Abstract：Abstract Aspartic proteinases (APs) are a family of protease enzymes, which plays pivotal roles in plant growth and development. This paper aims to investigate the preliminary biological function of APs in Rosa hybrida. A aspartic protease gene (AP) was cloned from Rosa hybrida 'Samantha' and named RhASP1 (GenBank No.: MG384616) by using reverse transcription-PCR (RT-PCR) method. The RhASP1 transcription expression characteristics were also examined using quantitative real-time PCR (qRT-PCR). The biological function by overexpressing RhASP1 in Arabidopsis thaliana was also investigated. The results showed that the open reading frame (ORF) of RhASP1 was 1 287 bp, which encoded 428 amino acids and belonged to B type APs. Qualitative PCR analysis showed that RhASP1 transcript expression levels was induced by NaCl treatment. Moreover, 24 h ethylene treatment and 3 h dehydration treatment significantly upregulated RhASP1 expression, respectively (P＜0.05). RhASP1 was overexpressed into Arabidopsis thaliana wild type (WT) by agrobacterium-mediated method. Three independent RhASP1-overexpressing lines with different expression levels were obtained to explore its biological function. The morphological and physiological performance of RhASP1 overexpressing lines were also investigated under salt stress. The seeding rates, increment primary root length and later root number of RhASP1-overexpressing plants were significantly higher than that of the WT plants under salt stress conditions(P＜0.05). The reactive oxygen species (ROS) levels of WT and RhASP1-overexpressing plants were also examined by histochemical staining. Both the RhASP1 transgenic and controls plants accumulated much brown sediment and blue sediment, whereas the RhASP1 transgenic plants were much lower than in the WT plants. The RhASP1-transgenic plants accumulated significantly less O2· and H2O2 compared with WT plants (P＜0.05). These findings examined preliminary biological function of RhASP1, and will provide new gene resources and basic theory foundation for stress breeding in Rosa hybrida.
