نشریه زیست فناوری دانشگاه تربیت مدرس
سال پنجم شماره 2 (پیاپی 8، پاییز و زمستان 1393)

Laccase (benzenediol: oxygen oxidoreductase)، is a multicopper polyphenol oxidase enzyme which has glycoprotein structure. The Researches are indicated that laccase enzyme can play role in detoxification of aromatic pollutants (as petroleum derivatives) and conversion them to less toxic compounds. On the other hand، because of its extensive، fibrous root system; Festuca arundinacea، creates an appropriate environment that causes increased catalysis of petroleum contaminants. Considering the fact that increasing in catalysis of pollutants can be provided by presence and changes in activity of various plant enzymes، in this research; the changes in laccase activity of Festuca''s vegetative organs under soil pollution with different concentration of diesel fuel has been investigated. For this purpose، at first، the seeds of Festuca were cultivated in pots containing diesel fuel polluted soils and also control pots in greenhouse conditions. Then in specified time treatments، plants were harvested and plant extract containing laccase were extracted from aerial parts and roots of the plant، separately. After doing centrifuge، changes in enzyme activity were calculated by spectrophotometer. The results show that creation of soil pollution treatments compared with control samples، leads to increase in laccase activity in many cases. In other words، by increasing in laccase activity، the plant will increase its potency of decomposition and assimilation of pollutant hydrocarbons.

One of the most important proteins in gene silencing and creation of small RNA، are argonaute proteins. Most of these proteins have an endonucleolytic activity so argonaute proteins play a key role in creation of defense mechanism against certain pathogenic viruses. In current study we studied the putative argonaute genes in six medicinal plants using bioinformatic tools. Sequences of argonaute genes of six medicinal plants were retrieved from target database using Arabidopsis Argonaut blast. Sequence alignment، 3D structure، phylogenetic tree and conserved domain were generated for six medicinal plants argonautes. Results showed that studied medicinal plants have 6 to 18 argonaute proteins in the genome. There were three classes of Argonaute proteins similar to that of Arabidopsis، and each varies in length from 846 to 1187 AA، with a average of 970 AA and 108 kDa. six medicinal plants argonaute proteins had PAZ، PIWI and MID conserved domains. Our results showed that six medicinal plants have three classes of argonautes، This indicates is that the conservation of argonaute proteins in different plants.

This study was conducted to evaluate genetic variation among 70 sunflower recombinant inbred lines (RIL) derived from the crosses PAC2 × RHA266 together with parents based on seed morphological traits by using a rectangular lattice design with two replications. Seed morphological such as kernel length، kernel width، kernel diameter، 100-kernel weight، percentage of hull، percentage of dehulled kernel and seed yield per plant was measured. Analysis of variance revealed significant differences among lines for the studied traits. The highest coefficient of phenotypic variation was observed for seed yield per plant (23. 42) and the lowest one was observed for percentage of dehulled kernel (1. 37). The highest heritability was observed for 100-kernel weight (0. 995) and kernel width (0. 990) and the lowest one was observed for the yield per plant (0. 521). The highest correlation coefficients were observed between kernel diameter and kernel width (0. 908). Principal component analysis reduced the seed characteristics traits to 2 components explaining 81% accumulative variance. By using Ward clustering method based on seed morphological traits the 72 studied sunflower lines were classified into six groups.

Self-incompatibility is one of the most important difficulties in almond production which dramatically reduces fruit set and makes orchard management difficult. Therefore، breeding almond to produce self-compatible genotypes is very important. In this study، identification and screening of 100 almond hybrids obtained from cross between Touno (male parent) and A200 (female parent) after the self pollination by PCR reaction with specific primers of SfF and SfR. PCR results confirmed the situation of self-compatible hybrids. In addition، it indicated that، frequencies of Sf، S1 and S9 were 64%، 54% and 72% respectively، among hybrids. Hybrids and their parents vegetative traits (tree height، crown diameter، canopy diameter، branch number، the highest branch، leaf fall، lad length and across petiole length and glad number) using randomized complete bloke design (RCBD) in triplicate was done. PCR results confirmed the situation of self-compatible hybrids. In addition، it indicated that، 50% of genotypes were realized as self-compatible and another 50% were self-incompatible. Also primary evaluating of morphological traits of hybrids and their parents showed that most measured characters of hybrids was ranked between parents at present research، identified Self-compatible hybrids had been identified that can be used in almond breeding programs particularly to development the monoculture orchards of almond.

Analysis of signed biological networks has been an interest of some researchers in recent years. We consider communities and balanced clusters as two structural patterns that may reveal different structures in the networks. Although biological networks tend to structural balance، this study clarifies adhesive communities in some transcriptional networks of ecoli and yeast differ from the balanced clusters and have significantly more negative links in their structure. This difference may be used as an index in categorizing various systems'' structure and function. Also we study the important role of the positive links between balanced clusters، even though the links between these clusters are mostly negative. Analyzing data of some Gene Regulatory Networks، shows that perturbing the genes located at these links، has a larger effect on the system and causes more distance from the initial equilibrium state. So، signed clustering and detecting the links between these clusters can be considered as an effective approach in detecting the functional units and the key components in the system. This can be useful in applications like gene targeting in drug synthesis.

β- Xylosidase from Selenomonas ruminantium (SXA) is one of the most important enzyme for the hydrolysis of cell wall hemicellulose. SXA has potential utility in industrial processes especially production of bioethanol from bagasse. However، this xylosidase lose activ ity drastically above 50 °C. Each monomer of this homotetramer has four free buried cysteine. It seems that cysteine 286 has no role in protein function. In this study، to investigate effects of free buried cysteine on protein thermal stability، Cys 286 was replaced with the same size amino acid، valine. The mutant and native protein have expressed in Pichia pastoris. Kinetic and thermostability parameters of mutant were compared with the wild type enzyme. While pH optimum، temperature profile and catalytic efficiency of recombinant mutant were be found similar to native enzyme، mutant showed about 65% increase in thermostability respect to the wild type at 55 ˚C. Our results showed that free thiol group of cysteine caused the destabilization. Moreover، hydrophobic side chain of valine could involve in a hydrophobic interaction to stabilize SXA. Elimination of a free cysteine enhanced thermal stability without changing the catalytic efficiency of the enzyme that could be very important for biotechnological applications.

Lovastatin is a potent agent for lowering cholesterol of blood. Since one of the main reasons of mortality in developing countries is cardiovascular disease، which is caused by precipitation of fatty acid (especially cholesterol) in blood vessels; therefore diets containing lovastatin may prevent this type of disease. In this study، Lovastatin، monacolin K or competitive inhibitor of the HMG-CoA reductase (operative enzyme for cholesterol synthesis) was produced by submerged fermentation using Monascus purpureus PTCC5303. Seven chemical and nutritional parameters including maltose، peptone، MgSO4. 7H2O، MnSO4. H2O، KH2PO4، thiamin and pH screened using Plackett Burman experimental design for monacolin production. Among different parameters، maltose and MgSO4. 7H2O showed significant effect on biomass and monacolin production. The concentration of these agents were optimized using response surface methodology for lovastatin production in the shaker flask. The optimized medium contained 26 g/L maltose، 5 g/L peptone، 0. 1 g/L MgSO4. 7H2O، MnSO4. H2O 0. 5 g/L، 4 g/L KH2PO4، Vitamin B1 0. 1 g/L and pH 7. After 10 days of fermentation in the shaker flask with 130 rpm agitation and 30 ºC، we achieved maximum lovastatin production which was 63 mg/l.