Peptide growth factor phytosulfokine-alpha contributes to the pollen population effect

Planta. 2000 Oct;211(5):752-5. doi: 10.1007/s004250000370.


Density-dependent pollen germination and tube growth in vitro is a well-documented phenomenon, termed the pollen population effect, but far less is known about its molecular basis. We present evidence to support phytosulfokine-alpha [Y(SO3H)IY(SO3H)TQ; PSK-alpha] as a native bioactive factor contributing to this effect. Mature pollen grains of Nicotiana tabacum L. var. macrophylla were incubated in liquid medium for 2 h. Pollen germination frequency increased in a density-dependent manner from 625 to 46,000 grains/ml. Conditioned medium, obtained from the medium of pollen cultured at a density of 10,000 pollen grains/ml for 12 h, promoted the germination of pollen cultured at a low density (625 grains/ml). A rabbit antiserum against PSK-alpha specifically inhibited the promotive effect of conditioned medium. Quantification by enzyme-linked immunosorbent assay showed that the conditioned medium contained 0.4 nM of PSK-alpha. Exogenous PSK-alpha also stimulated pollen germination in the low-density culture. These results indicate that PSK-alpha is an important regulator involved in the pollen population effect.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cells, Cultured
  • Culture Media, Conditioned
  • Kinetics
  • Peptide Hormones
  • Plant Growth Regulators / pharmacology
  • Plant Growth Regulators / physiology*
  • Plant Proteins / pharmacology
  • Plant Proteins / physiology*
  • Plants, Toxic*
  • Pollen / cytology
  • Pollen / drug effects
  • Pollen / physiology*
  • Tobacco / cytology
  • Tobacco / physiology*


  • Culture Media, Conditioned
  • PSK-alpha protein, plant
  • Peptide Hormones
  • Plant Growth Regulators
  • Plant Proteins