Overexpression of the Maize psbA Gene Enhances Drought Tolerance Through Regulating Antioxidant System, Photosynthetic Capability, and Stress Defense Gene Expression in Tobacco.

Yongjin Huo,Meiping Wang,Zongliang Xia,Yangyang Wei

doi:10.3389/fpls.2015.01223

Abstract

The psbA (encoding D1 protein) plays an important role in protecting photosystem II (PSII) from oxidative damage in higher plants. In our previous study, the role of the psbA from maize (Zea mays. L) in response to SO2 stress was characterized. To date, information about the involvement of the psbA gene in drought response is scarce. Here we found that overexpression (OE) of ZmpsbA showed increased D1 protein abundance and enhanced drought stress tolerance in tobacco. The drought-tolerant phenotypes of the OE lines were accompanied by increases of key antioxidant enzymes SOD, CAT, and POD activities, but decreases of hydrogen peroxide, malondialdehyde, and ion leakage. Further investigation showed that the OE plants had much less reductions than the wild-type in the net photosynthesis rate (Pn), stomatal conductance (Gs), and the maximal photochemical efficiency of PSII (Fv/Fm) during drought stress; indicating that OE of ZmpsbA may alleviate photosynthesis inhibition during drought. qRT-PCR analysis revealed that there was significantly increased expression of NtLEA5, NtERD10C, NtAREB, and NtCDPK2 in ZmpsbA-OE lines. Together, our results indicate that ZmpsbA improves drought tolerance in tobacco possibly by alleviating photosynthesis reduction, reducing reactive oxygen species accumulation and membrane damage, and modulating stress defense gene expression. ZmpsbA could be exploited for engineering drought-tolerant plants in molecular breeding of crops.

Highlights

Photosystem II consists of a multi-protein complex and plays important roles in the oxygenevolving photosynthetic organisms (Wollman et al, 1999)
A 275-bp PCR product was amplified from both transgenic lines (OE-8 and OE-11), while no product was amplified from the wild type (WT) plants (Figure 1A)
Our genetic evidence suggests that ZmpsbA confers drought tolerance by possibly regulating antioxidant system, photosynthetic capability, and stress defense gene expression in tobacco

Summary

Introduction

Photosystem II consists of a multi-protein complex and plays important roles in the oxygenevolving photosynthetic organisms (Wollman et al, 1999). Through the PSII repair machinery, damaged D1 protein will be degraded and replaced by a new one so as to maintain stable photosynthesis (Baena-González and Aro, 2002; Adir et al, 2003). Zhang et al (2011) reported that a chloroplast-localized protein HCF243 functioned in maintaining D1 stability in Arabidopsis (Zhang et al, 2011). A more recent report showed that the D1 protein had a C-terminal processing, which is necessary for PSII function in Arabidopsis (Che et al, 2013). It has been reported that the D1 protein of PSII was protected from oxidative damage and degradation in the drought-tolerant transgenic plants (Almoguera et al, 2012)

Methods

Results

Conclusion