Plant development is regulated by both extrinsic factors, including light, and intrinsic factors such as genetics and phytohormones. We use Arabidopsis seedlings as a model system to study the integration of light- and multiple hormones-mediated signalings, leading to photomorphogenic development. FIN219/JAR1, a jasmonate conjugating enzyme that belongs to a GH3 gene family in Arabidopsis, has been shown to participate in phytochrome A (phyA)-mediated far-red (FR) light signaling and can be induced by auxin and jasmonate. FIN219 as an extragenic suppressor of COP1 can interact with different partners to regulate hypocotyl elongation under far-red light condition. Ectopic expression of different domains of FIN219 in wild-type Columbia shows that the N- and C-terminal domains have an opposite effect on photomorphogenic development. Furthermore, our data reveal that the fin219 mutant affects the levels of COP1 and HY5 specifically under FR, but not other light conditions. COP1 and HY5 interact in the dark, resulting in the degradation of HY5 and leading to a skotomorphogenesis with long hypocotyls and closed cotyledons. In contrast, in the light, COP1 exclusively moves to the cytoplasm and releases HY5 from repression, giving rise to a photomorphogenic development with short hypocotyls, open cotyledons and light responsive gene expression. How the FIN219/JAR1 expression affects the regulation of COP1 and HY5 interaction relationship remains to be elucidated. How jasmonate signaling mediated by FIN219/JAR1 modulates the photomorphogenesis involving COP1 and HY5 regulatory relation is also intriguing. Thus, we plan to use molecular genetics, cell biology and microarray approaches to dissect the functional role of FIN219/JAR1 in the crosstalk between FR light and jasmonate signaling pathways. 

A model of FIN219/JAR1 functions in the photomorphogenic development of Arabidopsis seedlings under far-red light.

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