Double Mutant Analysis with the Large Flower Mutant, , to Explore the Regulatory Network Controlling the Flower and Seed Sizes in .

Two growth processes, cell proliferation and expansion, determine plant species-specific organ sizes. A large flower mutant in , (), was isolated from a mutant library. In the flowers, post-mitotic cell expansion and endoreduplication of nuclear DNA were promoted. The whole-genome resequencing and genetic analysis results showed that the loss of function in (), a mediator complex subunit, was responsible for the large flower phenotypes exhibited by . A phenotypic analysis of the mutant alleles in and the double mutants created by crossing with representative large flower mutants revealed that MED16 and MED25 share part of the negative petal size regulatory pathways. Furthermore, the double mutant analyses suggested that there were genetically independent pathways leading to cell size restrictions in the floral organs which were not related to the MED complex. Several double mutants also formed larger and heavier seeds than the wild type and single mutant plants, which indicated that MED16 was involved in seed size regulation. This study has revealed part of the size-regulatory network in flowers and seeds through analysis of the mutant, and that the size-regulation pathways are partially different between floral organs and seeds.