The Arabidopsis 14-3-3 family -target protein specificity and expression of isoforms

14-3-3 proteins comprise a family of highly conserved proteins. 14-3-3 proteins have been found in all organisms examined except for members of the prokaryotic kingdom. 14-3-3s are involved in numerous processes in the cell and they typically bind to phosphorylated motifs in other proteins and regulate their activities. In plants, 14-3-3 proteins are recognized as key regulators of primary metabolism and membrane transport. In Arabidopsis, there are 15 genes coding for 14-3-3s and hence several 14-3-3 isoforms may be present simultaneously in the plant. The aim of my work has been to understand why there are so many 14-3-3 isoforms. To investigate if there is specificity in 14-3-3/target protein interaction, the H+-ATPase/14-3-3 interaction was used as a model system. The study indicated some specificity but also a wide redundancy. To further analyse the question of specificity at different levels promoter:GUS fusions were utilized. The results clearly indicate a developmental, cell-, tissue- and organ-specific expression for all of the 14-3-3 isoforms in Arabidopsis. There is not a single case where the promoter of one isoform shows an expression that is identical to the expression of another isoform.