Abstract
Inositol is a cyclic polyol that is involved in various physiological processes, including signal transduction and stress adaptation in plants. l-myo-inositol monophosphatase (IMPase) is one of the metal-dependent phosphatase family members and catalyzes the last reaction step of biosynthesis of inositol. Although increased IMPase activity induced by abiotic stress has been reported in chickpea plants, the role and regulation of the IMP gene in rice (Oryza sativa L.) remains poorly understood. In the present work, we obtained a full-length cDNA sequence coding IMPase in the cold tolerant rice landraces in Gaogonggui, which is named as OsIMP. Multiple alignment results have displayed that this sequence has characteristic signature motifs and conserved enzyme active sites of the phosphatase super family. Phylogenetic analysis showed that IMPase is most closely related to that of the wild rice Oryza brachyantha, while transcript analysis revealed that the expression of the OsIMP is significantly induced by cold stress and exogenous abscisic acid (ABA) treatment. Meanwhile, we cloned the 5’ flanking promoter sequence of the OsIMP gene and identified several important cis-acting elements, such as LTR (low-temperature responsiveness), TCA-element (salicylic acid responsiveness), ABRE-element (abscisic acid responsiveness), GARE-motif (gibberellin responsive), MBS (MYB Binding Site) and other cis-acting elements related to defense and stress responsiveness. To further investigate the potential function of the OsIMP gene, we generated transgenic tobacco plants overexpressing the OsIMP gene and the cold tolerance test indicated that these transgenic tobacco plants exhibit improved cold tolerance. Furthermore, transgenic tobacco plants have a lower level of hydrogen peroxide (H2O2) and malondialdehyde (MDA), and a higher content of total chlorophyll as well as increased antioxidant enzyme activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), when compared to wild type (WT) tobacco plants under normal and cold stress conditions.
Highlights
Rice is one of the most important cereal crops in developing countries, and is the main source of food for nearly half of the population in the world [1]
To compare the molecular evolutionary relationships of inositol monophosphatase (IMPase) with that of other species, we downloaded 15 sequences encoding IMPase from plants and bacteria by BLAST searches from the National Center for Biotechnology Information (NCBI) database, and the phylogenetic analysis indicated that the IMPase in Gaogonggui is most closely related to that of the wild rice Oryza brachyantha (Figure 2)
wild type (WT) plants significantly of plants, including decreased synthesis of total chlorophyll, well as an increase in thelines amount decreases after 24 h the of cold stress treatment, whereas significant as reduction from transgenic was of reactive oxygen species (ROS), which to of peroxidation the cellular membrane lipids and overproduction observed over aleads period
Summary
Rice is one of the most important cereal crops in developing countries, and is the main source of food for nearly half of the population in the world [1]. The development of cold-tolerant rice cultivation is an important goal of rice breeding programs. Over the past several decades, researchers have made great efforts to enhance the resistance to cold stress in rice by conventional breeding strategies, but they have seemed to not be effective because of the complex traits of the cold stress response in plants [2]. With the development of the modern techniques of molecular biology, many novel genes improving the cold tolerance have been cloned and characterized in rice. The rapid advancement in genetic engineering technology, together with precise and efficient DNA transformation methods, have made it possible to acquire genetically modified rice plants with improved cold tolerance [3,4,5,6]
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