فصلنامه ژنتیک نوین
سال چهارم شماره 1 (پیاپی 16، بهار 1388)

Retrotransposons are mobile genetic elements that transpose through reverse transcription of an RNA intermediate. Retrotransposons are ubiquitous in plants and play a major role in plant gene and genome evolution. In the maize 50-80 % and in the wheat 90 % of the genome made up retrotransposons.It is believed that retrotransposons originated at the beginning of the transition from a putative RNA-based cellular genome to the DNA-based genome. The ubiquity of plant retrotransposons and their extreme sequence heterogeneity suggests that they were present in the first plants. Alternatively, retrotransposons may have originated after the creation of the first eukaryotes, and have reached their current wide dispersal by a combination of vertical and horizontal transmission.

Rerotransposons are the most abundant and widespread mobile genetic elements of eukaryotic genomes. Use of retrotransposons as molecular markers will be ideal regarding to their dispersion, ubiquity and prevalence in plant genomes. In order to developing retrotranpososns as molecular markers in wheat, 30 different retrotransposon families, previously detected in wheat and other plants evolutionary close to wheat, such as barley, oat, rice, maize and brachypodium were evaluated in wheat. All barley, oat and brachypodium retrotransposon based primers and most of rice and maize retrotransposon based primers amplified resoluble and scorable banding patterns in wheat. Rerotransposns Bare-1/Wis2-1A (wheat), Frodo TRIM (barley), oat LTRs, Sukkula (barley), Bagy2/Wilma (wheat), Daniela (wheat), Fatima (wheat) and Cerebera (barley) were active in wheat. Most primers designed based on conserved regions of retrotranpososn sequences, especially terminal regions of LTRs generated resoluble banding patterns. Desirable banding patterns produced by single and combinations of different retrotransposn primers demonstrating that the studied retrotransposon families are located in wheat genome in usual and nested status. Also, desirable banding patterns generated by single primer of 5' or 3' regions of LTR and primer combinations of 5' and 3' regions of different retrotransposon families in IRAP reactions implied head to head, tail to tail and head to tail situations of retrotranposons in wheat genome. Regarding to the results of this study, it is suggested to apply retrotranposon based molecular markers for genetic diversity, mapping and tagging of genes and traits in wheat and other crops.

In the present work expression of 61 candidate genes which are induced by salinity stress in mahooti and Chinese spring cultivars were evaluated and compared under 0 and 250 mM NaCl. In order to the study of candidate genes expression after preparing PCR products for each gene, were blotted on the membrane and after that hybridization were performed using cDNA probes in nonstressed and stressed plants. By means of TotalLab software, darkness of spots on the x-ray film were quantified. Results indicated that positive and significant correlation between biological replication exists. From 61 candidate genes, 21 and 5 candidate genes significantly were upregulated in mahooti (34%) and Chinese spring (6%), respectively. Under salinity and non salinity stress 52 and 27 percent of studied candidate genes in mahooti respect to Chinese spring cultivar considerably had higher expression level, respectively. The greatest increase and decrease in expression ratio under salinity stress to control condition was observed in TVP and HKT1, in mahooti and Chinese spring cultivars, correspondingly. The results of this study show that the different pattern of gene expression can be associated with salinity tolerance in mahooti cultivar.

Caspian Roach Rutilus rutilus caspicus is regarded as a valuable fish species for commercial food in the Caspian Sea. Genetic diversity of this fish species collected from two geographical areas (Gorgan Bay and Anzali Wetland) along the Iranian coastline of the Caspian Sea was examined by the analysis of RAPD markers. Using ten decamer primers, the total number of RAPD bands produced to both Gorgan Bay and Anzali Wetland populations were 94 bands. The percentages of polymorphic bands were comparable in Anzali wetland and Gorgan Bay, suggesting similar levels of polymorphism of the two populations. The value of genetic distance (0.04) among populations was small, despite the large geographic separation

Phenylketonuria (PKU) is the most prevalent disorder of amino acid metabolism. It is one of the most important preventable causes of mental retardation. Incidence of PKU in Iran has been estimated at 1 in 3627 births. The aim of this study is to assess the prevalence of PKU mutations in Iranian population. For this purpose, 150 unrelated patients with classic PKU (300 alleles) were screened for 10 mutations (IVS10-11g>a, R252W, R261X, R261Q, IVS11nt1, R408W, R408Q, L333F, 364delG and S67P) using polymerase chain reaction-restriction fragment length polymorphism. The predominant mutations in this population sample are IVS10-11g>a, R261Q, IVS11nt1g>c and R252W with the frequency 21.7%, 9%, 6.7% and 4.7% respectively. In addition, 6 other mutations have been identified at relatively low frequencies (R261X (4%), 364LdelG (3.7%), L333F (2%), R408W, R408Q and S67P (0.33%)). These informations provide a good basis for direct DNA diagnosis of PKU in this population.

The genotypes of hybrid rice with their parental lines were analyzed using microsatellite markers and some non-parental bands were observed in hybrid (heterozygous) individuals. These nonparental bands could be due to formation of heteroduplex DNA between allelic sequences. To test this hypothesis two source of DNA material were used. Firstly DNA template was formed by combining of equal amounts of parental DNA before performing of PCR. Secondly, the PCR products of this step were used as source materials of template mixing experiment by combining of equal amounts of PCR products of parental lines. The results confirmed the formation of the extra bands in heterozygous individuals, and proven that these art-factorials are consequences of formation hetroduplex between allelic sequences. Heteroduplexes are double strand DNA that formed from two different alleles by mismatches. These bands can be detected in specific position on gel due to their different migrating rate compared to corresponding homoduplexes. In the present study, it was evident that heteroduplex bands can be diagnostic feature for identify heterozygote individuals from homozygote ones. Accordingly, heteroduplex bands derived from RM1 and RM171 microsatellite markers were used for identifying and genetic purity testing of hybrid rice genotypes. Overall, it is revealed that heteroduplex bands not only beneficial in fingerprinting hybrids rice, but also useful for detecting the off type seeds in the rice hybrids

Late blight is the most important and destructive potato fungi-like pathogen in the world and is one of the major diseases on this crop in Iran. So, many researches have been done in the world to find pathogenesis mechanisms but there is a few in Iran. R-gene identification using effector genomics or effectoromics is one of the novel modern techniques. Effectors are pathogen molecules that manipulate host cell structure and function thereby facilitating infection and triggering defense responses such as HR. Profiling R-Avr interactions can lead to significant process in acquiring genetic resistance against the most destructive potato pathogen, namely late blight. Assessment of effector genes collection that are available by using computational methods from the pathogen in three important differential sets, Ma R5, Ma R8, Ma R9 from S.demissum was done. To identify functional candidate genes responses to the set of pGR106-effectors tested by PVX Agroinfection. Based on the results, Ma. R5 and Ma. R9 are containing R2-like genes and Ma. R8 contain R3a. This study shows, effectoromics as a promising novel technique to find new candidate resistance gene