Recent identification of NYE1/SGR1 brought up a new era for the exploration of the regulatory mechanism of Chlorophyll （Chl） degradation. Cluster analysis of senescence associated genes with putative chloroplast targeting sequences revealed several genes sharing a similar expression pattern with NYE1. Further characterization of available T-DNA insertion lines led to the discovery of a novel stay-green gene CRN1 （Co-regulated with NYE1）. Chl breakdown was significantly restrained in crnl-1 under diversified senescence scenarios, which is comparable with that in acdl-20, but much more severe than that in nyel- 1. Notably, various Chl binding proteins, especially trimeric LHCP II, were markedly retained in crnl-1 four days after dark-treatment, possibly due to a lesion in disassociation of protein-pigment complex. Nevertheless, the photochemical efficiency of PSII in crnl-1 declined, even more rapidly, two days after dark-treatment, compared to those in Col-0 and nyel-1. Our results suggest that CRN1 plays a crucial role in Chl degradation, and that loss of its function produces various side-effects, including those on the breakdown of Ch-protein complex and the maintenance of the residual photosynthetic capability during leaf senescence.
