OfLCYB positively regulates drought and heat tolerance by modulating ROS scavenging in Osmanthus fragrans

Abstract

Osmanthus fragrans is an important tree in Asia, widely used in gardening and landscaping. As the global climate changes, the tree's growth and development are significantly affected by drought and heat stresses. Lycopene β-cyclase (LCYB) is a pivotal enzyme in the carotenoid pathway and plays an important role in abiotic stress responses. However, the function of the OfLCYB gene in the regulation of drought and heat tolerance is still unclear. In O. fragrans, OfLCYB expression was significantly induced by drought and heat treatments, and OfLCYB localized in the chloroplasts. Meanwhile, GUS staining of OfLCYB promoter showed that its promoter activity was dramatically activated by drought and heat treatments. Functional analysis showed that OfLCYB overexpression significantly improved the drought and heat tolerance of yeast cells, O. fragrans calli, and Arabidopsis. And the decrease of H2O2 concentration was found in the OfLCYB-overexpressing O. fragrans calli and Arabidopsis leaves. Furthermore, RNA-seq was performed and revealed that ROS scavenging-related genes were upregulated in the OfLCYB-overexpressing O. fragrans calli, especially the expression of APX, CAT, GPX, and PRX genes were significantly induced by drought and heat stresses. Therefore, we speculated that the OfLCYB gene contributes to the improvement of drought and heat tolerance by reducing the H2O2 accumulation through activating the expression of reactive oxygen species (ROS) scavenging-related genes in O. fragrans. Our results provide valuable insights into the role of the OfLCYB gene in the regulation of abiotic stress tolerance, with implications for future molecular breeding of ornamental plants.