Antioxidant System Response and cDNA-SCoT Marker Profiling in Phoenix dactylifera L. Plant under Salinity Stress

Hindawi International Journal of Genomics Volume 2017, Article ID 1537538, 10 pages https://doi.org/10.1155/2017/1537538 Research Article Antioxidant System Response and cDNA-SCoT Marker Profiling in Phoenix dactylifera L. Plant under Salinity Stress Fahad Al-Qurainy, Salim Khan, Mohammad Nadeem, Mohamed Tarroum, and Abdel-Rhman Z. Gaafar Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia Correspondence should be addressed to Salim Khan; Received 29 November 2016; Revised 23 April 2017; Accepted 2 May 2017; Published 18 June 2017 Academic Editor: Ferenc Olasz Copyright © 2017 Fahad Al-Qurainy et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Many Phoenix dactylifera (date palm) cultivars are grown in the arid and semiarid regions of the world, including Saudi Arabia. P. dactylifera is highly tolerant to salinity stress. To investigate the response of Khalas cultivar of P. dactylifera, two-month-old plants were treated with sodium chloride (50, 100, and 150 mM NaCl) for three months. Our result showed that proline content was higher in all treated plants compared to control plants. Thiobarbituric acid reactive substances (TBARS) were increased at 100 and 150 mM NaCl treatments; however, the result was found nonsignificant between control and plants treated at 50 mM NaCl. Similarly, enzyme activities of catalase (CAT) and superoxide dismutase (SOD) were 0.805 and 0.722 U/mg protein/min, respectively, and were greater at 100 and 150 mM NaCl treatments compared to the control plants. Total chlorophyll content and fresh weight of shoots and roots decreased substantially with the increase of salinity. A cDNA start codon-targeted (cDNASCoT) marker showed a variation in different gene expressions profiling between treated and untreated plants under various NaCl concentrations. 1. Introduction In recent decades, soil salinity has become a global agricultural constraint [1, 2]. Salinity is increasing on Arabic land, and more than 50% would be salinized by the year 2050, if suitable corrections are not made [3]. Furthermore, the salinized areas are increasing every year at a rate of 10% for different reasons including poor cultural practices, irrigation with saline water, weathering of native rocks, high surface evaporation, and low precipitation [4, 5]. Salt stress causes average yield losses of more than 50% in major crops in agriculture-based countries [6]. Reactive oxygen species (ROS) are produced in plant cells under salinity stress [7], which can damage the cells. It also affects many metabolic and physical processes of the plant, and as a result, the growth is hampered [8]. A high salinity stress causes osmotic and ionic stresses in the plant cells, which lead to several physiological and morphological modifications [9]. Phoenix dactylifera (date palm) is the main horticultural fruit tree in many arid and semiarid countries in the Middle East, North Africa, and Central America [10]. P. dactylifera can survive under extreme abiotic stresses, including conditions of drought, high temperature, and relatively high soil salinity levels [11–14]. The salinity stress affected the large area of arid and semiarid regions of agricultural field [15] and has impacted more losses in P. dactylifera and other crop species [16]. The antioxidant enzyme activities such as catalase (CAT) and superoxide dismutase (SOD) increase under salinity stress for scavenging regenerated ROS to protect the cell from damage [17, 18]. The enzyme SOD is found in various compartments of the cell and catalyzes the superoxide radicals (O2−) to H2O2 and O2 [19]. The H2O2 is removed from the cell by peroxidases and catalase [19–22]. The proline, an osmoprotectant, is produced under abiotic and biotic stresses [23] in plants. Heat and cold treatments can result in a significant increase in proline level in 2 the leaves and roots of P. dactylifera [14]. The changes occurred in SOD and chlorophyll a/b-binding protein under salt stress in P. dactylifera [24]. Thiobarbituric acid reactive substances (TBARS), which are produced in the plant cells, act as a potential indicator of damage under induction of stresses [25]. An increase in TBARS content under salinity stress can cause damage to membranes and also to particular cell tissues [26–28]. Usually, osmotic or salt stress induces TBARS accumulation [29]. TBARS accumulation in cowpea leaves under salinity stress depends on exposure time [30]. However, a reduction in TBARS level under salinity stress is poorly reported in the literature [31]. Different methods have been developed for the gene expression study in plants or animals such as cDNA microarray, cDNA-SRAP, cDNA-AFLP, serial analysis of gene expression (SAGE), suppression subtractive hybridization (SSH), representational difference analysis (RDA), and mRNA differential display (DD) [32–42]. All these markers have advantages and disadvantages based on the reproducibility of the results, available resources, technical expertise, and cost of development. A cDNA start codon-targeted (cDNA-SCoT) marker has been used for the study of gene expression in Saccharum officinarum, Mangifera indica, Phoenix dactylifera, and Dendrobium officinale [43–46]. However, this marker has also been used for the assessment of genetic diversity in various plant species [47–50]. A high degree of variability has been found among the germplasms of P. dactylifera under salinity and drought stresses [51]. Knowledge of molecular mechanisms under salinity and drought conditions in P. dactylifera is limited [52–57]. In the present study, we performed experiments on the Khalas cultivar of P. dactylifera to determine the antioxidant system response and gene expression profiling under salinity stress. 2. Materials and Methods A pot experiment was conducted in a growth chamber for salinity stress treatments in four replicates. The pots were filled with a mixture of sand and peat moss (3 : 1). The healthy seeds of P. dactylifera were surface sterilized with sodium hypochlorite solution (4.0% available chlorine) for 10 min and washed thoroughly four times with distilled water. The seeds were sown in plastic pots and watered at regular interval to maintain moisture for better germination. Salinity stress treatments were given to the two-month-old plants of Khalas cultivar of P. dactylifera for three months. Three concentrations of NaCl as low (T-50, 50 mM), intermediate (T-100, 100 mM), and high (T-150, 150 mM) were used to treat the plants. Each concentration of salt solution (100 ml) was given to each pot after two-week time intervals. 100 ml of 1/4 strength MS solution was added to each pot after two-week time intervals. The pots were maintained in the growth chamber at 26-27°C, photoperiod 16 h per day, and relative humidity of 7 (...truncated)