Abstract
Phytosulfokine (PSK) is a sulfated peptide hormone involved in plant cell proliferation and differentiation. Zinnia cultured cells biosynthesize PSK that stimulates tracheary element (TE) differentiation. Time of requirement for PSK during TE differentiation was from the 24th to 36th hour of culture, before which ZePSK1 gene expression was induced by wounding. Any inhibitor of PSK signaling has not been discovered but should be a useful tool for PSK physiology. Considering that desulfated PSK is inactive, an inhibitor of tyrosine O-sulfation might be promising. Chlorate, a potent inhibitor of protein sulfation, suppressed TE differentiation and the suppression was overcome by exogenous PSK. Expression of marker genes was investigated under the presence of chlorate and PSK. Chlorate changed expression of wound-responsible genes from transient to continuous pattern, while PSK suppressed wound-induced gene expression. These results suggest that wound healing by PSK is prerequisite for TE differentiation.
