Figure 8.

Model to Explain Differences in the Transmission Frequencies of GA-Deficient and GA-Insensitive Mutations.

Pollen carrying GA-deficient mutations, which are poorly transmitted, does not synthesize GA, which is essential for pollen tube germination and elongation, because the expression of these genes occurs after meiosis. By contrast, GA signaling functions normally in pollen carrying GA-insensitive mutations because the GA-signaling genes are actively expressed just before meiosis; therefore, their products should be transported into pollen carrying mutant alleles. +/− indicates a heterozygous genotype of pollen mother cells, whereas + and − indicate the wild-type and mutant alleles, respectively, of pollen cells. Gray shading indicates the expression of GA synthesis or GA-signaling genes in pollen mother cells or pollen.