Overexpression of GiLEA5-2.1, a late embryogenesis abundant gene LEA3 from Glycyrrhiza inflata Bat., enhances the drought and salt stress tolerance of transgenic tobacco (Nicotiana benthamiana)

Abstract

Abiotic stress, including drought and salt, reduces the yield of all major crop plants globally. Exploring the stress tolerance factors and mechanisms of dominant species is still an urgent task that is crucial for food and feed production. Glycyrrhiza inflata Bat., which is a halophytic plant, is economically important due to its medicinal, feeding, and ecological value. The plant is widely distributed in the salinized land of Northwest China. The plant demonstrates a robust capacity to withstand drought and salt stress, rendering it an excellent candidate for investigating the molecular mechanism behind drought and salt stress tolerance. Late embryogenesis abundant (LEA) proteins have been ascribed as significant stress tolerance factors attributed to their crucial role in improving the resilience against drought and salt stress. However, research on the salt tolerance mechanism of G. inflata is rare and limited to the physiological level. Furthermore, the role of the genes in G. inflata during abiotic stress conditions remains unclear. In this research, comprehensive knowledge of how G. inflata responds to salt stress was attained by investigating RNA-seq transcriptomes from the root of seedlings treated with 200 mM NaCl for three different time points (0 h, 3 h, and 48 h). Compared to the control, the roots exhibited a significant up-regulation in MDA and proline content as well as SOD and POD activity. The RNA-seq analysis revealed that there were 1938 DEGs that were common across various time points. GO and KEGG indicated that during salt stress, DEGs were found to be abundant in starch and sucrose metabolism, phenylpropanoid biosynthesis, glycolysis/gluconeogenesis, flavonoid biosynthesis, and the ABA signaling pathway. The correlation analysis suggested that Glyur000227s00015126.1 (GiLEA5–2.1) might be a candidate gene modulating the protection of G. inflata roots from salt stress. Apparently, the expression of GiLEA5–2.1 was triggered by drought and salt treatments. To investigate the role of GiLEA5–2.1 in drought and salt stress, plants overexpressed-GiLEA5–2.1 were generated. Overexpression of GiLEA5–2.1 in tobacco (N. benthamiana) could improve resistance against drought and salinity. Under drought and salty conditions, plants that overexpressed GiLEA5–2.1 exhibited enhanced activity of antioxidant enzymes and higher proline levels, along with decreased MDA content. Functional analyses demonstrate that GiLEA5–2.1 has a positive role in drought and salt treatments, it significantly increased the ability of tobacco to withstand drought and salt stress.