پژوهشنامه اصلاح گیاهان زراعی (Sep 2024)
The Effect of Iron Deficiency Stress on the Relative Expression of ZIP3, ZIP6, and ZIP7 Genes in Bread Wheat (Triticum aestivum L.) Cultivars
Abstract
Extended abstract Background: Bread Wheat is the most extensively cultivated wheat and one of the four major crops in the world that constitutes the principal food of more than 30% of the world population. Biotic and abiotic environmental stressors are major factors limiting plant growth and productivity, which play a significant role in determining the yield and production potential of plants by affecting morphological, physiological, biochemical, and molecular processes. Among the abiotic stresses, the deficiency of micronutrients in the soil is important. Micronutrients regulate food metabolism in humans, and their deficiency endangers human health. Iron and zinc are essential micronutrients for human health and cofactors of many vital enzymes involved in many human metabolic processes. In plants, iron is the most required element among all micronutrients. It is a part of the catalytic group of many oxidation and reduction enzymes and is required for chlorophyll synthesis. To facilitate the adequate uptake and prevent excessive absorption of iron, plants have developed a balanced network to regulate the uptake, use, and storage of ions. In fact, such adjustment processes depend on genes that regulate ion homeostasis in plants. Due to the existence of a large allohexaploid genome and technical challenges in wheat transformation, few genes involved in iron and zinc uptake, transfer, and storage have been characterized functionally. Considering the important role of ZIP proteins in iron uptake efficiency, investigating the expression of the ZIP genes in Fe-efficient and -inefficient bread wheat cultivars can be effective in improving Fe-efficient cultivars in this valuable crop. Therefore, this research aimed to evaluate the expression of ZIP3, ZIP6, and ZIP7 genes in the leaves and roots of two Fe-efficient and -inefficient bread wheat cultivars at different growth stages under iron deficiency stress. Methods: This research was carried out in a completely randomized design (CRD) based on a factorial experiment with three replications in the research greenhouse of the Faculty of Agriculture, Urmia University. The first factor was two Fe-efficient (Pishtaz) and -inefficient (Flat) bread wheat cultivars, the second factor was two soil iron levels (iron deficiency and sufficiency, respectively, 1.4 and 10 mg/kg of soil), and the third factor was two sampling stages (vegetative and reproductive, respectively, one month after planting and 30% heading). To evaluate the expression of genes, the roots and leaves of the plants were sampled at each growth stage. The seeds were obtained from the Iranian Seed and Plant Improvement Institute, disinfected with 1% hydrogen peroxide, and planted at a depth of 4 cm in the soil. The plants were irrigated using distilled water to the extent of field capacity during the growing period. Results: The results of variance analysis of the relative expression of all three studied genes showed that the interaction effect of cultivar × organ × sampling stage was significant at the probability level of 1%. The comparison of the means for the cultivar × organ × sampling stage interaction effect revealed the highest ZIP3 expression in the roots of the Fe-efficient cultivar (Pishtaz) in the vegetative and reproductive stages. The relative expression of this gene was higher in the roots of the Fe-inefficient cultivar (Falat) than that of the Fe-efficient cultivar (Pishtaz). However, the Fe-inefficient cultivar (Falat) showed the highest relative expression increase in the leaf in both reproductive and vegetative stages, but the difference in the gene expression level in the leaf between the two growth stages was not statistically significant. The lowest gene expression level in the leaf belonged to the Pishtaz cultivar. The comparison of the means of cultivar × organ × sampling stage for the ZIP6 gene indicated an increase in the relative expression of this gene in the roots of the Fe-efficient (Pishtaz) and -inefficient (Falat) varieties in the vegetative and reproductive stages, respectively. The comparison of the means of cultivar × organ × sampling stage for the ZIP7 gene indicated the highest relative expression of this gene in the roots of the Fe-efficient cultivar (Pishtaz) at the vegetative stage. The relative expression level of this gene in the root of the Fe-efficient variety in the vegetative stage was significantly higher than that in the reproductive stage. In both vegetative and reproductive stages in the leaf, the increase in gene expression was higher in the Fe-inefficient cultivar. Conclusion: The increased ZIP3 expression in iron deficiency conditions in the roots of the Fe-efficient cultivar at the vegetative stage demonstrates the possible role of this gene in Fe uptake from the soil and its transfer to the aerial parts of the plant in the early growth phase. The ZIP6 gene `was expressed in both roots and leaves throughout the entire growth period of the plant. However, the expression level of this gene increased with the age of the plant. Therefore, the ZIP6 gene is probably responsible for Fe uptake and transport to different organs throughout the entire growth period of the plant and plays an important role in preserving iron in iron deficiency conditions. The ZIP7 gene is expressed in both leaves and roots in iron deficiency conditions, but the level of expression is higher in the roots of the Fe-efficient variety during the vegetative stage. This gene may be involved in iron uptake from the soil and its transfer to aerial organs.
