Development of mycorrhized vitroplants of Jatropha curcas L. at different rooting stages

In this work, we attempted to assess the effects of inoculation of arbuscular mycorrhizal fungus (AMF), Glomus clarum, on the survival and development of micropropagated Jatropha curcas plantlets at different rooting stages. Elongated shoots (average 3?cm) of J. curcas, maintained for 0, 14, or 21?days on rooting medium in the presence or absence of 1?mg?L^?1 indole-3-butyric acid (IBA), were transferred to a sand:soil:vermiculite (1:1/2:1) (v:v:v) substrate. At the time of transplantation, the plantlets were either inoculated or not inoculated with G. clarum that had been monoaxenically produced in Ri-transformed carrot roots. After a 2-week acclimatization period, 100?% of the plants kept for 0 or 14?days in rooting medium survived. However, those that remained for 21?days in rooting medium displayed post-acclimatization survival rates of 93 and 89?% for plants inoculated and non-inoculated with G. clarum, respectively. Colonization rates ranged from 70 to 93?%, and the stimulatory effects of AMF were evidenced by increased phosphorus uptake by plants and increases in all evaluated growth parameters, except plant height. Plants that were not subjected to the rooting stage showed growth similar to or higher than those subjected to the rooting stage, regardless of the addition of IBA. It can be concluded that stimulatory effects of mycorrhizal fungi were observed, and that the inoculation of J. curcas proved effective during the initial period of the acclimatization phase.     

Starch Granule Re-Structuring by Starch Branching Enzyme and Glucan Water Dikinase Modulation Affects Caryopsis Physiology and Metabolism

Starch is of fundamental importance for plant development and reproduction and its optimized molecular assembly is potentially necessary for correct starch metabolism. Re-structuring of starch granules in-planta can therefore potentially affect plant metabolism. Modulation of granule micro-structure was achieved by decreasing starch branching and increasing starch-bound phosphate content in the barley caryopsis starch by RNAi suppression of all three Starch Branching Enzyme (SBE) isoforms or overexpression of potato Glucan Water Dikinase (GWD). The resulting lines displayed Amylose-Only (AO) and Hyper-Phosphorylated (HP) starch chemotypes, respectively. We studied the influence of these alterations on primary metabolism, grain composition, starch structural features and starch granule morphology over caryopsis development at 10, 20 and 30 days after pollination (DAP) and at grain maturity. While HP showed relatively little effect, AO showed significant reduction in starch accumulation with re-direction to protein and β-glucan (BG) accumulation. Metabolite profiling indicated significantly higher sugar accumulation in AO, with re-partitioning of carbon to accumulate amino acids, and interestingly it also had high levels of some important stress-related metabolites and potentially protective metabolites, possibly to elude deleterious effects. Investigations on starch molecular structure revealed significant increase in starch phosphate and amylose content in HP and AO respectively with obvious differences in starch granule morphology at maturity. The results demonstrate that decreasing the storage starch branching resulted in metabolic adjustments and re-directions, tuning to evade deleterious effects on caryopsis physiology and plant performance while only little effect was evident by increasing starch-bound phosphate as a result of overexpressing GWD.     

Mutacins from Streptococcus mutans UA159 are active against multiple streptococcal species

Streptococcus mutans UA159, whose genome is completely sequenced, produces two nonlantibiotic mutacins, mutacin IV (encoded by nlmAB) and mutacin V (encoded by nlmC). In this study, we investigated the contribution of nlmA and nlmB to mutacin IV activity and demonstrated by performing genetic studies as well as by using semipurified molecules that, in contrast to a previous report, both of these genes are required for optimum mutacin IV activity. We also showed that mutacin IV is active against multiple Streptococcus species. In contrast, mutacin V displayed a narrower inhibitory range than mutacin IV. Our results suggest that mutacin IV and mutacin V may act synergistically to inhibit various organisms.     

Comparative analysis of antioxidant activity,toxicity, and mineral composition of kernel and pomace of apricot (Prunus armeniaca L.) grown in Balochistan,Pakistan

The present study aims to investigate some physical attributes, total phenolics content, total flavonoids content, mineral composition, bioluminescence toxicity assay and antioxidant activity in terms of DPPH, HPS, TAC and FRAP assays in the kernel and pomace samples of six apricot cultivars grown in Balochistan, Pakistan. TFC and TPC determined by the AlCl₃ and Folin-Ciocalteu assays in apricot kernel extracts of six cultivars varied from 1797.5 (Chagali) to 4778.9 (Badoghur) mg QUE/100 g DW and from 1750.0 (Chagali) to 5005.8 (Badoghur) mg GAE/100 g DW. Apricot kernels exhibited higher antioxidant activity than pomace; antioxidant activity in terms of IC₅₀ in kernels ranged from 24.88 to 98.61 μg/ml for DPPH, 334.84 to 516.63 μg/ml for HPS, from 22.02 to 110.80 μg/ml for TAC and from 96.27 to 163.35 μg/ml for FRAP. The apricot kernels showed higher TPC, TFC, bioluminescence toxicity to V. logei and antioxidant activity than the pomace. The correlation analysis demonstrated substantial contributions of polyphenols and flavonoids to antioxidant assays. The sample type was the leading factor affecting the amounts of K, Na, Ca, Fe, and Mn in the tested samples; mineral contents were higher in pomace than kernels. The highest inhibition to V. logei was found in the kernels of Badoghur (IC₅₀ = 1.61 mg/ml). The PCA analysis showed significant contributions of phenolic and flavonoid contents towards antioxidant bioluminescence toxicity assays. Our results suggest Badoghur, Shakarpara and Sardai kernels are rich sources of secondary metabolites and possess remarkable antioxidant and antiluminescence activity and can make a significant contribution to the treatment and prevention of chronic health problems.     

Scaling of chew cycle duration in primates

The biomechanical determinants of the scaling of chew cycle duration are important components of models of primate feeding systems at all levels, from the neuromechanical to the ecological. Chew cycle durations were estimated in 35 species of primates and analyzed in conjunction with data on morphological variables of the feeding system estimating moment of inertia of the mandible and force production capacity of the chewing muscles. Data on scaling of primate chew cycle duration were compared with the predictions of simple pendulum and forced mass-spring system models of the feeding system. The gravity-driven pendulum model best predicts the observed cycle duration scaling but is rejected as biomechanically unrealistic. The forced mass-spring model predicts larger increases in chew cycle duration with size than observed, but provides reasonable predictions of cycle duration scaling. We hypothesize that intrinsic properties of the muscles predict spring-like behavior of the jaw elevator muscles during opening and fast close phases of the jaw cycle and that modulation of stiffness by the central nervous system leads to spring-like properties during the slow close/power stroke phase. Strepsirrhines show no predictable relationship between chew cycle duration and jaw length. Anthropoids have longer chew cycle durations than nonprimate mammals with similar mandible lengths, possibly due to their enlarged symphyses, which increase the moment of inertia of the mandible. Deviations from general scaling trends suggest that both scaling of the jaw muscles and the inertial properties of the mandible are important in determining the scaling of chew cycle duration in primates.     

An Extracelluar Protease,SepM, Generates Functional Competence-Stimulating Peptide in Streptococcus mutans UA159

Cell-cell communication in Gram-positive bacteria often depends on the production of extracellular peptides. The cariogenic bacterium Streptococcus mutans employs so-called competence-stimulating peptide (CSP) to stimulate mutacin (bacteriocin) production and competence development through the activation of the ComDE two-component pathway. In S. mutans, CSP is secreted as a 21-residue peptide; however, mass spectrometric analysis of culture supernatant indicates the presence of an 18-residue proteolytically cleaved species. In this study, using a transposon mutagenesis screening, we identified a cell surface protease that is involved in the processing of 21-residue CSP to generate the 18-residue CSP. We named this protease SepM for streptococcal extracellular protease required for mutacin production. We showed that the truncated 18-residue peptide is the biologically active form and that the specific postexport cleavage is a prerequisite to activate the ComDE two-component signal transduction pathway. We also showed that the CSP and the mutacins are exported outside the cell by the same ABC transporter, NlmTE. Our study further confirmed that the ComDE two-component system is absolutely necessary for mutacin production in S. mutans.     

Non‐GMO potato lines,synthesizing increased amylose and resistant starch,are mainly deficient in isoamylase debranching enzyme

Solanum tuberosum potato lines with high amylose content were generated by crossing with the wild potato species Solanum sandemanii followed by repeated backcrossing to Solanum tuberosum lines. The trait, termed increased amylose (IAm), was recessive and present after three generations of backcrossing into S. tuberosum lines (6.25% S. sandemanii genes). The tubers of these lines were small, elongated and irregular with small and misshaped starch granules and high sugar content. Additional backcrossing resulted in less irregular tuber morphology, increased starch content (4.3%–9.5%) and increased amylose content (29%–37.9%) but indifferent sugar content. The amylose in the IAm starch granules was mainly located in peripheral spots, and large cavities were found in the granules. Starch pasting was suppressed, and the digestion‐resistant starch (RS) content was increased. Comprehensive microarray polymer profiling (CoMPP) analysis revealed specific alterations of major pectic and glycoprotein cell wall components. This complex phenotype led us to search for candidate IAm genes exploiting its recessive trait. Hence, we sequenced genomic DNA of a pool of IAm lines, identified SNPs genome wide against the draft genome sequence of potato and searched for regions of decreased heterozygosity. Three regions, located on chromosomes 3, 7 and 10, respectively, displayed markedly less heterozygosity than average. The only credible starch metabolism‐related gene found in these regions encoded the isoamylase‐type debranching enzyme Stisa1. Decreased expression of mRNA (>500 fold) and reduced enzyme activity (virtually absent from IAm lines) supported Stisa1 as a candidate gene for IAm.     

SMU.152 acts as an immunity protein for mutacin IV

Streptococcus mutans, a principal causative agent of dental caries, secretes antimicrobial peptides known as mutacins to suppress the growth of competing species to establish a successful colonization. S. mutans UA159, a sequenced strain, produces at least two major mutacins, mutacins IV and V. Mutacin IV is a two-peptide mutacin encoded by nlmAB genes, which are mapped just upstream of a putative immunity-encoding gene SMU.152. Here we explored the function of SMU.152 as an immunity protein. We observed that overexpression of SMU.152 in two sensitive host strains converted the strains to become immune to mutacin IV. To identify the residues that are important for immunity function, we sequentially deleted residues from the C-terminal region of SMU.152. We observed that deletion of as few as seven amino acids, all of which are highly charged (KRRSKNK), drastically reduced the immunity function of the protein. Furthermore, we identified two other putative immunity proteins, SMU.1909 and SMU.925, which lack the last four charged residues (SKNK) that are present in SMU.152 but contain the KRR residues. Synthetic addition of SKNK residues to either SMU.1909 or SMU.925 to reconstitute the KRRSKNK motif and expressing these constructs in sensitive cells rendered the cells resistant to mutacin IV. We also demonstrated that deletion of Man-PTS system from a sensitive strain made the cells partially resistant to mutacin IV, indicating that the Man-PTS system plays a role in mutacin IV recognition.