Jasmonates (JAs) regulate Arabidopsis thaliana (L.) Heynh. wound and defense responses, pollen development, and stress-related growth inhibition. Significantly, each of these responses requires COI1, an F-box protein. We fused firefly luciferase as a reporter to the JA-responsive promoter for the vegetative storage protein gene (VSP) and used this to screen for mutants that failed to express luciferase in the presence of JA, isolating a mutant designated coi1-16. Comparisons with coi1-1 and jar1-1 plants indicated that coi1-16 was only slightly more sensitive to JA than coi1-1 plants. However, whilst coi1-16 plants failed to produce viable pollen at 22 °C, they were fertile at 16 °C. Therefore, unlike the other coi1 mutants, coi1-16 could be maintained as a pure line and did not require selection. We have used coi1-16 seeds to define novel interactions between JA and other hormone signalling pathways in seed germination and in the development of young seedlings.