Reference "Rice NON-YELLOW COLORING1 Is Involved in Light-Harvesting Complex II and Grana Degradation during Leaf Senescence"

Reference ID

11547

Title

Rice NON-YELLOW COLORING1 Is Involved in Light-Harvesting Complex II and Grana Degradation during Leaf Senescence

Source

The Plant cell, 2007, vol. , pp. -

Authors (11)

Kusaba-M	Ito-H	Morita-R	Iida-S
Sato-Y	Fujimoto-M	Kawasaki-S	Tanaka-R
Hirochika-H	Nishimura-M	Tanaka-A

Abstract

Chlorophyll degradation is an aspect of leaf senescence, which is an active
process to salvage nutrients from old tissues. non-yellow coloring1 (nyc1) is a
rice (Oryza sativa) stay-green mutant in which chlorophyll degradation during
senescence is impaired. Pigment analysis revealed that degradation of not only
chlorophylls but also light-harvesting complex II (LHCII)-bound carotenoids was
repressed in nyc1, in which most LHCII isoforms were selectively retained during
senescence. Ultrastructural analysis of nyc1 chloroplasts revealed that large
and thick grana were present even in the late stage of senescence, suggesting
that degradation of LHCII is required for the proper degeneration of thylakoid
membranes. Map-based cloning of NYC1 revealed that it encodes a chloroplast-
localized short-chain dehydrogenase/reductase (SDR) with three transmembrane
domains. The predicted structure of the NYC1 protein and the phenotype of the
nyc1 mutant suggest the possibility that NYC1 is a chlorophyll b reductase.
Although we were unable to detect the chlorophyll b reductase activity of NYC1,
NOL (for NYC1-like), a protein closely related to NYC1 in rice, showed
chlorophyll b reductase activity in vitro. We suggest that NYC1 and NOL encode
chlorophyll b reductases with divergent functions. Our data collectively suggest
that the identified SDR protein NYC1 plays essential roles in the regulation of
LHCII and thylakoid membrane degradation during senescence.