Reference "Mendel's green cotyledon gene encodes a positive regulator of the chlorophyll-degrading pathway"

Reference ID

11671

Title

Mendel's green cotyledon gene encodes a positive regulator of the chlorophyll-degrading pathway

Source

Proceedings of the National Academy of Sciences of the United States of America, 2007, vol. 104, pp. 14169-14174

Authors (5)

Sato-Y	Morita-R
Nishimura-M	Yamaguchi-H
Kusaba-M

Abstract

Mutants that retain greenness of leaves during senescence are known as "stay-
green" mutants. The most famous stay-green mutant is Mendel's green cotyledon
pea, one of the mutants used in determining the law of genetics. Pea plants
homozygous for this recessive mutation (known as i at present) retain greenness
of the cotyledon during seed maturation and of leaves during senescence. We
found tight linkage between the I locus and stay-green gene originally found in
rice, SGR. Molecular analysis of three i alleles including one with no SGR
expression confirmed that the I gene encodes SGR in pea. Functional analysis of
sgr mutants in pea and rice further revealed that leaf functionality is lowered
despite a high chlorophyll a (Chl a) and chlorophyll b (Chl b) content in the
late stage of senescence, suggesting that SGR is primarily involved in Chl
degradation. Consistent with this observation, a wide range of Chl-protein
complexes, but not the ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco)
large subunit, were shown to be more stable in sgr than wild-type plants. The
expression of OsCHL and NYC1, which encode the first enzymes in the degrading
pathways of Chl a and Chl b, respectively, was not affected by sgr in rice. The
results suggest that SGR might be involved in activation of the Chl-degrading
pathway during leaf senescence through translational or posttranslational
regulation of Chl-degrading enzymes.