Stigma receptivity with pollen in sunflower accompanies novel histochemical and biochemical changes in both male and female reproductive structures

Abstract

Pollen–pistil interaction is one of the widely studied cell–cell communication events in angiosperms. Pollination of the receptive pistil with compatible pollen and the subsequent steps that determines the success of fertilization depend on the cooperative events between pollen and pistil. Before the onset of these interactive events between pollen and pistil, both the participants prepare themselves for the upcoming complex cellular events. Receptive surface of stigma is characterized by the accumulation of reactive oxygen species and expression of specific biomolecules and enzymes, such as non-specific esterases and peroxidases. Pollen grains produce nitric oxide that scavenge reactive oxygen species generated on stigma surface after pollination and just prior to pollen germination. Present work reports accumulation of glycoproteins, lipids and phospholipids at the base of stigmatic papillae in mature receptive stigma. A 31 kDa glycoprotein has been detected in stigma homogenate. Stigma exhibit enhanced expression of peroxidase isoforms relative to buffer soluble fractions of pollen, i.e. intact pollen, internal pollen and tryphine fractions. A 54 kDa protease is expressed in pollen grains as well as stigma. Biochemical analyses of these biomolecules in pollen and stigma relative to other vegetative (corolla of ray and disc floret, bracts, young leaves) and reproductive (anther wall and ovary) parts highlight the implications of these biomolecules in pollen–stigma interaction.