Abstract
In a screen for delayed floral organ abscission in Arabidopsis, we have identified a novel mutant of CORONATINE INSENSITIVE 1 (COI1), the F-box protein that has been shown to be the jasmonic acid (JA) co-receptor. While JA has been shown to have an important role in senescence, root development, pollen dehiscence and defense responses, there has been little focus on its critical role in floral organ abscission. Abscission, or the detachment of organs from the main body of a plant, is an essential process during plant development and a unique type of cell separation regulated by endogenous and exogenous signals. Previous studies have indicated that auxin and ethylene are major plant hormones regulating abscission; and here we show that regulation of floral organ abscission is also controlled by jasmonic acid in Arabidopsis thaliana. Our characterization of coi1-1 and a novel allele (coi1-37) has also revealed an essential role in apical dominance and floral meristem arrest. In this study we provide genetic evidence indicating that delayed abscission 4 (dab4-1) is allelic to coi1-1 and that meristem arrest and apical dominance appear to be evolutionarily divergent functions for COI1 that are governed in an ecotype-dependent manner. Further characterizations of ethylene and JA responses of dab4-1/coi1-37 also provide new information suggesting separate pathways for ethylene and JA that control both floral organ abscission and hypocotyl growth in young seedlings. Our study opens the door revealing new roles for JA and its interaction with other hormones during plant development.
Highlights
We demonstrate that DAB4/CORONATINE INSENSITIVE 1 (COI1) has additional roles in plant development including apical dominance and meristem arrest
Scanning electron microscopy (SEM) of the revealed fracture plane shows that cellular changes such as rounding and elongation of the cells are normal in the dab4-1 mutants, but that the timing of these changes is delayed (Figure 1B)
Scientists recognize that ethylene promotes abscission, while auxin delays this process [1,2,3,4,5,6,7,8]; the role of jasmonic acid during this process is often overlooked
Summary
Just as the falling blossoms of the peach tree provided new insights to the Zen Master Dogen, it has been the prominent delayed abscission phenotype of coronatine insensitive 1–37 (coi1-37) that is providing novel insights to basic plant development. Abscission is a cell separation process where unwanted organs such as flower petals, sepals, and filaments are often shed after fertilization while pollen, seeds, fruits, and leaflets are shed in response to developmental cues or environmental conditions including pathogen attack or stresses [1,2]. Both exogenous and endogenous signals regulate abscission. We demonstrate that DAB4/COI1 has additional roles in plant development including apical dominance and meristem arrest
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