Genome-wide analysis of protein disorder in A. thaliana. Implications for plasticity and adaptability

Intrinsically Disordered Proteins/Regions (IDPs/IDRs) are finally recognized as a widespread phenomenon having key cellular functions. Still, many functional roles need to be unveiled. Molecular interactions mediated by IDPs/IDRs have affinity/specificity properties ideal for certain types of protein interactions, such as those of signalling and cell cycle control. IDPs conformational flexibility allows them to recognize and interact with multiple partners, and confers them larger interaction surfaces that may increase interaction speed. We present the first large-scale study of IDPs in Arabidopsis thaliana, the most widely used model organism in plant molecular biology. While well characterized in human, intrinsic disorder (ID) in Arabidopsis is starting to be unveiled, and has been reported only in specific biological functions of given proteins. This work includes an ID comparison for Arabidopsis and human. We predicted disorder for all Arabidopsis and human proteins and retrieved their corresponding Gene Ontology (GO) annotations. Using GO classes annotating both organisms, we analysed disorder levels of their corresponding proteins. Results show that in general, human proteins are more disordered than Arabidopsis ones. However, certain GO classes, mainly related to environmental response, are significantly enriched in disorder for Arabidopsis proteins. We propose that because plants cannot escape from environmental stresses as humans can, they use ID as a simple, fast mechanism, independent of transcriptional control, for introducing versatility so their biological processes quickly adapt and respond to changing conditions and environments.