometry. Bio-concentration (BCF) and translocation (TF) factors were <1 for most of the HMs. In addition, simple linear correlations were significantly negative between the BCF of all studied HMs and soil pH, except for Pb, Mn and Ni, whereas significant positive correlations were observed between BCFs and soil OM, except for Mn, Ni and Zn. The accumulation of the 10 HMs in P. sativum tissues was predicted using regression models based on the values of the same HM in the soil as well as its pH and OM. The calculated prediction models performed well for most HMs in P. sativum tissues (except Ni in the pod, Cd in the shoot and Mn in the root). All measured soil factors (HM, pH and OM) consistently contributed to HM concentrations in the three tissues of the studied plants. These models may help to evaluate the safe cultivation of this species in soil amended with SS.

Facile green biosynthesis of silver nanoparticles using Pisum sativum L. outer peel aqueous extract and its antidiabetic, cytotoxicity, antioxidant, and antibacterial activity

BACKGROUND

The synthesis of silver nanoparticles (AgNPs) using food waste materials and their biomedical applications have garnered considerable attention recently.

METHODS

Here, we investigated the synthesis of AgNPs using an aqueous extract of outer peel of Pisum sativum under different lighting conditions using standard procedures and explored their antidiabetic, cytotoxicity, antioxidant, and antibacterial potential.

RESULTS

Characterization of AgNPs was done by Ultra Violet (UV-VIS) spectroscopy that showed absorption maxima at 456 nm for the samples exposed to laboratory lighting and at 464 nm for the samples exposed to direct sunlight, by scanning electron microscopy and energy-dispersive X-ray analysis that showed the surface nature and their elemental composition with a strong peak at 3 keV that corresponded to Ag (61.85 wt%), by Fourier-transform infrared spectroscopy that predicted the functional groups involved, and by X-ray powder diffraction that showed the structural properties. The average diameter of the synthesized AgNPs was calculated to be in the range of 10-25 nm. AgNPs exhibited promising antidiabetic activity as determined by inhibition of α-glucosidase (95.29% inhibition at 10 µg/mL and IC50 value of 2.10 µg/mL) and cytotoxicity (IC50 value 4.0 µg/mL as calculated from the slope equation) against HepG2 cells. Furthermore, they also exhibited moderate antioxidant activity (50.17% reduction of 1,1-diphenyl-2-picrylhydrazyl at 100 µg/mL) and antibacterial activity against four human pathogenic bacteria (as indicated by 8.70-11.10 mm inhibition zones on agar plates).

CONCLUSION

In conclusion, the results confirm that food waste can be used in the synthesis of AgNPs and that the latter have the potential for applications in various fields including diabetic and cancer treatments as well as in biomedicine for the manufacture of antibacterial coatings in medical devices and instruments.

Molecular dissection of the pea shoot apical meristem

The shoot apical meristem (SAM) is responsible for the development of all the above-ground parts of a plant. Our understanding of the SAM at the molecular level is incomplete. This study investigates the gene expression repertoire of SAMs in the garden pea (Pisum sativum). To this end, 10 346 EST sequences representing 7610 unique genes were generated from SAM cDNA libraries. These sequences, together with previously reported pea ESTs, were used to construct a 12K oligonucleotide array to identify genes with differential SAM expression, as compared to axillary meristems, root apical meristems, or non-meristematic tissues. A number of genes were identified, predominantly expressed in specific cell layers or domains of the SAM and thus are likely components of the gene networks involved in stem cell maintenance or the initiation of lateral organs. Further in situ hybridization analysis confirmed the spatial localization of some of these genes within the SAM. Our data also indicate the diversification of some gene expression patterns and hence functions in legume crop plants. A number of transcripts highly expressed in all three meristems have also been uncovered and these candidates may provide valuable insight into molecular networks that underpin the maintenance of meristematic functionality.