Diversity of Plant Heat Shock Factors: Regulation, Interactions and Functions.

Plants Heat Shock Factors (HSFs) are encoded by large gene families with variable structure, expression and function. HSFs are components of complex signaling systems which control responses not only to high temperatures but also to a number of abiotic stresses such as cold, drought, hypoxic conditions, soil salinity, toxic minerals, strong irradiation and to pathogen threats. Here we provide an overview of the diverse world of plant HSFs through compilation and analysis of their functional versatility, diverse regulation and interactions. Bioinformatic data on gene expression profiles of Arabidopsis HSF genes were re-analysed to reveal their characteristic transcript patterns. While HSFs are regulated primarily at the transcript level, alternative splicing and posttranslational modifications such as phosphorylation and sumoylation provides further variability. Plant HSFs are involved in an intricate web of protein-protein interactions which adds considerable complexity to their biological function. A list of such interactions was compiled from public databases, published data and discussed to pinpoint their relevance in transcription control. Although most fundamental studies of plant HSFs have been conducted in the model plant, Arabidopsis, information on HSFs is accumulating in other plants such as tomato, rice, wheat and sunflower.. Understanding the function, interactions and regulation of HSFs will facilitate the design of novel strategies to use engineered proteins to improve tolerance and adaptation of crops to adverse environmental conditions.