Phytosulfokine-α, a sulfated pentapeptide, stimulates the proliferation of rice cells by means of specific high- and low-affinity binding sites

摘要

Peptide growth factors were isolated from conditioned medium derived from rice (Oryza sativa L.) sus- pension cultures and identified to be a sulfated pentapeptide [H-Tyr(SO_3H)-Ile-Tyr(SO_3H)-Thr-Gln-OH] and its C- terminal-truncated tetrapeptide [H-Tyr(SO_3H)-Ile- Tyr(SO_3H)-Thr-OH]. These structures were identical to the phytosulfokines originally found in asparagus (Asparagus officinalis L.) mesophyll cultures. The pentapeptide [phyto- sulfokine-α (PSK-α)] very strongly stimulated colony forma- tion of rice protoplasts at concentrations above 10~-8 M, indicating a similar mode of action in rice of phytosulfokines.