FIN219/JAR1 and cryptochrome1 antagonize each other to modulate photomorphogenesis under blue light in <i>Arabidopsis</i>

<div><p>Plant development is affected by the integration of light and phytohormones, including jasmonates (JAs). To address the molecular mechanisms of possible interactions between blue light and JA signaling in <i>Arabidopsis thaliana</i>, we used molecular and transgenic approaches to understand the regulatory relationships between FAR-RED INSENSITIVE 219 (FIN219)/JASMONATE RESISTANT1 (JAR1) and the blue-light photoreceptor cryptochrome1 (CRY1). <i>FIN219</i> overexpression in the wild type resulted in a short-hypocotyl phenotype under blue light. However, <i>FIN219</i> overexpression in <i>cry1</i>, <i>cry2</i> and <i>cry1cry2</i> double mutant backgrounds resulted in phenotypes similar to their respective mutant backgrounds, which suggests that FIN219 function may require blue light photoreceptors. Intriguingly, <i>FIN219</i> overexpression in transgenic plants harboring ectopic expression of the C terminus of CRY1 (GUS-CCT1), which exhibits a hypersensitive short-hypocotyl phenotype in all light conditions including darkness, led to a rescued phenotype under all light conditions except red light. Further expression studies showed mutual suppression between FIN219 and CRY1 under blue light. Strikingly, <i>FIN219</i> overexpression in <i>GUS-CCT1</i> transgenic lines (<i>FIN219-OE/GUS-CCT1</i>) abolished GUS-CCT1 fusion protein under blue light, whereas GUS-CCT1 fusion protein was stable in the <i>fin219-2</i> mutant background (<i>fin219-2/GUS-CCT1</i>). Moreover, FIN219 strongly interacted with COP1 under blue light, and methyl JA (MeJA) treatment enhanced the interaction between FIN219 and GUS-CCT1 under blue light. Furthermore, FIN219 level affected <i>GUS-CCT1</i> seedling responses such as anthocyanin accumulation and bacterial resistance under various light conditions and MeJA treatment. Thus, FIN219/JAR1 and CRY1 antagonize each other to modulate photomorphogenic development of seedlings and stress responses in Arabidopsis.</p>