Transcriptome analysis of antioxidant system response in Styrax tonkinensis seedlings under flood- drought abrupt alternation

Abstract

Abstract Background Styrax tonkinensis (Pierre) Craib ex Hartwich is a promising oil species with excellent fatty acid composition, making it a potential candidate for biofuel production. However, its expansion in the south provinces of Yangtze River region has been hindered by climate extremes such as flood-drought abrupt alternation (FDAA), which is caused by global warming. This species has low tolerance to waterlogging and drought, further restricting its growth in this region. To investigate the antioxidant system and the molecular response related to peroxisome pathway of S. tonkinensis under FDAA, we conducted FDAA and drought (DT) experiments on two-years old seedlings. We measured various growth indexes, reactive oxygen species content, the activity of two antioxidant enzymes and analyzed transcriptome of its seedlings under FDAA and DT conditions. Results The results displayed that the reduction in fresh weight was mainly observed in the leaves under FDAA condition. Through transcriptome analysis, we assembled a total of 1,111,088 unigenes (1,111,628,179 bp). We analyzed the differentially expressed genes (DEGs) related to reactive oxygen species (ROS) and antioxidant system. Generally, SOD1 and SOD2 genes in S. tonkinensis seedlings were upregulated to combat abiotic stresses. Our findings revealed that ROS accumulation was predominantly observed in leaves rather than roots under FDAA. Under FDAA circumstance, Protein Mpv17 (MPV17) showed the opposite reaction in leaves and roots with upregulation and downregulation, respectively. Conclusions The ROS generation triggered by MPV17 genes was not the main reason for the eventual mortality of the plant. Instead, plant mortality may be attributed to water loss during the waterlogging phase, decreased root water uptake capacity, and continued water loss during the subsequent drought period. This study establishes a scientific foundation for comprehending the morphological, physiological, and molecular facts of S. tonkinensis under FDAA conditions.