Isolation, cloning and analysis of promoters of genes of the GH3 family in salt tolerant rice (Oryza sativa, L.)

This thesis aims to explore the varying responses to salt stress observed in two Italian rice varieties, Vialone Nano and Baldo, focusing on the characterization of the genes that are responsible for Baldo’s greater tolerance to this type of stress. Notably, a potential correlation between salt tolerance levels and the expression of certain genes belonging to the GH3 family has been observed. Specifically, among the different GH3 genes, the OsGH3.1, OsGH3.4, OsGH3.8 and OsGH3.9 have shown increased expression in the roots of Baldo compared to Vialone Nano under salt stress conditions. More interestingly, the OsGH3.9 genes appeared to be expressed only in the roots of the salt-tolerant variety, suggesting its potential role as a marker of salt tolerance in rice. Furthermore, the differential expression of this gene observed different rice varieties appeared not to be linked to alterations of the promoter sequence itself but rather to differences in methylation levels of its promoter region. Therefore, a key aspect of this project is to analyse and compare the methylation patterns in the OsGH3.9 gene's promoter region between the salt-sensitive (Vialone Nano) and salt-tolerant (Baldo) varieties. Additionally, To determine whether OsGH3.9 and OsGH3.4 GH3.4 shared a similar mechanism, the expression profile of the two genes was analysed in the roots of both rice varieties following cytokinin (CK) treatment.