مجله زیست فناوری گیاهان زراعی
پیاپی 32 (زمستان 1399)

Downy mildew is one of the most important diseases of cucumber plants reducing production in the world. Despite the availability of some fungicides to control the disease, demands for new and reliable natural products has been increased. In this study, the effects of salicylic acid (SA) and Azelaic acid (AZA) on some biochemical properties and expression of defense genes in cucumber plants were studied. Gene expression analysis indicated that expression of both β-1,3- glucanase and chitinase genes were increased after inoculation with Pseudoperonospora cubensis, but this increase was much higher for chitinase gene in SA-treated plants and for β-1,3- glucanase in AZA-treated plants. Also, chlorophyll a, b and total flavonoids contents in AZA and SA-treated plants were higher compared to control 6 hours after inoculation with pathogen. Total phenolic content was also increased in SA and AZA treated plants compared to the control 6 and 72 hours after treatment, respectively. These findings indicate that pretreatment of cucumber plants with SA and AZA prompts faster defense responses and increases the efficiency of the defense system against downy mildew.

Calcineurin B-like proteins (CBLs), which act as a secondary messenger molecule in the subfamily of the calcium sensor gene family, play a key role in regulating physiological processes, plant growth and development. In order to identification and comparison of proteins involving in calcium signaling in two model of halophyte and glycophyte plants, in silico analysis of the CBL gene family were done in Aeluropus littoralis and Arabidopsis thaliana. Based on sequence homology and orthological relationships with Arabidopsis genes, 6 genes identified in Aeluropus were classified into three protein groups: AlCBL4, AlCBL2 and AlCBL10. Multiple sequence allignment of the CBL gene family in Aeluropus littoralis confirmed the presence of four EF-hand domains in all genes, which provide a structure for calcium ion binding. The high similarity of the physicochemical properties of most Aeluropus proteins to Arabidopsis as well as the strong orthological relationship with each other may indicate the preservation of the function of these genes in the evolutionary process. Analysis of AtCBLs expression patterns in different organs/ abiotic stresses showed that these genes have unique expression profiles due to functional and structural convergent. Different expression profiles of AlCBLs in Aeluropus transcriptome would be an evidence for the functional divergent of these genes. The results obtained from this study can provide valuable information about the properties of this gene family and their functional roles in tolerating to abiotic stresses for future studies.

Sour lime (Citrus aurantifolia L.) is one of the most important woody plants is widely known for its recalcitrance to genetic transformation. We aimed herein to evaluate effective factors influencing the transformation efficiency and the reduction of chimeric transgenic shoots in sour lime. Epicotyl and internode explants were genetically transformed with different Agrobacterium tumefaciens strains e.g., LBA4404, GV3850, and GV3101, harboring the vectors pBI121 and pCAMBIA3301 containing β-glucuronidase (GUS) as a reporter gene. The effect of the following factors was evaluated: Agrobacterium concentration (OD600=0.3, 0.5 and 1), during inoculation (5 seconds, 10 minutes and 30 minutes), co-culture (2 and 3 days), and the selection regime (phosphinothricin at 1, 3, 5 and 10 mg/l and kanamycin at 25, 50, 75 and 100 mg/l). In following, transformation efficiency and the chimeric transgenic shoots rate were respectively confirmed by PCR and GUS assays. The results showed that Agrobacterium strain LBA4404, at the OD600 of 0.5, with 5 seconds (for epicotyl) and 10 minutes (for internode) inoculation at two-day co-culture period, were identified the most suitable treatments for both explants. The transformation frequencies ranged from 0.93% for internode on DKW medium containing 1.0 mg/l of phosphinothricin to 14.29% for epicotyl on DKW medium containing 50 mg/l of kanamycin. Inclusion of the high-level of selective treatments, improved the transformation rate through decreasing frequency escape and chimeric transgenic shoots. These findings provide novel insights into the appropriate procedure to constitute non-chimeric lime transgenic shoots.

Phosphite is a reduced form of phosphate, wherein an oxygen replaces a hydrogen atom, and this substitution has a significant effect on its performance in living organisms. Phosphite is readily transfered into plant cells through phosphate transporters. However, plants do not have the ability to use phosphite as a phosphorus resourc such that this property has limited the use of phosphite as fertilizer; however, phosphite has been used as a fungicide and biostimulant in agriculture. Some bacteria are able to oxidize phosphite into phosphate to cover for various cellular functions. In the last decade, the molecular mechanism of this biological oxidation has been elucidated to occure by the enzyme phosphite oxidoreductase or phosphite dehydrogenase. Phosphite is produced in large quantities in various chemical industries as a by-product or waste that is not recycled. The identification of the enzyme phosphite dehydrogenase, that catalyses the oxidation of phosphite to phosphate, has opened a new path for the recycle of this waste. Recently, there have been reports for the production of transgenic plants expressing ptxD gene. In practice, ptxD gene can be used as a marker in the selection of transgenic plants. By producing these transgenic plants, phosphite can be used as a herbicide and even as a phosphorus fertilizer.

Saponaria officinalis is a perennial plant of the clove family. Hairy root culture system is a suitable alternative to improve the production of compounds with medicinal value. Extensive application of nanotechnology in hairy root culture is a suitable substrate for the production of active elements. In this study, the effect of different concentrations of titanium dioxide nanoparticles (0, 10, 20, 30 and 50 mg / l) and two exposure times (24 and 48 hours) on growth rate, antioxidant capacity, phenol and flavonoid content, antioxidant enzymes activity, polyphenol compounds content and the amount of SO6 protein in soapy hairy roots were investigated. The highest and lowest fresh weight of hairy roots (3.09 and 0.96 g, respectively) were found in culture medium treated with 10 and 20 mg / l titanium dioxide nanoparticles at 48 and 24 hours of exposure time, respectively. The highest total Phenol (9.79 mg GAE per g FW) and flavonoid (1.06 mg Que per g FW) content were observed in hairy roots treated with 50 and 30 mg / l titanium dioxide nanoparticles at 24 and 48 hours of exposure time respectively. The highest amount of most polyphenols including rosmarinic acid, cinnamic acid and rutin were achieved during 24 hours of treatment. The highest levels of SO6 protein was obtained in hairy roots treated with 50 mg/l titanium dioxide nanoparticles after 48 hours. By laboratory optimization of hairy root production of soap plant, SO6 can be produced in fermenter.

In this study, the type and frequency of regulatory elements in the promoter regions of DVL gene family in Aeluropus littoralis were studied. Relative expression of AlDVL8 gene as a member of this family was also measured under the salinity stress, salicylic acid, gibberellic acid and cytokinin. The results of the promoter study indicated that, this gene family has different regulatory elements for responding to stresses and hormones. Some of these regulatory elements are present in the promoter region of all genes, possibly indicating the general role of DVLs. Some others are present only in the promoter region of some genes that may be related to their specific activity. Treatments other than cytokinin increased gene expression in the shoot at 3, 12, and 24 hours and decreased expression at 6 hours. Cytokinin treatment at all times increased gene expression. In the root, almost the reverse trend of gene expression was observed, so that at 6 hours, increased gene expression was observed in all treatments, and at 12 and 24 hours, decreased expression was observed in all treatments. The results of this study showed that the expression of AlDVL8 gene in shoot and root organs was induced by experimental treatments and its expression was inverse in these two different tissues. Due to the changes in hormones during stress, expression induction of this gene family, and the presence of stress-responsive elements in the promoter regions of these genes, this gene family can be suggested as a candidate for stress tolerance.