Abstract
Late Embryogenesis Abundant (LEA) proteins, a group of hydrophilic proteins, have been linked to survival in plants and animals in periods of stress, putatively through safeguarding enzymatic function and prevention of aggregation in times of dehydration/heat. Yet despite decades of effort, the molecular-level mechanisms defining this protective function remain unknown. In this paper, we summarize and review research discoveries of the classification of the LEA protein groups based on their amino acid sequence similarity and on the presence of distinctive conserved motifs. Moreover, we focus on high correlation between their accumulation and water deficit, reinforcing their functional relevance under abiotic stresses. We also discuss the biochemical properties of LEA proteins arising from their hydrophilic nature and by amino acid composition. Although significant similarities have not been found between the members of the different groups, a unifying and outstanding feature of most of them is their high hydrophilicity and high content of glycine. Therefore, we have highlighted the biotechnological applications of LEA genes, and the effects of over-expressing LEA genes from all LEA groups from different species of origin into different plant hosts. Apart from agronomical purposes, LEA proteins could be useful for other biotechnological applications in relation to their capacity to prevent aggregation of proteins.
Highlights
Plants are exposed to multiple environmental stresses along their life cycle
They have been found in prokaryotes Deinococcus radiodurans [56], Haemophilus influenza [57] and in Caenorhabditis elegans (CeLEA-1), whose expression is correlated with the survival of this nematode under conditions of desiccation, osmotic, and heat stress [58]
They accumulate during seed development and they are considered as embryo-specific Late Embryogenesis Abundant (LEA) proteins [95] [96]
Summary
Plants are exposed to multiple environmental stresses along their life cycle. Abiotic stresses such as drought, high salinity and freezing temperatures affect most areas of the world and they impact in plants by directly reducing its survival in the natural environment and its productivity in agriculture. In most plants the final stage of seed development, maturation, is initiated by a reduction in seed water content, which will eventually drop to about 10% During this stage and preceded by an increase in ABA content, gene expression and protein profiles change greatly and are associated with the acquisition of desiccation tolerance and development of capacity for seed germination [21] [22]. LEA proteins accumulate in vegetative tissues exposed to dehydration, osmotic, and/or low temperature stress [5] [17] [18] [24] They are found in anydrobiotic resurrection plants upon drying [3] [25]. The correlation of LEA proteins in seed maturation stages, during water stress in vegetative plant organs, and in anydrobiotic animals suggests that LEA proteins represent a widespread adaptation to water deficit; their precise functions remain unclear
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