Mature Pea Research Articles

Effect of chronic ultraviolet b radiation on pea plants

Aim. The effect of chronic ultraviolet B (UV-B) radiation on shoots growth, content of photosynthetic pigments and hydrogen peroxide (HP) in the leaves of pea plants (Pisum sativum L.) was studied. Methods. Pea plants cultivar Gotivsky were irradiated by chronic UV-B during 5 days in the doses from 2.5 to 4 kJ/m2 per day with a power of 1 W/m2. The length of plant shoots was measured during 7 days after the end of radiation. Content of photosynthetic pigments and HP in leaves were measured on the 7 day after radiation. Results. It was shown that after the chronic UV-B radiation of pea plants with doses from 2.5 to 4 kJ/m2 per day, the length of shoots increased, most significantly after the dose of 3 kJ/m2 per day. Content of HP in mature leaves was in 2 times higher than the level of control in all variants, the content of chlorophyll and carotenoids decreased compared to the control, most significantly after a dose 4 kJ/m2 per day. Conclusions. It was shown that after the UV-B chronic radiation with doses from 2.5 to 4 kJ/m2 per day of pea plants, shoot growth increased. The content of HP in mature leaves increased, the content of photosynthetic pigments decreased. The chronic UV-B radiation caused the destruction of the pigment complex of mature pea leaves and oxidative stress, but the absence of UV-B in the light can cause the decrease of growth.

Combination of electronically driven micromanipulation with laser desorption ionization mass spectrometry - The unique tool for analysis of seed coat layers and revealing the mystery of seed dormancy.

Electronically driven micromanipulation (EDM) with microscopic control was used as a novel tool for sample preparation prior to direct (matrix assisted) laser desorption/ionization mass spectrometric ((MA)LDI-MS) analysis of mature pea seed coat composition in defined layers. Microscissors were used for seed coat fragment shape adjustment, microtweezers for sample holding and "microjackhammer" Milling Pro for precise mechanical removing of cell layers in defined depths (2, 5 or 10μm). These procedures circumvent the application of embedding media or enzymatic digestion of seed coat that would complicate mass spectra interpretation (presence of matrix signals, analyte signals enhancement or attenuation) and represent alternative for 3D metabolites profiling. In addition, microinjector was used to apply a solution on intact or micropeeled seed coat surface in nano-volumes, i.e. MALDI matrix and/or lithium salt, that provide improvement of signal of sugars. Utilization of EDM enabled optimization of matrix composition on a single small fragment of seed coat overcoming thus problems with biological (seed to seed) variability. LDI-MS data were studied by multivariate statistical analysis and significant metabolites in particular layers of seed coats were identified. Normalized intensities of signals (NS) of long-chain hydroxylated fatty acids (HLFA) on intact dormant pea genotype (JI64) seed coats were significantly higher than in their counterparts treated by micropeeling confirming HLFA accumulation in outermost layers (cutin). Fatty acids distribution differences between dormant and non-dormant genotypes were explored in detail. On the other hand, NS of sugar chains and particular polyphenols were significantly higher in micropeeled seed coats of studied dormant and non-dormant genotypes than in intact seed coats. Furthermore, combination of EDM with mass spectrometry imaging (MSI) allowed vertical profiling of metabolites in hilum (a place of former attachment of seed to maternal plant) and comparison of its composition with surrounding tissues. The obtained results contribute to the understanding of relations between seed coat chemical composition and physical seed dormancy.

Genome-wide association studies of mineral and phytic acid concentrations in pea (Pisum sativum L.) to evaluate biofortification potential.

Pea (Pisum sativum L.) is an important cool season food legume for sustainable food production and human nutrition due to its nitrogen fixation capabilities and nutrient-dense seed. However, minimal breeding research has been conducted to improve the nutritional quality of the seed for biofortification, and most genomic-assisted breeding studies utilize small populations with few single nucleotide polymorphisms (SNPs). Genomic resources for pea have lagged behind those of other grain crops, but the recent release of the Pea Single Plant Plus Collection (PSPPC) and the pea reference genome provide new tools to study nutritional traits for biofortification. Calcium, phosphorus, potassium, iron, zinc, and phytic acid concentrations were measured in a study population of 299 different accessions grown under greenhouse conditions. Broad phenotypic variation was detected for all parameters except phytic acid. Calcium exhibited moderate broad-sense heritability (H2) estimates, at 50%, while all other minerals exhibited low heritability. Of the accessions used, 267 were previously genotyped in the PSPPC release by the USDA, and we mapped the genotyping data to the pea reference genome for the first time. This study generated 54,344 high-quality SNPs used to investigate the population structure of the PSPPC and perform a genome-wide association study to identify genomic loci associated with mineral concentrations in mature pea seed. Overall, we were able to identify multiple significant SNPs and candidate genes for iron, phosphorus, and zinc. These results can be used for genetic improvement in pea for nutritional traits and biofortification, and the candidate genes provide insight into mineral metabolism.

Does Protein Glycation Impact on the Drought-Related Changes in Metabolism and Nutritional Properties of Mature Pea (Pisum sativum L.) Seeds?

Protein glycation is usually referred to as an array of non-enzymatic post-translational modifications formed by reducing sugars and carbonyl products of their degradation. The resulting advanced glycation end products (AGEs) represent a heterogeneous group of covalent adducts, known for their pro-inflammatory effects in mammals, and impacting on pathogenesis of metabolic diseases and ageing. In plants, AGEs are the markers of tissue ageing and response to environmental stressors, the most prominent of which is drought. Although water deficit enhances protein glycation in leaves, its effect on seed glycation profiles is still unknown. Moreover, the effect of drought on biological activities of seed protein in mammalian systems is still unstudied with respect to glycation. Therefore, here we address the effects of a short-term drought on the patterns of seed protein-bound AGEs and accompanying alterations in pro-inflammatory properties of seed protein in the context of seed metabolome dynamics. A short-term drought, simulated as polyethylene glycol-induced osmotic stress and applied at the stage of seed filling, resulted in the dramatic suppression of primary seed metabolism, although the secondary metabolome was minimally affected. This was accompanied with significant suppression of NF-kB activation in human SH-SY5Y neuroblastoma cells after a treatment with protein hydrolyzates, isolated from the mature seeds of drought-treated plants. This effect could not be attributed to formation of known AGEs. Most likely, the prospective anti-inflammatory effect of short-term drought is related to antioxidant effect of unknown secondary metabolite protein adducts, or down-regulation of unknown plant-specific AGEs due to suppression of energy metabolism during seed filling.

Effects of poly(vinylpyrrolidone) protected platinum nanoparticles on seed germination and growth performance of Pisum sativum

In this article, the effect of poly(vinylpyrrolidone) (PVP) stabilized platinum nanoparticles (Pt:PVP) on seed germination and growth performance of Pisum sativum (Pea) was investigated. Healthy mature Pea seeds were immersed for 1, 2 and 3 h into 1.0 mM concentrated Pt:PVP hydrosol and were sowed into soil. After immersing the seeds for 3 h into this solution, the germination rate decreased by 45% and the dormancy period increased from 2.5 days to 7 days. After 30 days of germination of saplings from seeds treated for 3 h, the root to shoot lengths were 20% less than the saplings from untreated seeds. 1 and 2 h of treatment did not have any significant impact on the germination rate, dormancy and plant growth. Arbuscular mycorrhizal fungi and rhizobial colonization in treated plants significantly decreased with soaking time prolongation. Arbuscular mycorrhizal fungi root colonization was significantly reduced in the plants from 3 h treated seeds group. The yield and biomass content of the produced plants were also calculated. For pea plants from seeds of the 3 h treatment group, the average number of seeds produced per plant increased by 163.5%, but the average seed weight decreased by 66.7%. Comparing with reported observations, it is inferred that either the modification of growth regulatory hormones or biochemicals associated with Pt:PVP during seed germination is responsible for such changes. 3.2 ± 0.8 nm Pt:PVP were prepared by high temperature ethanolic reduction of hexachloroplatinic acid solution containing PVP and were characterized by Transmission Electron Microscopy, X-ray Diffractometry and Ultraviolet–Visible Spectrophotometry.

Improved Protocol for Agrobacterium-Mediated Transformation of Pea (Pisum sativum)

Pea is one of the most important legume crops whose production is constantly threatened by field and storage pests and diseases. Developing insect resistant transgenic pea plants through Agrobacterium-mediated transformation is a promising solution to maintain crop yield. However, the transformation efficiency is still low. Therefore, there was an attempt to enhance transformation efficiency by optimizing infection time, co-cultivation period and in vitro regeneration system. Transformation was performed using segments of embryonic axes from mature pea seeds (Pisum sativum L. cv. Sponsor). The segments were inoculated with the hyper virulent EHA105 strain of Agrobacterium tumefaciens. The Agrobacterium strain harboured a binary vector pGII35S containing the bar gene which confers resistance to phosphinotricin. The selection medium contained P2 medium with increasing concentrations of phosphinothricin. To improve the regeneration efficiency, 4.5 μM zeatin was added to the selection medium. The highest transformation efficiency (7.89%) was achieved with infection time of 90 min and co-cultivation period of 2 days. The shoots elongated well and the number of shoots/explants was increased (6 folds) after addition of zeatin. Resistant shoots were grafted onto rootstocks in soil and grafting success rate was 100%. The integration of cry1Ac gene in T0 transgenic plants was confirmed primarily by Polymerase Chain Reaction and further analysed by Southern blotting.

Phenotyping: Using Machine Learning for Improved Pairwise Genotype Classification Based on Root Traits.

Phenotyping local crop cultivars is becoming more and more important, as they are an important genetic source for breeding – especially in regard to inherent root system architectures. Machine learning algorithms are promising tools to assist in the analysis of complex data sets; novel approaches are need to apply them on root phenotyping data of mature plants. A greenhouse experiment was conducted in large, sand-filled columns to differentiate 16 European Pisum sativum cultivars based on 36 manually derived root traits. Through combining random forest and support vector machine models, machine learning algorithms were successfully used for unbiased identification of most distinguishing root traits and subsequent pairwise cultivar differentiation. Up to 86% of pea cultivar pairs could be distinguished based on top five important root traits (Timp5) – Timp5 differed widely between cultivar pairs. Selecting top important root traits (Timp) provided a significant improved classification compared to using all available traits or randomly selected trait sets. The most frequent Timp of mature pea cultivars was total surface area of lateral roots originating from tap root segments at 0–5 cm depth. The high classification rate implies that culturing did not lead to a major loss of variability in root system architecture in the studied pea cultivars. Our results illustrate the potential of machine learning approaches for unbiased (root) trait selection and cultivar classification based on rather small, complex phenotypic data sets derived from pot experiments. Powerful statistical approaches are essential to make use of the increasing amount of (root) phenotyping information, integrating the complex trait sets describing crop cultivars.

Optimization the Work of Soil for the Cultivation of Afila Peas in Turda Area

By applying minimum tillage system are reduced degradation by erosion, increase organic matter, it restores the soil structure and through the introduction of legumes in rotation ensure a higher nitrogen quantity to crops which are in rotation. Research conducted at SCDA Turda in 2014 following the behavior of four varieties of afila peas in two soil tillage system (classical-with mould plow and with minimum tillage-the chisel variant) and the effect of tillage on the momentary and accessible water reserve from the soil. In the minimum tillage system with chisel obtained a very significant difference of production compared to the classic system (88g/m2) at green peas, and if mature pea beans the difference of -27 kg/ha obtained in variant with chisel being insignificant. Through the application of the minimum tillage system at pea get an important economy of 28.4% in terms of fuel costs (337.2 ron/ha) compared to the classic tillage system application (471 ron/ha). For producing a 1 ton peas in classical system is necessary to 21.9 l/t fuel consumption and fuel costs of 131.6 ron/t, higher than minimum tillage system were fuel consumption are 15.8 l/t with fuel costs of 94.9 ron/t.

Dissipation of pendimethalin in the soil of field pea (Pisum sativum L.) and detection of terminal residues in plants

Dissipation of pendimethalin in the soil of field peas (Pisum sativum L.) at 0 to 110 days, and terminal residues in green and mature pea were studied under field conditions. Pendimethalin was applied as pre-emergence herbicide at 750, to 185 g a.i. ha−1 in winter, in field peas. Dissipation of pendimethalin in the soil at 0 to 110 days followed first-order kinetics showing a half-life of 19.83 days averaged over all doses. Low pendimethalin residues were found in mature pea grain (0.004, 0.003, <0.001 μg g−1), and straw (0.007, 0.002, <0.001 μg g−1) at 750, 350 and 185 g a.i. ha−1 treatments, respectively. The study indicated that residues of pendimethalin in green and mature pea were within the prescribed MRL limits.

Temporal dynamics of nitrogen rhizodeposition in field pea as determined by 15N labeling

Arcand, M. M., Knight, J. D. and Farrell, R. E. 2013. Temporal dynamics of nitrogen rhizodeposition in field pea as determined by 15 N labeling. Can. J. Plant Sci. 93: 941–950. Assessing the contribution of symbiotically fixed N2 to soil from pulse crops necessitates a full accounting of the total crop residue N remaining in the field after seed harvest. Below-ground N, including root and rhizodeposit N, comprises an important component of this total plant N balance – without it the N input to soil is underestimated. Under controlled conditions in a greenhouse, N in intact roots and N rhizodeposition were quantified in field pea (Pisum sativum L.) using the cotton-wick 15N labeling technique. Plants were supplied with 15N on a continuous basis and harvested at the vegetative stage (nine leaves unfolded), flowering, and maturity. As the plants aged, the 15N enrichment in the rhizosphere soil decreased, whereas that in the bulk soil increased, suggesting that N released as root exudates comprised a more important proportion of N rhizodeposition in plants at the early vegetative stage compared with mature plants. In mature plants, N rhizodeposition was comprised predominantly of N associated with root turnover. The contribution of N rhizodeposition recovered in soil to the total plant N balance decreased from 17.8% at the vegetative stage harvest, to 12.3% at flowering, and finally to 7.5% at maturity. However, the total amount of root-derived N released to soil by pea increased with plant development. Below-ground N, including N rhizodeposition and N in intact roots contributed 11.3% to the total plant N balance of mature pea.

Vinyl sulfone silica: application of an open preactivated support to the study of transnitrosylation of plant proteins by S-nitrosoglutathione.

BackgroundS-nitrosylaton is implicated in the regulation of numerous signaling pathways with a diversity of regulatory roles. The high lability of the S-NO bond makes the study of proteins regulated by S-nitrosylation/denitrosylation a challenging task and most studies have focused on already S-nitrosylated proteins. We hypothesize that: i) S-nitrosoglutathione (GSNO) transnitrosylation is a feasible mechanism to account for the physiological S-nitrosylation of rather electropositive sulfur atoms from proteins, ii) affinity chromatography is a suitable approach to isolate proteins that are prone to undergo S-transnitrosylation and iii) vinyl sulfone silica is a suitable chromatographic bead.ResultsThe combination of vinyl sulfone silica with GSNO yielded an affinity resin that withstood high ionic strength without shrinking or deforming and that it was suitable to isolate potential GSNO transnitrosylation target candidates. Fractions eluted at 1500 mM NaCl resulted in a symmetrical peak for both, protein and S-nitrosothiols, supporting the idea of transnitrosylation by GSNO as a selective process that involves strong and specific interactions with the target protein. Proteomic analysis led to the identification of 22 physiological significant enzymes that differ with the tissue analyzed, being regulatory proteins the most abundant group in hypocotyls. The identification of chloroplastidic FBPase, proteasome, GTP-binding protein, heat shock Hsp70, syntaxin, catalase I, thioredoxin peroxidase and cytochrome P450 that have already been reported as S-nitrosylated by other techniques can be considered as internal positive controls that validate our experimental approach. An additional validation was provided by the prediction of the S-nitrosylation sites in 19 of the GSNO transnitrosylation target candidates.ConclusionsVinyl sulfone silica is an open immobilization support that can be turned ad hoc and in a straightforward manner into an affinity resin. Its potential in omic sciences was successfully put to test in the context of the analysis of post-translational modification by S-nitrosylation with two different tissues: mature pea leaves and embryogenic sunflower hypocotyls. The identified proteins reveal an intriguing overlap among S-nitrosylation and both tyrosine nitration and thioredoxin regulation. Chloroplastidic FBPase is a paradigm of such overlap of post-translational modifications since it is reversible modified by thioredoxin and S-nitrosylation and irreversibly by tyrosine nitration. Our results suggest a complex interrelation among different modulation mechanisms mediated by NO-derived molecules.

The plastid outer envelope protein OEP16 affects metabolic fluxes during ABA-controlled seed development and germination.

Previously, the OEP16.1 channel pore in the outer envelope membrane of mature pea (Pisum sativum) chloroplasts in vitro has been characterized to be selective for amino acids. Isolation of OEP16.2, a second OEP16 isoform from pea, in the current study allowed membrane localization and gene expression of OEP16 to be followed throughout seed development and germination of Arabidopsis thaliana and P. sativum. Thereby it can be shown on the transcript and protein level that the isoforms OEP16.1 and OEP16.2 in both plant species are alternating: whereas OEP16.1 is prominent in early embryo development and first leaves of the growing plantlet, OEP16.2 dominates in late seed development stages, which are associated with dormancy and desiccation, as well as early germination events. Further, OEP16.2 expression in seeds is under control of the phytohormone abscisic acid (ABA), leading to an ABA-hypersensitive phenotype of germinating oep16 knockout mutants. In consequence, the loss of OEP16 causes metabolic imbalance, in particular that of amino acids during seed development and early germination. It is thus concluded that in vivo OEP16 most probably functions in shuttling amino acids across the outer envelope of seed plastids.

Gibberellin Metabolism and Transport During Germination and Young Seedling Growth of Pea (Pisum sativum L.)

The role of gibberellins (GAs) during germination and early seedling growth is examined by following the metabolism and transport of radiolabeled GAs in cotyledon, shoot, and root tissues of pea (Pisum sativum L.) using an aseptic culture system. Mature pea seeds have significant endogenous GA20 levels that fall during germination and early seedling growth, a period when the seedling develops the capacity to transport GA20 from the cotyledon to the shoot and root of the seedling. Even though cotyledons at 0–2 days after imbibition have appreciable amounts of GA20, the cotyledons retain the ability to metabolize labeled GA19 to GA20 and express significant levels of PsGA20ox2 message (which encodes a GA biosynthesis enzyme, GA 20-oxidase). The large pool of cotyledonary GA20 likely provides substrate for GA1 synthesis in the cotyledons during germination, as well as for shoots and roots during early seedling growth. The shoots and roots express GA metabolism genes (PsGA3ox genes which encode GA 3-oxidases for synthesis of bioactive GA1, and PsGA2ox genes which encode GA 2-oxidases for deactivation of GAs to GA29 and GA8), and they develop the capacity to metabolize GAs as necessary for seedling establishment. Auxins also show an interesting pattern during early seedling growth, with higher levels of 4-chloro-indole-3-acetic acid (4-Cl-IAA) in mature seeds and higher levels of indole-3-acetic acid (IAA) in young root and shoot tissues. This suggests a changing role for auxins during early seedling development.

Photosynthetic alterations of pea leaves infected systemically by pea enation mosaic virus: A coordinated decrease in efficiencies of CO(2) assimilation and photosystem II photochemistry.

We have investigated photosynthetic changes of fully expanded pea leaves infected systemically by pea enation mosaic virus (PEMV) that often attacks legumes particularly in northern temperate regions. Atypical compatible virus-host interaction was monitored during 40 post-inoculation days (dpi). Aninitial PEMV-induced decrease in photosynthetic CO(2) assimilation was detected at 15dpi, when the virus appeared in the measured leaves. This decrease was not induced by stomata closure and corresponded with a decrease in the efficiency of photosystem II photochemistry (Φ(PSII)). Despite of a slight impairment of oxygen evolution at this stage, PSII function was not primarily responsible for the decrease in Φ(PSII). Chlorophyll fluorescence imaging revealed that Φ(PSII) started to decrease from the leaf tip to the base. More pronounced symptoms of PEMV disease appeared at later stages, when a typical mosaic and enations appeared in the infected leaves and oxidative damage of cell membranes was detected. From 30dpi, a degradation of photosynthetic pigments accelerated, stomata were closing and corresponding pronounced decline in CO(2) assimilation was observed. A concomitant photoprotective responses, i.e. an increase in non-photochemical quenching and accumulation of de-epoxidized xanthophylls, were also detected. Interestingly, alternative electron sinks in chloroplasts were not stimulated by PEMV infection, which is in contradiction to earlier reports dealing with virus-induced plant stresses. The presented results show that the PEMV-induced alterations in mature pea leaves accelerated leaf senescence during which a decrease in Φ(PSII) took place in coordinated manner with an inhibition of CO(2) assimilation.

Understanding the role of H(2)O(2) during pea seed germination: a combined proteomic and hormone profiling approach.

In a previous publication, we showed that the treatment of pea seeds in the presence of hydrogen peroxide (H(2)O(2)) increased germination performance as well as seedling growth. To gain insight into the mechanisms responsible for this behaviour, we have analysed the effect of treating mature pea seeds in the presence of 20 mm H(2)O(2) on several oxidative features such as protein carbonylation, endogenous H(2)O(2) and lipid peroxidation levels. We report that H(2)O(2) treatment of the pea seeds increased their endogenous H(2)O(2) content and caused carbonylation of storage proteins and of several metabolic enzymes. Under the same conditions, we also monitored the expression of two MAPK genes known to be activated by H(2)O(2) in adult pea plants. The expression of one of them, PsMAPK2, largely increased upon pea seed imbibition in H(2)O(2) , whereas no change could be observed in expression of the other, PsMAPK3. The levels of several phytohormones such as 1-aminocyclopropane carboxylic acid, indole-3-acetic acid and zeatin appeared to correlate with the measured oxidative indicators and with the expression of PsMAPK2. Globally, our results suggest a key role of H(2)O(2) in the coordination of pea seed germination, acting as a priming factor that involves specific changes at the proteome, transcriptome and hormonal levels.

A PQL (protein quantity loci) analysis of mature pea seed proteins identifies loci determining seed protein composition.

Legume seeds are a major source of dietary proteins for humans and animals. Deciphering the genetic control of their accumulation is thus of primary significance towards their improvement. At first, we analysed the genetic variability of the pea seed proteome of three genotypes over 3 years of cultivation. This revealed that seed protein composition variability was under predominant genetic control, with as much as 60% of the spots varying quantitatively among the three genotypes. Then, by combining proteomic and quantitative trait loci (QTL) mapping approaches, we uncovered the genetic architecture of seed proteome variability. Protein quantity loci (PQL) were searched for 525 spots detected on 2-D gels obtained for 157 recombinant inbred lines. Most protein quantity loci mapped in clusters, suggesting that the accumulation of the major storage protein families was under the control of a limited number of loci. While convicilin accumulation was mainly under the control of cis-regulatory regions, vicilins and legumins were controlled by both cis- and trans-regulatory regions. Some loci controlled both seed protein composition and protein content and a locus on LGIIa appears to be a major regulator of protein composition and of protein in vitro digestibility.

Chromatographical analysis of Phenolic acids in different preparations of pea (Pisum sativum) and chickpea (Cicer arietinum)

Legumes represent one of the most important food components to cover the basic proteins and energy requirements for the health of human beings. The secondary metabolites of legumes reveal valuable medicinal properties. Among the secondary metabolites, phenolic acids have greater importance. Analysis of phenolic acids in pea (Pisum sativum) and three varieties of chickpea (Cicer arietinum) seeds and their different preparations consumed commonly in India was done through High Performances Liquid Chromatography (HPLC). In total nine phenolic acids, viz., ferulic, gallic, chlorogenic, O-coumaric, cinnamic, vanillic, caffeic, tannic acids and salicylic acid could be identified on the basis of their retention time with standard compounds and co-chromatography. Several preparations of seeds of both the legumes were made for the analysis of phenolic acids. Maximum amount of gallic and tannic acids was observed in dried mature pea seeds. Maximum caffeic acid was found in boiled mature seeds of pea while ferulic acid in immature pea seed extract in distilled water for 24 h while vanillic acid was found maximum in similar extract. Three varieties of chickpea were taken, viz., Kabuli, Radhey and Avarodhi. In chickpea maximum gallic acid was observed in seeds boiled in distilled water while maximum tannic acid was observed in seeds of Kabuli variety fried with salt. Maximum caffeic acid was observed in Radhey (chickpea) seeds soaked in distilled water for 24 h while ferulic and salicylic acids in dried Radhey seeds (crushed in 80% ethanol) and vanillic acid was found maximum in fried Kabuli variety of chickpea without salt. O-coumaric acid was observed maximum in Avarodhi (chickpea) seeds soaked in distilled water.

Pea Seed Lectin Folds and Oligomerizes via an Intermediate Not Represented in the Structural Hierarchy

Large oligomeric proteins are usually thought to fold and assemble hierarchically: Domains fold and coalesce to form the subunits, and folded subunits can then associate to form the multimeric structure. We have investigated the refolding pathway of the beta-sheet protein pea seed lectin using spectroscopic and hydrodynamic techniques. In vivo, it is proteolytically processed post-translationally, so that the single-domain subunits of the initial homodimer themselves become heterodimers of intertwined fragment polypeptide chains. Despite this complex topology, mature pea seed lectin reassembles with considerable efficiency at low total protein concentration (10 mug/mL) and low temperature (10 degrees C), albeit very slowly (t1/2 approximately 2 days). Contrary to expectations, the primary assembly product is not the intact beta-sheet domain, but the larger fragment chains first dimerize to form the native-like subunit interface. The smaller fragment chains then associate with this preformed dimer.

Dynamics of C, N, P and microbial community composition in particulate soil organic matter during residue decomposition

Decomposing residues can be an important source of nutrients for plants, especially of N and P, but the relationship between N and P release and microbial community dynamics have rarely been studied. Two pea (Pisum sativum L.) residues with contrasting chemical composition, shoots from flowering pea (Pea-Y) with 2.9 mg P and 36 mg N kg−1 and from mature pea (Pea-M) with 0.3 mg P and 13 mg N kg−1, were added at a rate of 20 g kg soil−1 to a sandy soil low in nutrients. Particulate organic matter (POM) was isolated on days (d) 0, 5, 15, 28, 42 and 61 after residue addition and analysed for C, N, P and microbial community structure (fatty acid methyl ester analysis). The recovery of POM from residue-amended soils decreased over time to 30–40% of added amounts for both residues. Apart from d 0, the N concentration in POM was lower in residue-amended soil than in the control. Due to a rapid decrease in P concentration during the first 5 days in Pea-Y and a slow increase over the whole experiment in Pea-M, P concentrations in POM on d 61 were similar in all treatments. In Pea-Y, the dynamics of C, N and P were coupled, with amounts of C, N and P decreasing during the first 15 days and remaining stable thereafter. In Pea-M, a steady loss of C from POM was contrasted by a slight increase in P. As a result, the C/P ratio decreased from 1,330 on d 0 to 390 on d 61. The C/N ratio of Pea-M decreased only during the second phase of decomposition. The different nutrient dynamics in Pea-Y and Pea-M led to similar amounts of N and P in POM towards the end of the incubation. Microbial community composition in the POM in Pea-Y and Pea-M remained distinct from the control, even though it changed over time. POM was shown to be an important source of potentially available nutrients after addition of plant residues. In the unamended soil, stable nutrient amounts in POM suggested very low net nutrient release from native POM compared to POM after residue addition.

Effect of the stage of growth, wilting and inoculation in field pea (Pisum sativum L.) silages, III. Changes in the herbage and silage protein profiles

AbstractBACKGROUND: The effects of stage of growth, field wilting and inoculation with lactic acid bacteria (LAB) on the protein profile of herbage and silage were studied on field peas (Pisum sativum L.) harvested at four progressive morphological stages (end of flowering, I; beginning of pod filling, II; advanced pod filling, III; beginning of ripening, IV). The herbage was field wilted to a dry matter (DM) content around 330 g kg−1, for each stage of growth. The unwilted and wilted herbages were ensiled with (I) and without (C) a LAB inoculant.RESULTS: As a result of the advancing maturity of the crop, the main protein component was Rubisco in the early stages and seed storage proteins in the more advanced stages, due to the redistribution of organic nitrogen during seed filling. Extensive degradation of Rubisco occurred in all the silages, without any effect of inoculation or wilting. A good preservation of the proteins was observed in stage IV for both unwilted and wilted silages, without further protein preservation due to LAB inoculation.CONCLUSION: Protein protection observed in the more mature pea silage was due to the protein type and its localization and not to the level of DM at ensiling or to the inoculation. Copyright © 2007 Society of Chemical Industry