Abstract
The recruitment of RNA polymerase II on a promoter is assisted by the assembly of basal transcriptional machinery in eukaryotes. The Spt-Ada-Gcn5-Acetyltransferase (SAGA) complex plays an important role in transcription regulation in eukaryotes. However, even in the advent of genome sequencing of various plants, SAGA complex has been poorly defined for their components and roles in plant development and physiological functions. Computational analysis of Arabidopsis thaliana and Oryza sativa genomes for SAGA complex resulted in the identification of 17 to 18 potential candidates for SAGA subunits. We have further classified the SAGA complex based on the conserved domains. Phylogenetic analysis revealed that the SAGA complex proteins are evolutionary conserved between plants, yeast and mammals. Functional annotation showed that they participate not only in chromatin remodeling and gene regulation, but also in different biological processes, which could be indirect and possibly mediated via the regulation of gene expression. The in silico expression analysis of the SAGA components in Arabidopsis and O. sativa clearly indicates that its components have a distinct expression profile at different developmental stages. The co-expression analysis of the SAGA components suggests that many of these subunits co-express at different developmental stages, during hormonal interaction and in response to stress conditions. Quantitative real-time PCR analysis of SAGA component genes further confirmed their expression in different plant tissues and stresses. The expression of representative salt, heat and light inducible genes were affected in mutant lines of SAGA subunits in Arabidopsis. Altogether, the present study reveals expedient evidences of involvement of the SAGA complex in plant gene regulation and stress responses.
Highlights
The regulation of gene expression is accomplished by the coordinated action of multiple events to ensure a perfect synchrony of cellular activities from chromatin modification to mRNA formation [1,2,3,4]
The SAGA complex has been previously shown to be associated with transcriptional regulation of ~10% RNA polymerase II-dependent S. cerevisiae genes, which contribute in response to DNA damage and other stress conditions such as heat, oxidation, and metabolic starvation [71, 72, 79]
We identified 18 putative SAGA complex subunits in Arabidopsis and O. sativa
Summary
The regulation of gene expression is accomplished by the coordinated action of multiple events to ensure a perfect synchrony of cellular activities from chromatin modification to mRNA formation [1,2,3,4]. The 1.8 megadalton S. cerevisiae SAGA complex is composed of 20 conserved proteins and contains different classes of transcriptional co-activator proteins such as SPT (Suppressor of Ty insertions), ADA (alteration/deficiency in activation), GCN5 (general control non-depressive), TAF (TBP-associated factors) proteins and DUBm (deubiquitylation module) [17]. These proteins are organized into different functional and structural sub-modules and thereby executing several cellular functions: nucleosomal histone acetyltransferase (HAT), histone deubiquitinylation, TATA-binding protein (TBP) binding and activator binding [10, 13, 18]
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