Abstract

Sacred lotus (Nelumbo nucifera Gaertn.) seed is long-living and have various stress-resistance characteristics. We investigated the protecting mechanisms of lotus seeds against extreme high temperature by comparison of expression patterns of antioxidant genes in embryonic axes between exposure and non-exposure to extreme high temperature. It was shown that viability of seeds did not severely decline after exposure to 90°C for 24 h. Germination and growth were inhibited and H₂O₂ was accumulated at high level in the lotus embryonic axes germinated after heat treatment. Transcriptional levels of superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase (POD), glutathione peroxidase (GPX) and thioredoxin-dependent peroxidase (TPX) encoding genes were induced to rise at late germination stage. Transcriptional levels of APX, POD, GPX and alternative oxidase (AOX) encoding genes were also immediately stimulated and up-regulated after heat treatment. These results suggest that the embryonic axes of sacred lotus maintain a protective and recovery mechanism from heat damage during and after exposure to extreme high temperature. Furthermore, the recovery of antioxidant gene expression enhanced tolerance to extreme high-temperature stress in sacred lotus.

Key words: Antioxidant gene, high temperature, seed germination, Nelumbo nuciferaGaertn.

Abbreviation

AOX, Alternative oxidase; APX, ascorbate peroxidase; DAB, 3,3′-diaminobenzidine; GPX, glutathione peroxidase; GSH, glutathione; PCR, polymerase chain reaction; POD, peroxidase; ROS, reactive oxygen species; SOD, superoxide dismutase; TPX, thioredoxin-dependent peroxidase; Trx, thioredoxin.