Abstract
Homologues of the p23 co-chaperone of HSP90 are present in all eukaryotes, suggesting conserved functions for this protein throughout evolution. Although p23 has been extensively studied in animal systems, little is known about its function in plants. In the present study, the functional characterization of the two isoforms of p23 in Arabidopsis thaliana is reported, suggesting a key role of p23 in the regulation of root development. Arabidopsis p23 mutants, for either form, show a short root length phenotype with a reduced meristem length. In the root meristem a low auxin level associated with a smaller auxin gradient was observed. A decrease in the expression levels of PIN FORMED PROTEIN (PIN)1, PIN3, and PIN7, contextually to an inefficient polar localization of PIN1, was detected. Collectively these results suggest that both Arabidopsis p23 isoforms are required for root growth, in particular in the maintenance of the root meristem, where the proteins are located.
Highlights
Root growth and development are fundamental processes for the life of plants, controlling water uptake, nutrient acquisition, anchorage to soil, and secondary metabolite synthesis and storage (Saini et al, 2013)
These analyses revealed that p23 proteins are located in the root meristem, where they intervene in the regulation of root growth and development
PIN7-GFP was absent in the stele cells near the stem cell niche (Fig. 5R, S). These results demonstrate that alterations in PIN expression and localization are the most likely cause of lower auxin levels in p23 mutants, linking p23 activity to the maintenance of a correct PAT in the root meristem
Summary
Root growth and development are fundamental processes for the life of plants, controlling water uptake, nutrient acquisition, anchorage to soil, and secondary metabolite synthesis and storage (Saini et al, 2013). The difference in length of p23-1 and p23-2 reflects a glycine rich (MG/GA) segment of 70 amino acids in the C-terminal region of p23-1, whose function is not yet understood Both plant p23 isoforms and the chimeric protein p23-1-d (lacking the glycine rich tail) bind to HSP90 in vitro; unlike their animal counterpart, these proteins do not reduce the chaperone ATPase activity rate (Zhang et al, 2010). Arabidopsis p23 isoforms have been the object of previous biochemical characterization studies (Zhang et al, 2010; Tosoni et al, 2011), the physiological role of these proteins remains elusive These analyses revealed that p23 proteins are located in the root meristem, where they intervene in the regulation of root growth and development
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