Identification of cell wall genes modified by a permissive high temperature in Chinese cabbage

If plants are pre-exposed to moderate heat stress, they can acquire enhanced tolerance to otherwise lethal high temperatures. To elucidate gene regulatory events involved in the acquisition of thermotolerance, we here conducted a comprehensive transcriptomic analysis. Chinese cabbage microarrays (Brassica rapa EST 6.4 K) were used to compare gene expression of 7-day old seedlings exposed to permissive high temperatures over a time course (0, 0.25, 1, 3, and 12 h at 37 °C). Expression profiling showed that heat treatment triggered significant accumulation of heat shock proteins over time and that some cell wall-modificatory (CWM) genes were up-regulated at the later time points. This up-regulation of CWM genes was verified by reverse-transcription (RT)-PCR and histochemical analysis also provided evidence that cell wall thickness is increased by permissive heat treatment. These observations imply that the activation of CWM-related genes by permissive high temperature stress is an important response for the acquisition of thermotolerance.