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

718 / 2019-05-09 11:31:26

Phytochrome signaling and the control of chloroplast biogenesis

phytochrome,light signaling,photomorphogenesis,chloroplast development

Plenary track > Photobiology

Phytochromes are red and far-red photoreceptors that regulate every facet of plant development and growth. When seedlings emerge from the soil and encounter light for the first time, phytochromes trigger a developmental transition from a dark-grown program called skotomorphogenesis to a light-dependent program called photomorphogenesis. The photomorphogenetic program enables the biogenesis of photosynthetically-active chloroplasts. Chloroplast biogenesis requires the activation of photosynthesis-associated genes encoded by both the nuclear and plastidial genomes. It is well understood that light triggers the translocation of phytochromes from the cytoplasm to the nucleus to activate photosynthesis-associated nuclear-encoded genes, but how phytochromes control the expression of photosynthesis-associated plastid-encoded genes (PhAPGs) remains elusive. PhAPGs are transcribed by a bacterial-type plastid-encoded RNA polymerase (PEP). Our genetic studies on phytochrome signaling have serendipitously revealed that phytochrome signaling and the PEP are connected by a dual-targeted nuclear/plastidial protein named HEMERA (HMR). While nuclear HMR is a transcriptional activator required for phytochrome signaling, plastidial HMR is a PEP-associated protein essential for PhAPG expression. In my talk, I will discuss our latest work on the mechanistic link between phytochrome signaling and the regulation of plastidial transcription.