Characterization of photomorphogenic responses and signaling cascades controlled by phytochrome-A expressed in different tissues

Kirchenbauer, Daniel and Viczián, András and Ádám, Éva and Hegedűs, Zoltán and Klose, Cornelia and Leppert, Michael and Hiltbrunner, Andreas and Kircher, Stefan and Schäfer, Eberhard and Nagy, Ferenc (2016) Characterization of photomorphogenic responses and signaling cascades controlled by phytochrome-A expressed in different tissues. New Phytologist, 211 (2). pp. 584-598. ISSN 0028-646X

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Abstract

The photoreceptor phytochrome A acts as a light-dependent molecular switch and regulates responses initiated by very low fluences of light (VLFR) and high fluences (HIR) of far-red light. PhyA is expressed ubiquitously, but how phyA signaling is orchestrated to regulate photomorphogenesis is poorly understood. To address this issue, we generated transgenic Arabidopsis thaliana phyA-201 mutant lines expressing the biologically active phyA-YFP photoreceptor in different tissues, and analyzed the expression of several reporter genes, including ProHY5:HY5-GFP and Pro35S:CFP-PIF1, and various FR-HIR-dependent physiological responses. We show that phyA action in one tissue is critical and sufficient to regulate flowering time and root growth; control of cotyledon and hypocotyl growth requires simultaneous phyA activity in different tissues; and changes detected in the expression of reporters are not restricted to phyA-containing cells. We conclude that FR-HIR-controlled morphogenesis in Arabidopsis is mediated partly by tissue-specific and partly by intercellular signaling initiated by phyA. Intercellular signaling is critical for many FR-HIR induced responses, yet it appears that phyA modulates the abundance and activity of key regulatory transcription factors in a tissue-autonomous fashion.

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