The entomotoxin Jack Bean Urease changes cathepsin D activity in nymphs of the hematophagous insect Dipetalogaster maxima (Hemiptera: Reduviidae).

In insects, cathepsin D is a lysosomal aspartic endopeptidase involved in several functions such as digestion, defense and reproduction. Jack Bean Urease (JBU) is the most abundant urease isoform obtained from the seeds of the plant Canavalia ensiformis. JBU is a multifunctional protein with entomotoxic effects unrelated to its catalytic activity, by mechanisms not yet fully understood. In this work, we employed nymphs of the hematophagous insect Dipetalogaster maxima as an experimental model in order to study the effects of JBU on D. maxima CatD (DmCatD). In insects without treatment, immunofluorescence assays revealed a conspicuous distribution pattern of DmCatD in the anterior and posterior midgut as well as in the fat body and hemocytes. Western blot assays showed that the active form of DmCatD was present in the fat body, the anterior and posterior midgut; whereas the proenzyme was visualized in hemocytes and hemolymph. The transcript of DmCatD and its enzymatic activity was detected in the anterior and posterior midgut as well as in fat body and hemocytes. JBU injections induced a significant increase of DmCatD activity in the posterior midgut (at 3 h post-injection) whereas in the hemolymph, such an effect was observed after 18 h. These changes were not correlated with modifications in DmCatD mRNA and protein levels or changes in the immunofluorescence pattern. In vitro experiments might suggest a direct effect of the toxin in DmCatD activity. Our findings indicated that the tissue-specific increment of cathepsin D activity is a novel effect of JBU in insects.

GSK3-mediated stress signaling inhibits legume-rhizobium symbiosis by phosphorylating GmNSP1 in soybean.

Legumes establish symbiotic associations with rhizobia for biological nitrogen fixation. This process is highly regulated by various abiotic stresses, but the underlying genetic and molecular mechanisms remain largely unknown. In this study, we discovered that the glycogen synthase kinase 3 (GSK3)-like kinase, GmSK2-8, plays an important role in inhibiting symbiotic signaling and nodule formation in soybean (Glycine max) under salt stress. We found that GmSK2-8 is strongly induced in soybean under high-salt conditions, while GmSK2-8 could interact with two G. max Nodulation Signaling Pathway 1 (GmNSP1) proteins, GmNSP1a and GmNSP1b; these key transcription factors are essential for rhizobial infection, nodule initiation, and symbiotic gene expression in soybean. Furthermore, we demonstrated that GmSK2-8 phosphorylates the LHRI domain of GmNSP1a, inhibits its binding to the promoters of symbiotic genes, and thus suppresses nodule formation under salt stress. Knockdown of GmSK2-8 and its close homologs also resulted in reduced plant sensitivity to salt stress during nodule formation. Taken together, our findings indicate that GSK3-like kinases directly regulate the activities of GmNSP1s to mediate salt-inhibited legume-rhizobium symbiosis, providing novel targets for improving symbiotic nitrogen fixation under environmental stress conditions in soybean and possibly other legumes.

Synthesis of novel homoazanucleosides and their peptidyl analogs.

Synthesis of novel homoazanucleosides and their peptidyl analogs as hybrid molecules comprised of amino acids, an iminosugar and natural nucleobases is reported for the first time. A pluripotent amino-substituted chiral polyhydroxypyrrolidine, possessing orthogonally different functional groups on either arm of the pyrrolidine ring, served as an ideal substrate for the synthesis of the proposed peptidyl homoazanucleosides. The acid sensitive primary benzyloxy group, on one arm of the pyrrolidine ring, after selective deprotection, was utilized for the introduction of nucleobases to obtain the homoazanucleosides. The amino group on the other side offered the opportunity to be coupled with amino acids to deliver the desired peptidyl homoazanucleosides. Glycosidase inhibition studies revealed that the acetamido derivatives of homoazanucleosides were found to be sub-millimolar inhibitors of ß-N-acetyl-glucosaminidase.

Computational identification of receptor-like kinases "RLK" and receptor-like proteins "RLP" in legumes.

BACKGROUND: In plants, the plasma membrane is enclosed by the cell wall and anchors RLK and RLP proteins, which play a fundamental role in perception of developmental and environmental cues and are crucial in plant development and immunity. These plasma membrane receptors belong to large gene/protein families that are not easily classified computationally. This detailed analysis of these plasma membrane proteins brings a new source of information to the legume genetic, physiology and breeding research communities. RESULTS: A computational approach to identify and classify RLK and RLP proteins is presented. The strategy was evaluated using experimentally-validated RLK and RLP proteins and was determined to have a sensitivity of over 0.85, a specificity of 1.00, and a Matthews correlation coefficient of 0.91. The computational approach can be used to develop a detailed catalog of plasma membrane receptors (by type and domains) in several legume/crop species. The exclusive domains identified in legumes for RLKs are WaaY, APH Pkinase_C, LRR_2, and EGF, and for RLP are L-lectin LPRY and PAN_4. The RLK-nonRD and RLCK subclasses are also discovered by the methodology. In both classes, less than 20% of the total RLK predicted for each species belong to this class. Among the 10-species evaluated ~ 40% of the proteins in the kinome are RLKs. The exclusive legume domain combinations identified are B-Lectin/PR5K domains in G. max, M. truncatula, V. angularis, and V. unguiculata and a three-domain combination B-lectin/S-locus/WAK in C. cajan, M. truncatula, P. vulgaris, V. angularis. and V. unguiculata. CONCLUSIONS: The analysis suggests that about 2% of the proteins of each genome belong to the RLK family and less than 1% belong to RLP family. Domain diversity combinations are greater for RLKs compared with the RLP proteins and LRR domains, and the dual domain combination LRR/Malectin were the most frequent domain for both groups of plasma membrane receptors among legume and non-legume species. Legumes exclusively show Pkinase extracellular domains, and atypical domain combinations in RLK and RLP compared with the non-legumes evaluated. The computational logic approach is statistically well supported and can be used with the proteomes of other plant species.

Biological Activities of Selected Plants and Detection of Bioactive Compounds from Ardisia elliptica Using UHPLC-Q-Exactive Orbitrap Mass Spectrometry.

Plants and plant-based products have been used for a long time for medicinal purposes. This study aimed to determine the antioxidant and anti-α-glucosidase activities of eight selected underutilized plants in Malaysia: Leucaena leucocephala, Muntingia calabura, Spondias dulcis, Annona squamosa, Ardisia elliptica, Cynometra cauliflora, Ficus auriculata, and Averrhoa bilimbi. This study showed that the 70% ethanolic extract of all plants exhibited total phenolic content (TPC) ranging from 51 to 344 mg gallic acid equivalent (GAE)/g dry weight. A. elliptica showed strong 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide (NO) scavenging activities, with half maximal inhibitory concentration (IC50) values of 2.17 and 49.43 µg/mL, respectively. Most of the tested plant extracts showed higher inhibition of α-glucosidase enzyme activity than the standard, quercetin, particularly A. elliptica, F. auriculata, and M. calabura extracts with IC50 values of 0.29, 0.36, and 0.51 µg/mL, respectively. A total of 62 metabolites including flavonoids, triterpenoids, benzoquinones, and fatty acids were tentatively identified in the most active plant, i.e., A. elliptica leaf extract, by using ultra-high-performance liquid chromatography (UHPLC)-electrospray ionization (ESI) Orbitrap MS. This study suggests a potential natural source of antioxidant and α-glucosidase inhibitors from A. elliptica.

Improvement of growth performance of Amorpha fruticosa under contrasting regime of water and fertilizer in coal-contaminated spoils using response surface methodology.

BACKGROUND: Water availability and nutrient-status of soils play crucial roles in seedling establishment and plant survival in coal-spoiled areas worldwide. Restoration of spoils pertains to the application of proper doses of nutrients and water, and selection of particular plant species for efficient revegetation. This study aimed at examining the potential effects of different combinations of soil-water and fertilizers (nitrogen, N and phosphorus, P) on morpho-physiological and biochemical attributes of Amorpha fruticosa grown in coal-mined spoils. Three factors five-level central-composite-design with optimization technique response surface methodology (rsm) was used to optimize water irrigation and fertilizer application strategies. RESULTS: Our results revealed a strong correlation between experimental data and predicted values developed from the rsm model. The best responses of A. fruticosa in terms of plant height, stem diameter, root length, and dry biomass were observed under a high-water regime. Low-water regime caused a notable reduction in growth-associated parameters, and fertilization with either N or P did not show positive effects on those parameters, indicating that soil-water was the most influential factor for growth performance. Leaf water potential, gas-exchange parameters, and chlorophyll content significantly increased under high levels of soil-water, N and P, suggesting a synergistic effect of these factors for the improvement of photosynthesis-related parameters. At low soil-water contents and N-P fertilizer application levels, enhanced accumulation of malondialdehyde and proline indicated that A. fruticosa suffered from oxidative and osmotic stresses. Amorpha fruticosa also responded to oxidative stress by accelerating the activities of superoxide dismutase, catalase, and peroxidase. The effects of both fertilizers relied on soil-water, and fertilization was most effective under well-watered conditions. The maximum growth of A. fruticosa was observed under the combination of soil-water, N-dose and P-dose at 76% field capacity, 52.0 mg kg- 1 and 49.0 mg kg- 1, respectively. CONCLUSION: Our results demonstrate that rsm effectively designed appropriate doses of water and N-P fertilizer to restore coal-spoiled soils. Furthermore, A. fruticosa responded to low-water and fertilizer-shortage by upregulating defensive mechanism to avoid damage induced by such deficiencies. Finally, our findings provide effective strategies for revegetation of coal-contaminated spoils with A. fruticosa using appropriate doses of water and N-P fertilizers.

Reconstruction of the Evolutionary Histories of UGT Gene Superfamily in Legumes Clarifies the Functional Divergence of Duplicates in Specialized Metabolism.

Plant uridine 5'-diphosphate glycosyltransferases (UGTs) influence the physiochemical properties of several classes of specialized metabolites including triterpenoids via glycosylation. To uncover the evolutionary past of UGTs of soyasaponins (a group of beneficial triterpene glycosides widespread among Leguminosae), the UGT gene superfamily in Medicago truncatula, Glycine max, Phaseolus vulgaris, Lotus japonicus, and Trifolium pratense genomes were systematically mined. A total of 834 nonredundant UGTs were identified and categorized into 98 putative orthologous loci (POLs) using tree-based and graph-based methods. Major key findings in this study were of, (i) 17 POLs represent potential catalysts for triterpene glycosylation in legumes, (ii) UGTs responsible for the addition of second (UGT73P2: galactosyltransferase and UGT73P10: arabinosyltransferase) and third (UGT91H4: rhamnosyltransferase and UGT91H9: glucosyltransferase) sugars of the C-3 sugar chain of soyasaponins were resulted from duplication events occurred before and after the hologalegina-millettoid split, respectively, and followed neofunctionalization in species-/ lineage-specific manner, and (iii) UGTs responsible for the C-22-O glycosylation of group A (arabinosyltransferase) and DDMP saponins (DDMPtransferase) and the second sugar of C-22 sugar chain of group A saponins (UGT73F2: glucosyltransferase) may all share a common ancestor. Our findings showed a way to trace the evolutionary history of UGTs involved in specialized metabolism.

Improved protease activity of Pixian broad bean paste with cocultivation of Aspergillus oryzae QM-6 and Aspergillus niger QH-3

BACKGROUND: The preparation of broad bean koji is a key process in the production of Pixian broad bean paste (PBP). Protease is essential for the degradation of proteins during PBP fermentation. To obtain broad bean koji with high protease activity using the cocultivated strains of Aspergillus oryzae QM-6 (A. oryzae QM-6) and Aspergillus niger QH-3 (A. niger QH-3), the optimization of acid and neutral protease activities was carried out using Box­Behnken design with response surface methodology (RSM). RESULTS: The optimum conditions were found to be as follows: inoculation proportion (X1), 3:1 (A. oryzae QM-6: A. niger QH-3, w/w); culture temperature (X2), 33°C; inoculum size (X3), 0.5% (w/w); incubation time (X4), 5 d. The acid and neutral protease activities were 605.2 ± 12.4 U/g and 1582.9 ± 23.7 U/g, respectively, which were in good agreement with the predicted values. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles revealed that the broad bean koji extracellular proteins in the case of cocultivation were richer compared to those in the case of A. oryzae QM-6 or A. niger QH-3 strain only. In addition, the free amino acids (FAAs) in the fermentation product were 55% higher in the cocultivation process than in that involving only A. oryzae QM-6, further confirming the diversity of proteases in the fermentation products. CONCLUSIONS: The optimal conditions of koji-making in PBP were obtained using RSM. The cocultivation of A. oryzae and A. niger increases the overall enzyme activities in the culture medium and the FAAs content, which would thus have potential application in the PBP industry.

Expression of galactinol synthase from Ammopiptanthus nanus in tomato improves tolerance to cold stress.

Soluble carbohydrates not only directly affect plant growth and development but also act as signal molecules in processes that enhance tolerance to cold stress. Raffinose family oligosaccharides (RFOs) are an example and play an important role in abiotic stress tolerance. This study aimed to determine whether galactinol, a key limiting factor in RFO biosynthesis, functions as a signal molecule in triggering cold tolerance. Exposure to low temperatures induces the expression of galactinol synthase (AnGolS1) in Ammopiptanthus nanus, a desert plant that survives temperatures between -30 °C to 47 °C. AnGolS1 has a greater catalytic activity than tomato galactinol synthase (SlGolS2). Moreover, SlGolS2 is expressed only at low levels. Expression of AnGolS1 in tomato enhanced cold tolerance and led to changes in the sugar composition of the seeds and seedlings. AnGolS1 transgenic tomato lines exhibited an enhanced capacity for ethylene (ET) signaling. The application of galactinol abolished the repression of the ET signaling pathway by 1-methylcyclopropene during seed germination. In addition, the expression of ERF transcription factors was increased. Galactinol may therefore act as a signal molecule affecting the ET pathway.

Acaciain peptidase: The first South American pollen peptidase potentially involved in respiratory allergy.

Acacia caven (Mol.) Molina pollen causes pollinosis in South America. The aim of this work was to isolate, purify, and characterize the proteolytic enzymes of A. caven pollen, and study their influence on allergy. A series of chromatographic steps were applied to purify the proteolytic extract of A. caven pollen. The purified fraction was partially characterized, and then it was assayed on airway bioactive peptides (substance P, vasoactive intestinal peptide, and bradykinin), and peptide degradation was visualized by direct protein sequencing. The cellular detachment of an airway-derived epithelial cell line (A-549) was measured by methylene blue binding assay. The degradation of proteins from intercellular junctions (occludin, claudin, and E-cadherin) was visualized by Western blot. A 75-kDa peptidase, named acaciain peptidase, was purified and classified as a serine peptidase. Acaciain peptidase degraded bioactive peptides involved in the maintenance and recovery of the bronchomotor tone; it caused cellular detachment of A-549 cell line, and degradation of intercellular junction proteins. Acaciain peptidase can alter the integrity of the epithelium barrier, causing cell permeability, increasing the allergic sensitization and exacerbating the overall bronchoconstrictive effect detected in asthmatic lungs. This novel serine peptidase constitutes a relevant therapeutic target in the treatment of allergic disorders.

Glutamate dehydrogenase is essential in the acclimation of Virgilia divaricata, a legume indigenous to the nutrient-poor Mediterranean-type ecosystems of the Cape Fynbos.

Glutamate dehydrogenase (NAD(H)- GDH, EC 1.4.1.2) is an important enzyme in nitrogen (N) metabolism. It serves as a link between C and N metabolism, in its role of assimilating ammonia into glutamine or deaminating glutamate into 2-oxoglutarate and ammonia. GDH may also have a key in the N assimilation of legumes growing in P-poor soils. Virgilia divaricata is such a legume, growing in the nutrient limited soils of the mediterranean-type Cape fynbos ecosystem. In order to understand the role of GDH in the nitrogen nutrition of V. divaricata, the aim of this study was to identify the GDH gene transcripts, their relative expressions and enzyme activity in P-stressed roots and nodules during N metabolism. During P deficiency there was a reduction in total plant biomass as well as total plant P concentration. The analysis of the GDH cDNA sequences in V. divaricata revealed the presence of GHD1 and GHD2 subunits, these corresponding to the GDH1, GDH-B and GDH3 genes of legumes and non-legume plants. The relative expression of GDH1 and GDH2 genes in the roots and nodules, indicates that two the subunits were differently regulated depending on the organ type, rather than P supply. Although both transcripts appeared to be ubiquitously expressed in the roots and nodules, the GDH2 transcript evidently predominated over those of GDH1. Furthermore, the higher expression of both GDH transcripts in the roots than nodules, suggests that roots are more reliant on on GDH in P-poor soils, than nodules. With regards to GHD activity, both aminating and deaminating GDH activities were differently affected by P deficiency in roots and nodules. This may function to assimilate N and regulate internal C and N in the roots and nodules. The variation in GDH1 and GDH2 transcript expression and GDH enzyme activities, indicate that the enzyme may be regulated by post-translational modification, instead of by gene expression during P deficiency in V. divaricata.

Functional characterization of DiMMS21, a SUMO ligase from Desmodium intortum.

SUMOylation is an important protein modification that regulates the properties of substrate proteins in a variety of cellular processes. SUMOylation is catalyzed via a cascade of enzymes and is usually stimulated by SUMO E3 ligases. However, the molecular functions and regulatory mechanisms of SUMOylation in forage crops are unknown. Here, we isolated and functionally characterized DiMMS21, a homolog of the Arabidopsis thaliana SUMO ligase AtMMS21, from the forage legume Desmodium intortum. DiMMS21 is expressed ubiquitously in various D. intortum organs and its encoded protein is found in the cytoplasm and nucleus. Bioinformatics analysis indicated that DiMMS21 contains a conserved SP-RING domain that is required for its activity. Biochemical evidence supports the notion that this protein is a functional SUMO ligase. When expressed in an Arabidopsis mms21 mutant, DiMMS21 completely rescued the defects in root, leaf, and silique development. The results from cotyledon greening and marker gene expression suggested that DiMMS21 can only partially complements the role of AtMMS21 in abscisic acid (ABA) responses. In summary, we characterized the molecular features of DiMMS21 and uncovered potential roles of this SUMO ligase in development and ABA responses, increasing our understanding on the function of SUMOylation in forage crops.

Recombinant Butelase-Mediated Cyclization of the p53-Binding Domain of the Oncoprotein MdmX-Stabilized Protein Conformation as a Promising Model for Structural Investigation.

Cyclization of the polypeptide backbone has proven to be a powerful strategy for enhancing protein stability for fundamental research and pharmaceutical application. The use of such an approach is restricted by how well a targeted polypeptide can be efficiently ligated. Recently, an Asx-specific peptide ligase identified from a tropical cyclotide-producing plant and named butelase 1 exhibited excellent cyclization kinetics that cannot be matched by other known ligases, including intein, PATG, PCY1, and sortase A. In this work, we aimed to examine whether butelase 1 facilitated protein conformational stability for structural investigation. First, we successfully expressed recombinant butelase 1 (rBTase) in the yeast Pichia pastoris. Next, rBTase was shown to be highly efficient in the cyclization of the p53-binding domain (N-terminal domain) of murine double minute X (N-MdmX), an important target for designing anticancer drugs. The cyclized N-MdmX (cMdmX) exhibited increased conformational stability and improved interaction with the ligand compared with those of noncyclized N-MdmX. Importantly, the thermal melting process was completely reversible, contrary to noncyclized N-MdmX, and the melting temperature ( Tm) of cMdmX was increased to 47 from 43 °C. This stable conformation of cMdmX was further confirmed by 15N-1H heteronuclear single-quantum coherence nuclear magnetic resonance (NMR) spectroscopy. The complex of cMdmX and the ligand was tested for protein crystallization, and several promising findings were revealed. Therefore, our work not only provides a recombinant version of butelase 1 but also suggests a conventional approach for preparing stable protein samples for both protein crystallization and NMR structural investigation.

Tight-binding inhibition of jack bean α-mannosidase by glycoimidazole clusters.

The best multivalent effects observed in glycosidase inhibition have been achieved so far with jack bean α-mannosidase (JBα-man) using iminosugar clusters based on weakly binding mismatching active-site-directed inhibiting epitopes (inhitopes) in the d-gluco series. Here, we synthesize and evaluate as JBα-man inhibitors a series of mono- to 14-valent glycoimidazoles with inhitopes displaying inhibition values up to the range of hundreds of nMs to study the impact of inhitope affinity on the multivalent effect. The most potent inhibitor of the series, a 14-valent mannoimidazole derivative, inhibits JBα-man with a nanomolar Ki value (2 ± 0.5 nM) and binding enhancements observed are, at best, relatively small (up to 25-fold on a valency-corrected basis). The results of this study support the fact that JBα-man-inhitope affinity and the strength of the inhibitory multivalent effect evolve in the opposite direction. The major impact of the glycoimidazole-based inhitope is found on the binding scenario; most of the synthesized mannoimidazole clusters as well as a 14-valent glucoimidazole derivative prove to be tight binding inhibitors of JBα-man.

Recent advances in the development of legumain-selective chemical probes and peptide prodrugs.

Legumain, which is also known as vacuolar processing enzyme (VPE) or asparaginyl endopeptidase (AEP), is a cysteine protease that was first discovered and characterized in the leguminous seeds of the moth bean in the early 1990s. Later, this enzyme was also detected in higher organisms, including eukaryotes. This pH-dependent protease displays the highest activity in acidic endolysosomal compartments; however, legumain also displays nuclear, cytosolic and extracellular activity when stabilized by other proteins or intramolecular complexes. Based on the results from over 25 years of research, this protease is involved in multiple cellular events, including protein degradation and antigen presentation. Moreover, when dysregulated, this protease contributes to the progression of several diseases, with cancer being the well-studied example. Research on legumain biology was undoubtedly facilitated by the use of small molecule chemical tools. Therefore, in this review, I present the historical perspectives and most current strategies for the development of small molecule substrates, inhibitors and activity-based probes for legumain. These tools are of paramount importance in elucidating the roles of legumain in multiple biological processes. Finally, as this enzyme appears to be a promising molecular target for anticancer therapies, the development of legumain-activated prodrugs is also described.

Adevonin, a novel synthetic antimicrobial peptide designed from the Adenanthera pavonina trypsin inhibitor (ApTI) sequence.

The biological activities and the structural arrangement of adevonin, a novel antimicrobial peptide, were investigated. The trypsin inhibitor ApTI, isolated from Adenanthera pavonina seeds, was used as a template for screening 18-amino acid peptides with predicted antimicrobial activity. Adevonin presented antimicrobial activity and minimum inhibitory concentrations (MIC) ranging from 1.86 to 7.35 µM against both Gram-positive and - negative bacterial strains. Moreover, adevonin exerted time-kill effects within 10 min and both susceptible and drug-resistant bacterial strains were affected by the peptide. In vitro and in vivo assays showed that, at MIC concentration, adevonin did not affect human fibroblasts (MRC-5) viability or Galleria mellonella survival, respectively. Hemolytic activity was observed only at high peptide concentrations. Additionally, nucleic acid efflux assays, gentian violet uptake and time-kill kinetics indicate that the antimicrobial activity of adevonin may be mediated by bacterial membrane damage. Furthermore, molecular dynamic simulation in the presence of SDS micelles and anionic membrane bilayers showed that adevonin acquired a stable α-helix secondary structure. Further studies are encouraged to better understand the mechanism of action of adevonin, as well as to investigate the anti-infective activity of this peptide.

Synthesis of some novel quinazolin-4(3H)-one hybrid molecules as potent urease inhibitors.

A new series of quinazolinone hybrid molecules containing coumarin, furan, 1,2,4-triazole and 1,2,4-thiadiazole rings was designed, synthesized, and screened for their urease inhibition activities. All newly synthesized compounds showed outstanding urease inhibitory potentials with IC50 values ranging between 1.26 ± 0.07 and 7.35 ± 0.31 µg/mL. Among the series, coumarin derivatives (10a-d) exhibited the best inhibitory effect against urease in the range of IC50 = 1.26 ± 0.07 to 1.82 ± 0.10 µg/mL, when compared to standard urease inhibitors such as acetohydroxamic acid and thiourea (IC50 = 21.05 ± 0.96 and 15.08 ± 0.71 µg/mL, respectively). Molecular docking studies were also performed to analyze the binding mode of compound 10b, and supported the experimental results.

A root-associated purple acid phosphatase, SgPAP23, mediates extracellular phytate-P utilization in Stylosanthes guianensis.

As a major component of soil organic phosphorus (P), phytate-P is unavailable to plants unless hydrolysed by phytase to release inorganic phosphate. However, knowledge on natural variation in root-associated phytase activity and its underlying molecular mechanisms in plants remains fragmentary. In this study, variations in root internal and associated phytase activity were observed among 39 genotypes of Stylosanthes guianensis (Stylo), which is well adapted to acid soils. Furthermore, TPRC2001-1, the genotype with the highest root-associated phytase activity, was more capable of utilizing extracellular phytate-P than Fine-stem, the genotype with the lowest root-associated phytase activity. After protein liquid chromatography-tandem mass spectrometry analysis, a purple acid phosphatase (PAP), SgPAP23, was identified and cloned from TPRC2001-1. SgPAP23 exhibited high activity against phytate-P and was mainly localized on the plasma membrane. Furthermore, SgPAP23 overexpression resulted in significant increases of root-associated phytase activity and thus facilitated extracellular phytate-P utilization in both bean (Phaseolus vulgaris) hairy roots and Arabidopsis thaliana. The results herein support the conclusion that SgPAP23 is a primary contributor to the superior extracellular phytate-P utilization in stylo and thus is used to develop cultivars with efficient extracellular phytate-P utilization.

Molecular cloning and biotic elicitation response of phenylalanine ammonia-lyase gene of Astragalus chrysochlorus.

Phenylalanine ammonia lyase (PAL) is the first enzyme of the phenylpropanoid pathway, and it is necessary to upregulate flavonoid biosynthesis in most of the plant species. In this study, we have cloned PAL gene from endemic Astragalus chrysochlorus which is a producer of phenolic nicotiflorin (kaempferol-3-O-rutinoside). The cDNA encoding PAL was cloned from A. chrysochlorus using RT-PCR (reverse transcription-polymerase chain reaction) with conserved primer pairs. Amino acid sequence alignments showed that AcPAL (2160 bp, Accession number: KM189182) has more than 95% amino acid identity with their homologues in other Astragalus species. The coding sequence for the protein of AcPAL is 720 amino acids with a calculated molecular weight of 78.53 kDa. Full length AcPAL was cloned and expressed in Escherichia coli. qPCR (quantitative real-time PCR) analysis of the expression of PAL gene of A. chrysochlorus suggested that maximum transcript level was observed in 3 h yeast extract elicited suspension cells. Our findings suggest that AcPAL plays role in early response for yeast extract treatment. The isolation of AcPAL gene could be result in further studies for overproduction of secondary metabolite, nicotiflorin.

Cytosolic Cysteine Synthase Switch Cysteine and Mimosine Production in Leucaena leucocephala.

In higher plants, multiple copies of the cysteine synthase gene are present for cysteine biosynthesis. Some of these genes also have the potential to produce various kinds of ß-substitute alanine. In the present study, we cloned a 1275-bp cDNA for cytosolic O-acetylserine(thiol)lyase (cysteine synthase) (Cy-OASTL) from Leucaena leucocephala. The purified protein product showed a dual function of cysteine and mimosine synthesis. Kinetics studies showed pH optima of 7.5 and 8.0, while temperature optima of 40 and 35 °C, respectively, for cysteine and mimosine synthesis. The kinetic parameters such as apparent Km, kcat were determined for both cysteine and mimosine synthesis with substrates O-acetylserine (OAS) and Na2S or 3-hydroxy-4-pyridone (3H4P). From the in vitro results with the common substrate OAS, the apparent kcat for Cys production is over sixfold higher than mimosine synthesis and the apparent Km is 3.7 times lower, suggesting Cys synthesis is the favored pathway.