Enhancement of endogenous SA accumulation improves poor-nutrition stress tolerance in transgenic tobacco plants overexpressing a SA-binding protein gene

Abstract Salicylic acid (SA) plays an important role in the response of plants to abiotic stresses. Starvation stress affects plant cell metabolic activities, which further limits the normal growth and development of plants. It was reported that SA might play a regulatory role in the process of plant against starvation stress, but the mechanism involved in this process is still unclear. Thus, in this study, the transgenic plants overexpressing a SA binding protein 2 (SABP2) gene were exposed to starvation stress and the transgenic lines showed starvation-tolerant phenotype. Compared with wild-type (WT) plants, transgenic plants showed better growth status under poor-nutrition stress. Transgenic plants also showed more vigorous roots than WT plants. Physiological tests indicated that the transgenic plants showed higher relative water content (RWC), chlorophyll content, photosynthetic capacity, endogenous SA content, and lower ROS level compared to WT plants. Transcriptome analysis of tobacco plants identified 3, 748 differentially expressed genes (DEGs) between transgenic and WT plants under starvation stress. These DEGs are mainly involved in glycolysis/gluconeogenesis pathway group, MAPK signaling pathway group and plant hormone signal transduction pathway group. As determined by qPCR, up-regulated expression of fifteen genes such as abscisic acid receptor PYR1-like gene (NtPYR1-like), bidirectional sugar transporter N3-like gene (NtSWEETN3-like) and superoxide dismutase [Fe] chloroplastic-like gene (NtFeSOD-like), etc., was observed in transgenic plants under poor-nutrition stress which was in accordance with RNA-sequencing results. The modified pathways involved in plant hormone signaling are thought to be at least one of the main causes of the increased starvation tolerance of transgenic tobacco plants with altered SA homeostasis.