Predominantly Cytoplasmic Localization in Yeast of ASR1, a Non-Receptor Transcription Factor from Plants

Abstract

The Asr gene family (named after abscisic acid, stress and ripening), currently classified as a novel group of the LEA superfamily, is exclusively present in the genomes of seed plants, except for the Brassicaceae family. It is associated with water-deficit stress and is involved in adaptation to dry climates. Motivated by separate reports depicting ASR proteins as either transcription factors or chaperones, we decided to determine the intracellular localization of ASR proteins. For that purpose, we employed an in vivo eukaryotic expression system, the heterologous model Saccharomyces cerevisiae, including wild type strains as well as mutants in which the variant ASR1 previously proved to be functionally protective against osmotic stress. Our methodology involved immunofluorescence-based confocal microscopy, without artificially altering the native structure of the protein under study. Results show that, in both normal and osmotic stress conditions, recombinant ASR1 turned out to localize mainly to the cytoplasm, irrespective of the genotype used, revealing a scattered distribution in the form of dots or granules. The results are discussed in terms of a plausible dual (cytoplasmic and nuclear) role of ASR proteins.

The ZmASR1 Protein Influences Branched-Chain Amino Acid Biosynthesis and Maintains Kernel Yield in Maize under Water-Limited Conditions

“…This is not necessarily surprising, since it has been shown recently that posttranscriptional regulation can affect the protein abundance without affecting transcript levels (Bö hmer and Schroeder, 2011). These data, therefore, strengthen the idea that ZmASR1, similar to other ASR proteins, may act both as a transcriptional regulator and a chaperone-like protein protector (Saumonneau et al, 2008;Urtasun et al, 2010). A synergistic relationship was found between the osmolyte Gly betaine and the SlASR1 protein, suggesting a combined mechanism of action of these two proteins in response to abiotic stresses (Konrad and Bar-Zvi, 2008).…”

Nuclear Import and Dimerization of Tomato ASR1, a Water Stress-Inducible Protein Exclusive to Plants

“…It is possible that the nucleus pore architecture in Nicothiana benthamiana differs from that in Chenopodium quinoa or tobacco cell line BY2, which has been used as experimental models for LLA23 and VvMSA localization studies [7], [27]. Similarly, tomato ASR1 localized mainly in the cytosol when expressed in yeast [30]. It could be interesting to test whether these ASR1 homologs still need their NLS to enter the nucleus of N. benthamiana leaf epidermal cells.…”

Effects of Fe3+and Zn2+on the Structural and Thermodynamic Properties of a Soybean ASR Protein

“…23) For example, CDF (cation diffusion facilitator) proteins, which are cation efflux transporters, play essential roles in metal homeostasis. 19) Urtasun et al 24) found that the tomato ASR1 protein was predominantly localized in the cytoplasm in yeast. Shen et al 25) reported that expression of the GbAsr gene from Ginkgo biloba was up regulated a short time after the occurrence of abiotic stress.…”