Abstract
In higher plants, S(1)-basic region-leucine zipper (S(1)-bZIP) transcription factors fulfill crucial roles in the physiological homeostasis of carbon and amino acid metabolisms and stress responses. However, very little is known about the physiological role of S(1)-bZIP in cruciferous vegetables. Here, we analyzed the physiological function of S(1)-bZIP from Brassica rapa (BrbZIP-S) in modulating proline and sugar metabolism. Overexpression of BrbZIP-S in Nicotiana benthamiana resulted in delayed chlorophyll degradation during the response to dark conditions. Under heat stress or recovery conditions, the transgenic lines exhibited a lower accumulation of H(2)O(2), malondialdehyde, and protein carbonyls compared to the levels in transgenic control plants. These results strongly indicate that BrbZIP-S regulates plant tolerance against dark and heat stress. We propose that BrbZIP-S is a modulator of proline and sugar metabolism, which are required for energy homeostasis in response to environmental stress conditions.