Abstract
BackgroundLEA (late embryogenesis abundant) proteins have first been described about 25 years ago as accumulating late in plant seed development. They were later found in vegetative plant tissues following environmental stress and also in desiccation tolerant bacteria and invertebrates. Although they are widely assumed to play crucial roles in cellular dehydration tolerance, their physiological and biochemical functions are largely unknown.ResultsWe present a genome-wide analysis of LEA proteins and their encoding genes in Arabidopsis thaliana. We identified 51 LEA protein encoding genes in the Arabidopsis genome that could be classified into nine distinct groups. Expression studies were performed on all genes at different developmental stages, in different plant organs and under different stress and hormone treatments using quantitative RT-PCR. We found evidence of expression for all 51 genes. There was only little overlap between genes expressed in vegetative tissues and in seeds and expression levels were generally higher in seeds. Most genes encoding LEA proteins had abscisic acid response (ABRE) and/or low temperature response (LTRE) elements in their promoters and many genes containing the respective promoter elements were induced by abscisic acid, cold or drought. We also found that 33% of all Arabidopsis LEA protein encoding genes are arranged in tandem repeats and that 43% are part of homeologous pairs. The majority of LEA proteins were predicted to be highly hydrophilic and natively unstructured, but some were predicted to be folded.ConclusionThe analyses indicate a wide range of sequence diversity, intracellular localizations, and expression patterns. The high fraction of retained duplicate genes and the inferred functional diversification indicate that they confer an evolutionary advantage for an organism under varying stressful environmental conditions. This comprehensive analysis will be an important starting point for future efforts to elucidate the functional role of these enigmatic proteins.
Highlights
LEA proteins have first been described about 25 years ago as accumulating late in plant seed development
According to the appearance of different sequence motifs/patterns or biased amino acid composition, plant LEA proteins have been separated into different groups [4,5,6,7]
No unifying concept for their physiological role(s) and modes of action has been attained so far. This is in part due to the fact that research has been fragmented between different species, different groups of LEA proteins and different experimental approaches
Summary
LEA (late embryogenesis abundant) proteins have first been described about 25 years ago as accumulating late in plant seed development They were later found in vegetative plant tissues following environmental stress and in desiccation tolerant bacteria and invertebrates. Late embryogenesis abundant proteins (LEA proteins) were first found in cotton (Gossypium hirsutum) seeds, accumulating late in embryogenesis [1] They were subsequently found in the seeds of many other plants, and in vegetative organs, especially under stress conditions such as cold, drought, or high salinity (see [2,3] for reviews). A strong induction of LEA gene expression has been found in the desiccation tolerant resurrection plant Craterostigma plantagineum during slow drying [23] These and many other examples in the literature suggest that LEA proteins may be important determinants of cellular dehydration tolerance in a variety of organisms from bacteria to plants and lower animals
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