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Abstract
Auxin/indoleacetic acid (Aux/IAA) proteins play an important regulatory role in the developmental process of plants and their responses to stresses. A previous study has shown that constitutive expression of OsIAA18, an Aux/IAA transcription factor gene of rice improved salt and osmotic tolerance in transgenic Arabidopsis plants. However, little work is known about the regulatory functions of the OsIAA18 gene in regulating the abiotic stress tolerance of rice. In this study, the OsIAA18 gene was introduced into the rice cultivar, Zhonghua 11 and the OsIAA18 overexpression in rice plants exhibited significantly enhanced salt and drought tolerance compared to the wild type (WT). Moreover, overexpression of OsIAA18 in rice increased endogenous levels of abscisic acid (ABA) and the overexpression of OsIAA18 in rice plants showed hypersensitivity to exogenous ABA treatment at both the germination and postgermination stages compared to WT. Overexpression of OsIAA18 upregulated the genes involved in ABA biosynthesis and signaling pathways, proline biosynthesis pathway, and reactive oxygen species (ROS)-scavenging system in the overexpression of OsIAA18 in rice plants under salt and drought stresses. Proline content, superoxide dismutase (SOD), and peroxidase (POD) activities were significantly increased, whereas malonaldehyde (MDA), hydrogen peroxide (H2O2), and superoxide anion radical (O2–) content were significantly decreased in the transgenic plants under salt and drought stresses. Taken together, we suggest that OsIAA18 plays a positive role in drought and salt tolerance by regulating stress-induced ABA signaling. The OsIAA18 gene has a potential application in genetically modified crops with enhanced tolerance to abiotic stresses.
Highlights
Environmental abiotic stresses, such as salt and drought, impact the growth, development, and productivity of agricultural crops and are becoming serious threats to provide and satisfy the needs of a rapidly growing population worldwide (Munns and Tester, 2008; Wang et al, 2016; Zhu et al, 2020)
To explore whether OsIAA18 plays an important role in improving the agronomic traits through gene manipulation approaches, we introduced this gene to rice
The shoot and root lengths and the fresh weight of overexpressing OsIAA18 plants grown in Murashige and Skoog (MS) medium with 2.5 μM of abscisic acid (ABA) were significantly reduced compared to those of the control (Figure 5B). These results demonstrate that the overexpression of OsIAA18 makes transgenic seedlings hypersensitive to ABA in comparison to wild type (WT) plants, indicating that OsIAA18 may be a positive regulator of ABA signaling in rice
Summary
Environmental abiotic stresses, such as salt and drought, impact the growth, development, and productivity of agricultural crops and are becoming serious threats to provide and satisfy the needs of a rapidly growing population worldwide (Munns and Tester, 2008; Wang et al, 2016; Zhu et al, 2020). It is important to understand abiotic stress responses of rice for enhancing salt and drought tolerance. Auxin plays a very important role in a wide variety of plant developmental and physiological processes (Friml, 2003; Song et al, 2009; Li G. et al, 2020; Li W. et al, 2020). Auxin/indoleacetic acid (Aux/IAA) and auxin response factor (ARF) family proteins, as two important protein families of plants, play important roles in the developmental process and responses to phytohormones and stress treatments by means of controlling auxin-responsive transcription (Hagen and Guilfoyle, 2002; Liscum and Reed, 2002; Berleth et al, 2004; Song et al, 2009; Song and Xu, 2013). Domains III and IV of the C-terminal dimerization mediate homodimerization and heterodimerization among Aux/IAA and ARF proteins (Ulmasov et al, 1997; Hardtke et al, 2004; Song and Xu, 2013)
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