Document Type : Original Article

Authors

• Elham Younesi-Melerdi ¹
• Ghorbanali Nematzadeh ²
• Ali Pakdin-Parizi ³

¹ Ph.D. Student of Plant Biotechnology, Genetics and Agricultural Biotechnology Institute of Tabarestan, Sari Agricultural Sciences and Natural Resources University, Sari, Iran

² Professor, Department of Agronomy and Plant Breeding, PhD in Genetics, Sari Agricultural Sciences and Natural Resources University, Sari, Iran

³ Assistant Professor of Genetics and Agricultural Biotechnology, PhD in Biotechnology, Genetics and Agricultural Biotechnology Institute of Tabarestan, Sari Agricultural Sciences and Natural Resources University, Sari, Iran

Abstract

Introduction
Salt stress is one of the most important environmental stresses which severely affect agricultural economy in the world. Improving the salt-tolerance ability of crops and comprehending the complex mechanisms behind the salinity tolerance are two main fields of study in agricultural sciences.  Plants respond to the destructive effects of salinity through changes in physiological and molecular processes.
Materials and methods
In the present study the activity of SOD and APX antioxidant enzymes were measured. In addition to, changes in the expression of G-types-LecRLK, CIPK20, HSFA1a and C3H-ZF genes, involved in signaling and regulatory networks of Aeluropus littoralis, under salt stress has been investigated. The plant cuttings were cultured hydroponically under controlled conditions. The experimental design was consisted of a control (Hoagland’s solution with no NaCl added) and two treatments (200 and 400 mM NaCl). After 72 h of salt treatment, leaf samples were harvested and H₂O₂ content, SOD and APX enzymes activity were investigated. Then, total RNA was extracted using RNeasy Plant Mini Kit from leaf samples of control and treated plants. The integrity and quantity of RNA was determined by agarose gel electrophoresis and spectrophotometry, respectively. RNA was treated with RNase free DNase I and1 µg of total RNA used as template for first strand cDNA synthesis by Revert Aid Reverse Transcriptase kit according to manufacturer’s protocol. Three individual plants were taken for each treatment under each biological replicate and the final results represents the data obtained from three biological replicates. Data were statistically analyzed for the ANOVA and the significance of the differences between mean values of control and salinity-treated plants was determined using Tukey test.  For qRT-PCR analysis, three independent RNA samples were used for each sample, and each reaction was run in triplicate for both control and salt-treated samples.
Results and discussion
The results showed that the activity of antioxidant enzymes in both concentration 200 and 400 mM was significantly increased (p < 0.05). The lecRLK gene expression was not significantly changed among different treatments. The expression of CIPK20 gene were decreased 7 and 16 folds lower than control at 200 and 400 Mm of NaCl treatments, respectively. The obtained results revealed that expression of HSFA1a gene was positively associated with salt concentration (p < 0.05). So that, 11 and 13 fold HSFA1a gene expression more than control was observed. The expression of ZF30 gene was decreased significantly in both 200 and 400 mM NaCl treatments (p < 0.05). The results showed that the expression pattern of studied genes is different under salt stress conditions that can be related to the role of each gene, salt concentration and duration of stress.
Conclusion
Generally, a large number of genes in plants are induced after exposure to various abiotic stresses and function in different ways to confer stress tolerance to plants. Expression of genes involved in the transduction of salt stress signals is induced during early phases of stress response. Our study revealed not only the similar data to other published studies, but also some new information, such as the role of salt stress intensity and exposure time on signaling and regulatory mechanisms of response to salt stress. These results will benefit our understanding of the molecular mechanisms underlying resistance to salinity in A. littoralis.

Keywords

• Aeluropus littoralis
• Abiotic stress
• Gene expression
• Halophyte
• Salt-tolerance