Reza Amiri

What happens in plant molecular responses to cold stress

Low temperature is one of the major abiotic stresses limiting the productivity and the geographical distribution of many important crops. Many plants increase in freezing tolerance in response to low temperatures. This phenomenon needs a vast reprogramming of gene expression which results in the adjusted metabolic-structural alterations. However, the efficient adjustments are dependent on proper cold signal transduction. The first stage is cold stress signal perception which is carried out by different pathways. Transcriptional cascades are next players which operate through ABA-dependent and ABA-independent pathways to induce cold-regulated (COR) gene expression and the result is increasing in the levels of hundreds of metabolites, which some of them are known to have protective effects against the damaging effects of cold stress and some like soluble sugars, reactive oxygen species and photosynthetic metabolites are thought to act as signaling molecules and regulate special COR genes. The different aspects of these events are discussed in detail below.

Change in membrane fatty acid compositions and cold-induced responses in chickpea

Plant cells often increase cold tolerance by reprogramming their genes expression which results in adjusted metabolic alternations, a process enhanced under cold acclimation (CA) phase. In present study, we assessed the changes of membrane fatty acid compositions and defense machine (like antioxidative enzymes) along with damage indexes like electrolyte leakage index (ELI) and malondialdehyde (MDA) during CA, cold stress (CS) and recovery (R) phases in chickpea (Cicer arietinum L.). Results showed an increase in unsaturated fatty acids ratio compare to saturated ones which is a sign of cold tolerance especially after CA phase. Antioxidant enzymes had an important role during CA and R phases while CS affected their activity which can be a sign for associating other metabolites or enzymes activities to create cold tolerance in plants. To investigation of enzymes assay under experimental treatments, the expression pattern of some enzymes including superoxide dismutase (sod), catalase (cat) and lipoxygenase (lox) was studied using quantitative real time PCR. LOX activity has shown a bilateral behavior: a positive relation with membrane damage index in CA and an interesting link with double bond index (DBI) in CS indicating probably its role in secondary metabolites like jasmonic acid signaling pathway. It was suggested that increased DBI and low LOX activity under CS could be a reason for plant cold tolerance.

Expression of Acyl-lipid Δ12-desaturase Gene in Prokaryotic and Eukaryotic Cells and Its Effect on Cold Stress Tolerance of Potato

We report the expression profile of acyl-lipid Delta12-desaturase (desA) gene from Synechocystis sp. PCC6803 and its effect on cell membrane lipid composition and cold tolerance in prokaryotic (Escherichia coli) and eukaryotic (Solanum tuberosum) cells. For this purpose, a hybrid of desA and reporter gene encoding thermostable lichenase (licBM3) was constructed and used to transform these cells. The expression of this hybrid gene was measured using qualitative (Petri dish test, electrophoregram and zymogram) and quantitative methods (spectrometry and gas liquid chromatography assays). The maximum level of linoleic acid in the bacterial cells containing hybrid gene was 1.9% of total fatty acids. Cold stress tolerance assays using plant damage index and growth parameters showed that cold tolerance was enhanced in primary transgenic lines because of increased unsaturated fatty acid concentration in their lipids. The greatest content of 18:2 and 18:3 fatty acids in primary transgenic plants was observed for lines 2 (73%) and 3 (41%). Finally, our results showed that desaturase could enhance tolerance to cold stress in potato, and desaturase and lichenase retain their functionality in the structure of the hybrid protein where the enzymatic activity of target gene product was higher than in the case of reporter lichenase gene absence in the construction.

A new RAPD marker for beet necrotic yellow vein virus resistance gene in Beta vulgaris

RAPD markers linked to beet necrotic yellow vein virus (BNYVV) resistance genes were identified in two Beta vulgaris accessions Holly-1-4 and WB42 using bulked segregant analysis. The polymorphism revealed by the RAPD markers in the F2 generations of WB42 was higher than that of Holly-1-4. The segregation distortion at marker loci was slightly lower in the B. vulgaris × B. maritima cross than in the B. vulgaris × B. vulgaris cross. For Holly-1-4, a RAPD marker was identified in a long distance from the resistance gene of Rz1. However, a RAPD marker tightly linked with Rz2 gene in repulsion phase was detected with an approximate distance of 0.036 rf. This marker was not generation specific and showed high repeatability. The distance between Rz1 and Rz2 genes was estimated as 0.464 rf. After the Rz2Rz2 and Rz2rz2 genotypes were identified using ELISA values and repulsion phase RAPD markers, comparison of their ELISA means revealed lack of the gene dosage effects. Nevertheless, under the field or severe infection conditions, the difference between ELISA mean values of the Rz2Rz2 and Rz2rz2 genotypes might be more than that observed in this study and the gene dosage effects of Rz2 allele might be important.

Genetic diversity of Iranian Bunium persicum germplasm by morphological markers and essential oil components

Medicinal and aromatic plants have a traditional history of use, with strong roles in cultural heritage, and in the appreciation of food and its links to health. Black caraway (Bunium persicum Boiss. Fedtsch) belonging to the family of Apiaceae, is an economically important medicinal and aromatic plant found naturally growing in dry temperate regions of Iran and some other areas. The present investigation assessed the genetic variability of its ecotypes from Iran by employing morphological markers and essential oil components. The samples were collected from fifteen locations of Iran and were planted for evaluating morphological characters and also, the essential oil were identified by gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS) methods. Dendrogram of clustering with UPGMA algorithm and Euclidean distance separated 15 ecotypes to 5 main groups which in each group, ecotypes were same in geographical and habitat situation and biplot of PC1 and PC2 approved it. Principal components analysis (PCA) reduced the original 16 variables to 2 principal components that accounted for 95.83% of the total variance. The results of factor analysis showed that the first four factors mostly reflected most of the trait variations. Heritability of the morphological traits was high and the ecotypes exhibited the high genetic variations from the viewpoint of coefficient of variations. Based on our assessments, we showed high genetic variations for Iranian B. persicum germplasms.

Narrowband spectral indices for the estimation of chlorophyl along a precipitation gradient

Narrowband spectral indices have largely been used for the estimation of biochemical attributes of vegetation. However, most of the proposed indices were developed using a limited number of species and locations. In this study, a strong precipitation gradient in northern savannas of Australia was used to develop narrowband spectral indices for the estimation of leaf chlorophyll content and verify the spatial generality of the indices when applied to different species from different environmental conditions. Simple ratio indices (SRI) and normalized difference indices (NDI) were developed for samples taken from seven study sites along the transect. The results showed a limited transferability of the indices along the transect. Therefore, there is a need for more site-specific indices for large scale estimation of chlorophyll in the study area.

Evaluating the traits related with fruit flavor in cucumber.

Cucumber is an important fruity vegetable worldwide. It is consumed in some eastern countries like Iran not only for salad and pickled but also as a table fruit. Therefore, organoleptic characteristics including taste, aroma, firmness and other traits affecting on consumer savor should be more considered in cucumber breeding. In this study 16 selected Iranian local cultivars were planted and their fruits evaluated for aroma, taste and external attribute by panel test. In addition, proposed effective parameters including dry matter of fruits, potassium content, ash percent and texture firmness were measured. A significant difference was observed among the most traits. The results showed that the highest flavor related to genotypes with high taste, aroma, potassium content and dry matter and lowest skin firmness. G 85 and G 17 had the best taste and aroma. On the basis of cluster analysis, cultivars were divided into four groups. Aroma had a positive correlation with taste and dry matter. Increasing of dry matter content induced increasing of fruit aroma and taste.