A Bacterial Transgene for Catalase Protects Translation of D1 Protein during Exposure of Salt-Stressed Tobacco Leaves to Strong Light

Khaled Al-Taweel,Yukinori Yabuta,Norio Murata,Shigeru Shigeoka,Akira Wadano,Toshio Iwaki

doi:10.1104/pp.107.101733

Khaled Al-Taweel, Yukinori Yabuta + Show 4 more

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https://doi.org/10.1104/pp.107.101733

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Abstract

During photoinhibition of photosystem II (PSII) in cyanobacteria, salt stress inhibits the repair of photodamaged PSII and, in particular, the synthesis of the D1 protein (D1). We investigated the effects of salt stress on the repair of PSII and the synthesis of D1 in wild-type tobacco (Nicotiana tabacum 'Xanthi') and in transformed plants that harbored the katE gene for catalase from Escherichia coli. Salt stress due to NaCl enhanced the photoinhibition of PSII in leaf discs from both wild-type and katE-transformed plants, but the effect of salt stress was less significant in the transformed plants than in wild-type plants. In the presence of lincomycin, which inhibits protein synthesis in chloroplasts, the activity of PSII decreased rapidly and at similar rates in both types of leaf disc during photoinhibition, and the observation suggests that repair of PSII was protected by the transgene-coded enzyme. Incorporation of [(35)S]methionine into D1 during photoinhibition was inhibited by salt stress, and the transformation mitigated this inhibitory effect. Northern blotting revealed that the level of psbA transcripts was not significantly affected by salt stress or by the transformation. Our results suggest that salt stress enhanced photoinhibition by inhibiting repair of PSII and that the katE transgene increased the resistance of the chloroplast's translational machinery to salt stress by scavenging hydrogen peroxide.

Highlights

During photoinhibition of photosystem II (PSII) in cyanobacteria, salt stress inhibits the repair of photodamaged PSII and, in particular, the synthesis of the D1 protein (D1)
We introduced the katE for catalase of Escherichia coli into tobacco (Nicotiana tabacum) and into tomato (Solanum lycopersicon), with cDNA for a transit peptide that allowed the resultant catalase to enter the stroma of chloroplasts (Shikanai et al, 1998; Mohamed et al, 2003)
To examine the contribution of de novo synthesis of chloroplast genome-encoded proteins to the salt stress-enhanced photoinhibition of PSII, we treated leaves with lincomycin as described in ‘‘Materials and Methods.’’ Figure 2, C and D, shows that inhibition of protein synthesis by lincomycin dramatically accelerated the inactivation of PSII in leaf discs from both wild-type and transgenic plants

Summary

Introduction

During photoinhibition of photosystem II (PSII) in cyanobacteria, salt stress inhibits the repair of photodamaged PSII and, in particular, the synthesis of the D1 protein (D1). D1 Biosynthesis in Plant under Environmental Stress to and repair of PSII in Synechocystis has demonstrated that salt stress (Allakhverdiev et al, 2002), oxidative stress (Nishiyama et al, 2001, 2004), and cold stress (Gombos et al, 1994) stimulate the apparent photoinhibition of PSII by inhibiting the repair of PSII and not by accelerating the actual photodamage to PSII. How the salt stress and the oxidative stress are related in the mechanism for the inhibition of the repair and, in particular, the translation of psbA transcripts remains to be resolved

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