Arabidopsis TEMPRANILLO1 transcription factor AtTEM1 negatively regulates drought tolerance

Arabidopsis TEMPRANILLO 1 (AtTEM1) is a member of the RAV transcription factor subfamily and has plant-specific AP2 and B3 domains. This study demonstrated that AtTEM1 is localized in nuclei. Expression of AtTEM1 was discovered to be high in the flower, stem, rosette, and cauline leaf, but low in the silique and root tissue, and was strongly induced by drought and mannitol treatments. Compared with wild-type plants, the 35S::AtTEM1 plants bolted later and produced more rosette leaves before flowering, whereas, the AtTEM1 mutant plants (tem1) bolted earlier but produced an almost equal number of rosette leaves before flowering. Drought tolerance was significantly reduced in the 35S::AtTEM1 transgenic Arabidopsis plants, but was enhanced in the tem1 plants. Under drought and mannitol stresses, the 35S::AtTEM1 transgenic Arabidopsis exhibited increased relative electrical conductivity (REC), increased malondialdehyde (MDA) content, and decreased proline content compared with the wild type, whereas lower REC and MDA content and higher proline content were found in the tem1 plants. These results suggest that AtTEM1 in Arabidopsis functions as a negative regulator in response to drought and mannitol stresses. Therefore, AtTEM1 transcription factor is proposed to be a versatile regulator reacting negatively to both flowering time and drought stress.