Regulation and Function of Pollination-Induced Ethylene in Carnation and Petunia Flowers

Abstract

In many flowers pollination accelerates ethylene biosynthesis and developmental changes observed during the natural senescence of unpollinated flowers. A burst of ethylene production from the stigma/ style is often the first detectable post-pollination event. We are interested in the nature of the pollen-pistil interaction that induces ethylene biosynthesis and the role of ethylene in triggering subsequent post-pollination phenomena including ovary development and senescence of the corolla. In carnations we have identified a pollination responsive ACC synthase that is up regulated by 1 hour after pollination in styles. We have demonstrated that the regulation of this gene by pollination is independent of ethylene action, but that ethylene action within the pollinated style is required to initiate subsequent post-pollination events in the ovary and petals. Using Petunia hybrida as a model we have shown that pollen-borne ACC is synthesized in the haploid pollen grain by a pollen specific ACC synthase gene. Using transgenic plants that fail to accumulate ACC in their pollen we have shown that pollination-induced ethylene production and ACC synthase mRNA accumulation in the style is not dependent on ACC in the pollen grain. With the identification of pollination responsive ACC synthase genes and the use of pollen that is deficient in potential elicitors it should be possible to identify the primary pollination signal in Petunia and carnation flowers.