Nitric oxide responses in Arabidopsis hypocotyls are mediated by diverse phytohormone pathways

[EN] Plants are often exposed to high levels of nitric oxide (NO) that affects development and stress-triggered responses. However, the way in which plants sense NO is still largely unknown. Here we combine the analysis of early changes in the transcriptome of plants exposed to a short acute pulse of exogenous NO with the identification of transcription factors (TFs) involved in NO sensing. The NO-responsive transcriptome was enriched in hormone homeostasis and signaling-related genes. To assess events involved in NO sensing in hypocotyls, we used a functional sensing assay based on the NO-induced inhibition of hypocotyl elongation in etiolated seedlings. Hormone-related mutants and the TRANSPLANTA collection of transgenic lines conditionally expressing Arabidopsis TFs were screened for NO-triggered hypocotyl shortening. These approaches allowed the identification of hormone-related TFs, ethylene perception and signaling, strigolactone biosynthesis and signaling, and salicylate production and accumulation that are essential for or modulate hypocotyl NO sensing. Moreover, NO inhibits hypocotyl elongation through the positive and negative regulation of some abscisic acid (ABA) receptors and transcripts encoding brassinosteroid signaling components thereby also implicating these hormones in NO sensing.This work was supported by grants BIO2014-56067-P and BIO2017-82945-P from the Spanish Ministry of Economy, Industry and Competitiveness and FEDER funds. We thank the Genomics Unit of the Centro Nacional de Biotecnologia (CNB-CSIC, Madrid, Spain) for microarray processing. We gratefully acknowledged the kind donation of mutant seeds: Roberto Solano and Andrea Chini (CNB, Madrid, Spain) for the jaz and myc mutants; Paul Verslues (Institute of Plant and Microbial Biology, Academia Sinica, Taiwan) for the hai mutants; Javier Agusti, Pablo Tornero, and Pedro Rodriguez (IBMCP, Valencia, Spain) for the max, sid2eds5nahG, and pyr/pyl mutants, respectively; and Hiroaki Fujii (University of Turku, Finland) for the snrk2.3 and 2.9 mutants.Castillo López Del Toro, MC.; Coego Gonzalez, A.; Costa-Broseta, Á.; Leon Ramos, J. (2018). Nitric oxide responses in Arabidopsis hypocotyls are mediated by diverse phytohormone pathways. Journal of Experimental Botany. 69(21):5265-5278. https://doi.org/10.1093/jxb/ery28652655278692