Overexpression of the OsIMP Gene Increases the Accumulation of Inositol and Confers Enhanced Cold Tolerance in Tobacco through Modulation of the Antioxidant Enzymes’ Activities

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.

Effect of Rhizobium Symbiosis on Low-Temperature Tolerance and Antioxidant Response in Alfalfa (Medicago sativa L.)

“…Further, since the AN group received less oxidative stress, this may be due to the fact that rhizobium symbiosis stimulates host plants to produce additional antioxidants. Our results are consistent with those of Zhang R.X. et al (2017) and Kakar et al (2016), who found that cold-resistant plants received less oxidative stress and were capable of higher antioxidant enzyme activity.…”

Organic Molecules from Biochar Leacheates Have a Positive Effect on Rice Seedling Cold Tolerance

“…Cold stress also leads to the overproduction of ROS which cause the lipidic peroxidation of plant cell membranes and the production of excess MDA and H 2 O 2 (Hodgson and Raison, 1991 ). Thus, MDA and H 2 O 2 are two important indicators of general lipid peroxidation, a process that results in the destruction of cell membrane structures (Hodges et al, 1999 ; An et al, 2016 ; Zhang et al, 2017 ). Increased MDA and H 2 O 2 concentrations damage metabolism by causing oxidative injury to rice cells (Zhang et al, 2017 ); thus, the fact that our results reveal lower MDA and H 2 O 2 contents following treatment with higher biochar leacheate concentrations at low temperatures (Figures 2A,B ) implies that rice plants can alleviate membrane damage when faced with these conditions.…”

“…Thus, MDA and H 2 O 2 are two important indicators of general lipid peroxidation, a process that results in the destruction of cell membrane structures (Hodges et al, 1999 ; An et al, 2016 ; Zhang et al, 2017 ). Increased MDA and H 2 O 2 concentrations damage metabolism by causing oxidative injury to rice cells (Zhang et al, 2017 ); thus, the fact that our results reveal lower MDA and H 2 O 2 contents following treatment with higher biochar leacheate concentrations at low temperatures (Figures 2A,B ) implies that rice plants can alleviate membrane damage when faced with these conditions. Plants have had to develop various methods to mitigate all kinds of biotic and abiotic stresses in order to survive, and SOD, POD, and CAT are all important enzymes from within the antioxidant defense system that mitigate oxidative damage by cleaning up excessive ROS in plants cells under low temperature (Li et al, 2015 ).…”

The occurrence and accumulation of d-pinitol in fenugreek (Trigonella foenum graecum L.)

“…In leaves of red clover, the concentration of d-pinitol ranged from 14 to 20 mg g −1 DW under optimal water conditions, and up to 110-120 mg g −1 DW under drought stress (Yates et al 2014). An increase in the d-pinitol concentration under drought stress was also found in soybean (Streeter et al 2001), Cicer arietinum (Matos et al 2010), alfalfa (Kang et al 2011) and Medicago truncatula (Zhang et al 2017). In our study, fenugreek plants grew under suitable watering conditions.…”

“…Cyclitols can function as "compatible solutes" (Valluru and Van den Ende 2011), osmolytes (Matos et al 2010) and antioxidants (scavenging of hydroxyl radicals, Nishizawa et al 2008). Moreover, cyclitols can regulate the antioxidant systems activity Zhang et al 2017) and facilitate ion transport under salinity stress (Sengupta et al 2008). However, under stress conditions affecting osmotic potential in cells, the short-term turnover of cyclitols is very low (Smith and Philips 1982;Merchant and Richter 2011).…”