Plants are exposed to effects of abiotic stress factors on a daily basis. ASR1 is a small (13 kDa) highly-charged, plant-specific protein, localised in citoplasm and nucleus, which takes part in cell's stress-defending pathways. It has a zinc-dependent DNA-binding activity – zinc enables the protein to transform from unfolded to fully folded form. It is believed that the asr genes, which we know of today, developed from a single gene family, probably through a model of concerned evolution. The evidence for that are gene duplications which took place recently (which state that asr3 originated from asr4) and homology between tomato asr4 and rice asr6 genes. Although we have much to learn about ASR1's functional and biological function, it has become clear that it's nuclear form plays role of a transcription factor, which induces a downstream of genes and signal pathways included in plant's response to abiotic stress. It is not yet known how does the cytosolic form of the protein takes part in homeostasis, but it is thought that it's transformation to folded state and transportation to the nucleus have something to do with the way this protein's activity is regulated. Nevertheless, we do now know that it's expression induces the plant's ability to tolerate damage which took place after plant's been exposed to stress. It does it so by lowering the net uptake of sodium in the cell (contribution to salt stress tolerance) and through it's role as a hydrophilin. Anyway, we've only just began to realise it's biologycal importance as a mean to construct transgenic plants which will be more tolerant to abiotic stress factors and will grow more sucessfully in new habitats.