Carboxylate clamp type tetratricopeptide repeat protein that may act as a potential Hsp90/Hsp70 co-chaperone (PubMed:20856808). Contributes to polar growth of root hairs (PubMed:28096376). A number of isoforms are produced. Up-regulated by abscisic acid treatment, and by cold and salt stress. Phox1, phox3 and phox4 triple mutants and phox1, phox2, phox3 and phox4 quadruple mutants show a 70% reduction in root hair growth (PubMed:28096376).