Abstract:

The AP2/ERF transcription factors are plant-specific transcription factors. Among them， those in the DREB subfamily have been widely reported to improve plant resistance to abiotic stresses. To explore the roles of DREB family members in Lilium pumilum， we identified correlations between the transcript levels of DREB transcription factor genes and drought tolerance. We isolated the cDNA of the LpDREB9 gene from the roots of L. pumilum， and then conducted bioinformatics and subcellular localization analyses. This gene was then introduced into the model plant Nicotiana tabacum to elucidate its role in drought tolerance. The open reading frame （ORF） of LpDREB9 gene was 462 bp， encoding a protein of 153 amino acids with a relative molecular weight of 17.054 kDa， the fat index of 73.46， and a pI value of 4.89. It was an unstable and hydrophilic protein. Subsequent analysis revealed the nuclear localization of the LpDREB9 protein. In an alignment analysis， the LpDREB9 gene showed the closest evolutionary relationship with its homologs in Lilium regale. Seeds and seedlings of wild-type （WT） tobacco and transgenic tobacco expressing LpDREB9 were exposed to abscisic acid and drought stress. Phenotypic and physiological parameters of the seedlings after natural drought stress and subsequent rehydration were determined. The results indicated that the LpDREB9 gene enhanced drought tolerance in transgenic tobacco plants， particularly under prolonged drought stress. The activities of superoxide dismutase， peroxidase， and catalase， as well as chlorophyll and proline levels， were significantly higher in the LpDREB9 transgenic tobacco than in WT （P<0.05）. The malondialdehyde content was markedly lower in transgenic tobacco plants than in WT （P<0.05）， indicative of a lower level of membrane lipid peroxidation. These findings underscore the heightened capacity to scavenge reactive oxygen species in transgenic tobacco expressing LpDREB9， leading to enhanced drought tolerance. Hence， the LpDREB9 gene plays a pivotal role in augmenting the drought tolerance of transgenic tobacco. These findings provide the basis for further research on stress resistance at the molecular level in L. pumilum.

Key words: Lilium pumilum, transcription factor, LpDREB9, bioinformatics analysis, phenotypes, drought resistance