A conditionally fertile coi1 allele indicates cross-talk between plant hormone signalling pathways in Arabidopsis thaliana seeds and young seedlings

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 coil-16. Comparisons with coil-1 and jarl-1 plants indicated that coil-16 was only slightly more sensitive to JA than coil-1 plants. However, whilst coil-16 plants failed to produce viable pollen at 22 degreesC, they were fertile at 16 degreesC. Therefore, unlike the other coil mutants, coil-16 could be maintained as a pure line and did not require selection. We have used coil-16 seeds to define novel interactions between JA and other hormone signalling pathways in seed germination and in the development of young seedlings.