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7-Hydroxymethyl chlorophyll a reductase functions in metabolic channeling of chlorophyll breakdown intermediates during leaf senescence.

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Publication date 2013
Author Sakuraba Yasuhito, Kim Ye-Sol, Yoo Soo-Cheul, Hörtensteiner Stefan, Paek Nam-Chon,
Project Chlorophyll breakdown: analysis of fruit ripening, evolution and regulation
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Original article (peer-reviewed)

Journal Biochemical and Biophysical Research Communications
Volume (Issue) 430
Page(s) 32 - 37
Title of proceedings Biochemical and Biophysical Research Communications
DOI 10.1016/j.bbrc.2012.11.050

Abstract

During natural or dark-induced senescence, chlorophyll degradation causes leaf yellowing. Recent evidence indicates that chlorophyll catabolic enzymes (CCEs) interact with the photosynthetic apparatus; for example, five CCEs (NYC1, NOL, PPH, PAO and RCCR) interact with LHCII. STAY-GREEN (SGR) and CCEs interact with one another in senescing chloroplasts; this interaction may allow metabolic channeling of potentially phototoxic chlorophyll breakdown intermediates. 7-Hydroxymethyl chlorophyll a reductase (HCAR) also acts as a CCE, but HCAR functions during leaf senescence remain unclear. Here we show that in Arabidopsis, HCAR-overexpressing plants exhibited accelerated leaf yellowing and, conversely, hcar mutants stayed green during dark-induced senescence. Moreover, HCAR interacted with LHCII in in vivo pull-down assays, and with SGR, NYC1, NOL and RCCR in yeast two-hybrid assays, indicating that HCAR is a component of the proposed SGR-CCE-LHCII complex, which acts in chlorophyll breakdown. Notably, HCAR and NOL are expressed throughout leaf development and are drastically down-regulated during dark-induced senescence, in contrast with SGR, NYC1, PPH and PAO, which are up-regulated during dark-induced senescence. Moreover, HCAR and NOL are highly up-regulated during greening of etiolated seedlings, strongly suggesting a major role for NOL and HCAR in the chlorophyll cycle during vegetative stages, possibly in chlorophyll turnover.
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