Involvement of OsGF14b Adaptation in the Drought Resistance of Rice Plants
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Drought stress is one of the major abiotic stresses that restrict plant growth and development. 14–3-3 proteins have been validated to regulate many biological processes in plants. Previous research demonstrated that OsGF14b plays different roles in panicle and leaf blast resistance. In this study, we researched the function of OsGF14b in drought resistance in rice.
Here, we report that OsGF14b was strongly induced by soil drought stress. In comparison with wild type (WT), the osgf14b mutant exhibited improved resistance to drought and osmotic stress by changing the content of stress-relevant parameters, complementation of the osgf14b mutant restored the drought sensitivity to WT levels, whereas the OsGF14b-overexpression lines exhibited enhanced sensitivity to drought and osmotic stress. The osgf14b mutant plants were hypersensitive to abscisic acid (ABA), while the OsGF14b-overexpression plants showed reduced sensitivity to ABA. Furthermore, mutation and overexpression of OsGF14b affected the expression of stress-related genes under normal growth conditions and/or drought stress conditions.
We have demonstrated that OsGF14b is involved in the drought resistance of rice plants, partially in an ABA-dependent manner.
KeywordsABA Rice 14–3-3 Drought resistance OsGF14b
Least significant difference
Murashige and skoog
Quantitative real time polymerase chain reaction
- RISD DB
Rice T-DNA Insertion Sequence Database
Reactive oxygen species
Drought is one of the main abiotic stresses affecting plant growth and yield. Sessile plants have evolved various effective mechanisms to cope with drought stress (Hu and Xiong 2014). Obtaining a better understanding of the molecular and genetic mechanism by which plants respond to drought stress has been the subject of intensive research over the past decade, and is expected to provide and essential foundation for future breeding and genetic engineering strategies (Xiang et al. 2008; Marshall et al. 2012; Tang et al. 2016; Srivastava et al. 2017; Liang et al. 2018; Lee et al. 2018; Yao et al., 2018).
14–3-3 proteins mainly function through binding and modulating the function of phosphorylated client proteins (de Boer et al. 2013). These are localized to various subcellular compartments and regulate a wide range of cellular processes (Paul et al. 2012). In higher plants, 14–3-3 proteins comprise a protein family and play important roles in regulating plant development and stress responses (Comparot et al. 2003; Denison et al. 2011). Some studies have implicated the function of 14–3-3 s in drought resistance from Arabidopsis, maize and Glycine soja (He et al. 2015; Campo et al. 2012; Sun et al. 2014). In rice, at least eight 14–3-3 isoforms (OsGF14 a-h) have been identified, and these isoforms display different expression patterns under various biotic and abiotic stresses (Chen et al. 2006; Xu and Shi 2006; Yashvardhini et al. 2018). The different roles of OsGF14e and OsGF14b in disease resistance have been reported (Manosalva et al. 2011; Liu et al. 2016b; Liu et al. 2016a). However, only OsGF14c’s roles in drought resistance were confirmed (Ho et al. 2013), and the functions of the other rice 14–3-3 proteins in this process are still unknown.
Stomatal status is generally important for drought response in plants, so we measured the stomatal conductance of the WT and transgenic plants (mutant and OE) under normal and drought conditions at 5.5- to 6.5-leaf stage. Under normal conditions, the stomatal conductance of osgf14b was significantly higher than that of DJ, whereas the stomatal conductance of OsGF14b-OE lines was significantly lower than that of Nip; Under drought conditions (without water for 3 d), the stomatal conductance of all plants was decreased compared with under normal conditions, but there was no significant difference between the WT and transgenic plants (Additional file 1: Figure S3). The results showed that although OsGF14b could negatively regulate the stomatal conductance under normal conditions, but had almost no impact on that under drought conditions, and stomatal conductance may be not associated with the drought resistance negatively regulated by OsGF14b.
Stresses usually cause damage in plants via oxidative stress involving the generation of reactive oxygen species (ROS), such as hydrogen peroxide (H2O2) (Zhu 2001). Malondialdehyde (MDA) is an indicator of oxidative attack on membrane lipids and ion leakage reflects membrane injury (Ouyang et al. 2010). Thus, we tested the H2O2 and MDA content of the leaves from transgenic (mutant or OE) and WT plants (DJ or Nip). After drought stress, the H2O2 and MDA content in the osgf14b mutant were all less than DJ, whereas the OsGF14b-OE lines accumulated more H2O2 and MDA than Nip. Under normal conditions, we found that these two OsGF14b-OE lines had fewer H2O2 than Nip, and OE-4 had higher MDA than Nip, but there were no significant differences on these between osgf14b and DJ (Fig.1d, e). Proline and soluble sugar are two important solutes in plant cells for improving drought resistance by increasing osmotic pressure (Zhou et al. 2009). Furthermore, we also examined the content of proline and soluble sugar. After drought stress, compared with WT, the proline levels of the osgf14b mutant increased, but those of OsGF14b-OE lines declined. All tested plants had similar proline content under normal growth conditions (Fig. 1f). When the soluble sugar content was compared, the osgf14b mutant showed higher soluble sugar levels than DJ, while the OsGF14b-OE lines showed lower sugar levels than Nip under both normal and drought conditions (Fig. 1g). Taken together, these results suggested that OsGF14b may negatively regulate the resistance to drought stress via changing the content of stress-relevant parameters.
Abscisic acid (ABA) signaling plays major roles in the drought stress (Zhang et al. 2006; Tang et al. 2016), and two previous studies showed that OsGF14b could be strongly induced by ABA (Chen et al. 2006; Yao et al. 2007). So we tested if OsGF14b is involved in ABA sensitivity of rice, which is an important aspect of ABA-dependent regulation. The osgf14b mutant and two OE lines (OE-2 and OE-4) were treated with 5 μM ABA, together with WT control. As shown in Fig. 2d, the osgf14b mutant seedlings were more sensitive to ABA compared to DJ. Moreover, the shoot length of the osgf14b mutant was significantly shorter than that of DJ under ABA treatment, but there was no significant difference under normal conditions. On the contrary, we found that the ABA sensitivity of OsGF14b-OE seedlings was decreased compared to Nip. In addition, the shoot length of OsGF14b-OE lines was much longer than that of Nip under ABA treatment. Nevertheless, no significant difference in these phenotypes was observed under normal conditions (Fig. 2e, f). Taken together, these results indicated that OsGF14b functions as a negative regulator of ABA signaling.
In conclusion, in this study we have demonstrated that OsGF14b is involved in the rice drought and osmotic resistance via changing the contents of stress-relevant parameters and the expression of stress-related genes, partially in an ABA-dependent manner. This findings presented here will provide a novel insight into the function of OsGF14b in rice.
The authors would like to thank Prof. Bin Liu (Rice Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, China) for providing the seeds of OsGF14b-overexpression lines.
LJP and XWF contributed to the experimental design. LJP, SXJ and LWC contributed to experiment performance and data analysis. LJP and XWF drafted the manuscript. ZJH and LJS contributed to good advice on designing the experiment and revising the manuscript. All authors read and approved the final manuscript.
This study was supported by the National Natural Science Foundation of China (31601232), Fujian Agriculture and Forestry University Program for Distinguished Young Scholar (xjq201706), the Natural Science Foundation of Fujian Province (2017 J05046), and China Postdoctoral Science Foundation (2017 M612108).
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The authors declare that they have no competing interests.
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