Light deprivation induces leaf yellowing, but the molecular mechanism of leaf yellowing regulated by light is still unknown. In darkness, intermittent pulses of red light can inhibit leaf yellowing. We revealed that in Arabidopsis, dark-induced senescence requires phytochrome-interacting transcription factors PIF4 and PIF5 (PIF4/PIF5). ELF3 and phytochrome B inhibit senescence by repressing PIF4/PIF5 at the transcriptional and post-translational levels, respectively. PIF4/PIF5 act in the signalling pathways of two senescence-promoting hormones, ethylene and abscisic acid, by directly activating expression of EIN3, ABI5 and EEL. In turn, PIF4, PIF5, EIN3, ABI5 and EEL directly activate the expression of the major senescence-promoting NAC transcription factor ORESARA1, thus forming multiple, coherent feed-forward loops. Our results reveal how classical light signalling connects to leaf yellowing in Arabidopsis.

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<Related publicatios>

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Sakuraba Y, Jeong J, Kang MY, Kim J, Paek NC, Choi G. (2014) Phytochrome-interacting transcription factors PIF4 and PIF5 induce leaf senescence in Arabidopsis. Nature Communications, 5:4636.

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Shahnejat-Bushehri S, Tarkowska D, Sakuraba Y, Balazadeh S. (2016) Arabidopsis NAC transcription factor JUB1 regulates GA/BR metabolism and signaling. Nature Plants, 2:16013.

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Sakuraba Y, Han SH, Yang HJ, Piao W, Paek NC. (2016) Mutation of Rice Early Flowering3.1 (OsELF3.1) delays leaf senescence in rice. Plant Molecular Biology 92:223-234.

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Sakuraba Y, Kanno S, Mabuchi A, Monda K, Iba K, Yanagisawa S. (2018) A phytochrome B-mediated regulatory mechanism of phosphorus acquisition. Nature Plants, 4:1089-1101

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