Analysis of wheat root proteome under sodium chloride stress

Dissertation for Master's Degree in Agricultural Biotechnology

Keywords: two-dimensional electrophoresis, sodium chloride stress, wheat

Abstract:

Wheat (Triticum aestivum L.) is one of the oldest and first agricultural plants that is used as a raw material. Making bread has played an essential role in human nutrition. Considering the population growth and the increasing need for agricultural products, especially wheat, the production of wheat in the country should be increased. Due to the limited area of ??arable land, the increase in wheat production requires an increase in yield per unit area. Environmental stresses such as drought, salinity and cold play an important role on the performance of agricultural plants and their survival. Salinity stress is one of the most important abiotic stresses that has an adverse effect on the quantity and quality of crops, so that 20% of irrigated agricultural lands in the world are affected by salinity stress. Therefore, evaluating and investigating the molecular mechanism of resistance and sensitivity to sodium chloride stress in different wheat cultivars is of special importance in this regard. For this purpose, a repeated experiment was carried out in 2013 in the growth chamber under controlled conditions in the Faculty of Agriculture of Tabriz University. In this experiment, Arta (susceptible) and Bam (resistant) cultivars were used in two stress levels of 250 mm and no stress based on a completely random design in three replications. The time of applying stress was the two-leaf stage of the plants. After the emergence of stress symptoms, samples were taken and morphological traits such as root length, root volume, fresh weight, dry weight, root number and root proline content were investigated. Treatment of wheat cultivars with sodium chloride salt for one week did not cause statistically significant changes in root-related traits including length, weight and number of roots. It seems that the short period of proximity of plants with stress and the high rate of change are the main reasons for such a response. Dry weight and root number traits were significant at five and one percent probability levels, respectively. Sodium chloride stress increased the amount of proline in both sensitive and tolerant cultivars; Although the increase of proline in the sensitive variety was much higher than the tolerant variety. Investigation of wheat root proteome in sensitive variety by two-dimensional electrophoresis method led to the identification of 21 protein spots with significant expression changes, of which six protein spots showed increased expression and 15 protein spots showed decreased expression. In the strain, 49 protein spots were significantly altered in expression, among which 14 protein spots showed increased expression and 35 protein spots showed decreased expression. The proteins found were divided into important groups based on their biological function, such as proteins involved in energy metabolism, ROS inhibitors and detoxification, protein translation, processing and degradation, proteins associated with the cell wall, proteins associated with the metabolism of amino acids and hormones, the signal transmission network involved in the response to sodium chloride stress, the cell skeleton, proteins associated with transcription, proteins associated with the correlation of mRNA and protein levels.

Introduction

Wheat (Triticum aestivum L.) is one of the most important crops that has been used as the most important source of food since many years ago, before humans realized the uses of other plants. This plant is the most important agricultural product of Iran in terms of production and cultivated area (Khodabandeh, 2012). Considering the population growth and the increasing need for agricultural products, especially wheat, the production of wheat in the country should be increased. . Due to the limited area of ??arable land, the increase in wheat production requires an increase in yield per unit area. Increasing the yield per unit area can be achieved in two ways, one is the application of advanced agricultural methods and the other is the production of suitable cultivars in terms of quality and quantity of yield, resistance to diseases and tolerance of environmental stresses (Ehdaei, 2018). Many living organisms such as plant pathogenic viruses, bacteria, fungi, nematodes, insects and some flowering plants are plant parasites; which are referred to as "biological stresses". In contrast, "abiotic stresses" are imposed on plants by non-living things or materials or conditions.Salinity, ambient temperature, relative humidity, sunlight, soil nutrients and other physicochemical characteristics of soil cause abiotic stresses in plants (Nagarajan, 2010). Environmental stresses such as drought, salinity and cold have an important role on the performance of agricultural plants and their survival (Latini et al., 2007). Salinity stress is one of the most important abiotic stresses that has an adverse effect on the quantity and quality of crops, so that 20% of irrigated agricultural lands in the world are affected by salinity stress (Zhao et al., 2007). Due to Iran's location in the arid and semi-arid climate region, nearly 50% of the cultivated area of ??agricultural crops is faced with varying degrees of salinity and alkalinity problems (Mir Mohammadi Meybedi and Qara Yazi, 2013). 2011).  Proteomics is a method based on two-dimensional electrophoresis [1]. Each protein has an isoelectric point where the positive and negative charges of the protein are equal. In the first dimension electrophoresis, they use this property. The gel of the first dimension is transferred to the second dimension, which is the usual SDS-PAGE electrophoresis. In second dimension electrophoresis, the movement of proteins in the electric field is based on molecular weight (Leibler, 2002). Proteomics can be a powerful tool to identify candidate genes for stress resistance (Chen and Harmon, 2006). Several researches have used proteomics to identify salinity-responsive proteins. Many proteins have been found whose expression is regulated according to salt concentration. These proteins are involved in the process of energy metabolism, ROS inhibitors and detoxification of enzymes, protein translation, processing and degradation, proteins related to the cell wall, proteins related to the metabolism of amino acids and hormones, the signal transmission network involved in the response to sodium chloride stress, the cell skeleton, proteins related to transcription and proteins related to the correlation of mRNA and protein levels (Jiang et al., 2007).

Abstract:

Wheat (Triticum aestivum L.) is the oldest and the first crops played a key role as raw material for bread making in human nutrition. Due to population growth and increasing demand for agricultural products, wheat production should be increased in the country. Due to limited arable ground, increasing wheat production is required to increase the yield. Environmental stresses such as drought, salinity and low temperature have an impact on crop yield and their survival. Salinity is one of the abiotic stresses that adversely affect the quantity and quality of crops in such a way that 20 percent of the world's irrigated agricultural lands are affected by salinity. Therefore, assessment of molecular mechanism resistance and sensitivity to sodium chloride stress in different varieties of wheat is important. This experiment was carried out in 1391 in a growth chamber under controlled conditions at the Faculty of Agriculture, University of Tabriz. In this experiment, two varieties, Arta (susceptible) and Bam (resistance), were grown in both non-stress and stress conditions of 250 mM NaCl based on a completely randomized design with three replications. Stress was imposed when the seedlings had two leaves. By observing the symptoms of stress, the sampling was performed for morphological characteristics such as root length, root volume, shoot wet and dry weight, root numbers and proline content in the roots. Arta treatment of wheat varieties with sodium chloride for a week, did not affect significant changes in root related traits statistically. It seems that short period of exposure to stress and high coefficient of variation for most of the traits are the main reasons for such a response. But number and root dry weight, showed significant changes. NaCl stress increased proline content in both sensitive and tolerant cultivars but, the increase in susceptible variety was far more than tolerant varieties.