The 30th International Conference on Arabidopsis Research (ICAR 2019)

472 / 2019-02-27 20:15:13

Re-discovering PHY photobiology: multiple novel phytochrome interactions and role for PHYE in FR response

Phytochrome, LUC reporter, Far Red light, PHYE

Plenary track > Photobiology

Phytochromes are important for regulation of plant growth, for instance, by controlling stability of PIF transcription factors. The transcriptional regulation of all five Phytochrome genes of Arabidopsis was investigated using PHY-LUC reporter constructs in wild-type and all individual single phy-mutant backgrounds (total 36 combinations). Analysis of the different PHY-LUC activities revealed substantial interaction at transcription level between the PHY genes in seedlings. However, most of these transcriptional interactions were no longer observed in mature rosette plants. PHYD is shown to be a constitutive repressor of PHYA transcription. Moreover, we discovered a very strong FR-induction of PHYA-LUC and PHYB-LUC in 3-day old light germinated seedlings with different dynamics, while no induction is observed in dark germinated seedlings. FR-induction of PHYA/B is also observed in mature rosette plants. Moreover, this FR induction of PHYA/B-LUC is not dependent on the classic FR-sensor PHYA. In contrast, FR-induction of PHYA is dependent on PHYE, while the FR-induction of PHYB is partially dependent on PHYB and PHYE. Finally, we show that the transcriptional response of PHY genes to different shade conditions is dependent on the order in which the light treatments are given.