Application of the tolerance to extreme environment to land plants

Abstract

The ability of the primitive red alga Cyanidioschyzon merolae to survive in acidic environments at high temperatures was applied to produce acidand heat-tolerant transgenic plants. The C. merolae gene encoding a plasma membrane H+-ATPase was introduced into Arabidopsis thaliana, and the acid tolerance of the resulting transgenic plants was investigated. The transgenic seedlings were more acid-tolerant than the wild-type seedlings following a transient acid treatment. We also observed that the roots of transgenic plants grew longer than the wild-type roots. These results suggest that the C. merolae H+-ATPase may reinforce the acid tolerance of higher plants by enhancing proton pump activities. Furthermore, we produced transgenic A. thaliana plants overexpressing the C. merolae gene encoding the stromal ascorbate peroxidase (CmstAPX). Soluble APX activities were higher in CmstAPX-expressing plants than in the wild-type plants. Compared with the wild-type, the CmstAPX-expressing plants were more tolerant to high-temperature stress and oxidative stress induced by methyl viologen. Additionally, the CmstAPX-expressing plants retained the highest chlorophyllcontents after treatments with methyl viologen and high temperatures. Furthermore, the stroma and chloroplasts of the CmstAPX-expressing plants remained intact, whereas they disintegrated in the wild-type controls. These findings imply that the increased APX activity in the chloroplasts of CmstAPX-expressing plants enhances heat tolerance by increasing reactive oxygen species-scavenging capabilities at high temperatures.