Proteins encoded by A. thaliana genes At1g21670 and At4g01870 - possible participants of signal transmission phytohormone ABA

Investigation of the mechanisms of plant tolerance to stressful environments is one of thefundamental trends in plant physiology that has important applications. Abscisic acid (ABA)plays a key role in regulating the mechanisms of resistance to a wide range of environmentalstresses, as well as to biopathogenic. ABA is responsible for resistance to drought, high salinityand cold stress, thus allowing plants to colonize ecological niches where water availabilityis extremely limited or variable. The discovery in recent years completely new regulatory proteinsthat play a key role in signaling of ABA provided a major breakthrough in understandingthe signaling of this hormone, but its picture is still not complete. Thus further search of actorsinvolved in the signaling system of the hormone is promising and important problem.We have previously described two genes of A. thaliana At1g21670 and At4g01870.Using bioinformatics analysis was shown that they encoded proteins containing tryptophan-,proline- and aspartate-rich PD40 repeats, which form the conservative betapropellerdomain. This structure can serve as a platform for the assembly of multysubunitprotein complexes.The methods were used: analysis of genome-scale DNA microarray Affimetrix 25k usingMicroarray Expression Search. Web-based interface of this programm is placed on TAIR(http://arabidopsis.org) - an international scientific web-resource dedicated to research amodel plant A. thaliana. Also to study the expression of these genes at the protein level Westernblot with polyclonal antibodies against homologous protein from L. luteus was used.As a result of Affimetrix 25k DNA-microarray data processing was found that changes inAt1g21670 and At4g01870 gene expression associated with embryogenesis and early stagesof development of A. thaliana seedlings, with the effect of cold stress, salinity. The most strikingeffect on the expression of the studied genes was in case of salt and cold stress.Western blotting was performed to confirm the effect of these factors on the expressionof studied genes at the protein level. Because of the high similarity of amino acidsequences of proteins encoded by At1g21670, At4g01870 and a homologous protein fromyellow lupine antibodies used in Western-blot have cross-species activity. Indeed, onblots using these antibodies we were able to detect a clear signal of the expected valuesof molecular weight (73-77 kDa) for protein products of genes At1g21670 andAt4g01870. The signal is amplified in response to salinity and cold treatment, as well asin response to the pretreatment of A. thaliana plants with abscisic acid.The data obtained on expression of A. thaliana genes At1g21670 and At4g01870 at thelevel of mRNA and protein - transcription and translation level increase under the influenceof ABA and abiotic stress - provide further evidence of the previously suggested hypothesis ofthe involvement protein products of studied genes in ABA signaling. In addition, data obtainedin our laboratory using insertional mutants of the genes studied (data not shown, as are thesubject of a separate publication) also support this hypothesis.

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