Mendel's green cotyledon gene encodes a positive regulator of the chlorophyll-degrading pathway
Mendel's green cotyledon gene encodes a positive regulator of the chlorophyll-degrading pathway
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DOI：
10.1073/pnas.0705521104
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发表时间：
2007-08-28
影响因子：
11.1
通讯作者：
Kusaba, Makoto
中科院分区：
文献类型：
--
作者：
Sato, Yutaka;Morita, Ryouhei;Kusaba, Makoto
在衰老过程中保持叶片绿色的突变体被称为“保绿”突变体。最著名的保绿突变体是孟德尔的绿子叶豌豆，这是决定遗传规律的突变体之一。对于这种隐性突变的纯合子豌豆植株(目前称为I)在种子成熟期间保持子叶的绿色，在衰老期间保持叶片的绿色。我们发现I基因座与最初在水稻SGR中发现的保绿基因紧密连锁。对3个I等位基因(包括1个不表达SGR的等位基因)的分子分析证实，I基因编码豌豆的SGR。对豌豆和水稻sgr突变体的功能分析进一步表明，尽管在衰老后期叶片中的叶绿素a和b含量较高，但叶片的功能却降低了，这表明sgr主要参与了chI的降解。与此一致的是，在SGR中，广泛的Chl蛋白复合体比野生型植物更稳定，而不是核酮糖-1，5-二磷酸羧化酶/加氧酶(Rubisco)大亚基。在水稻中，编码CHIa和CHIb降解途径第一酶的OsCHL和NYC1的表达不受SGR的影响。这些结果表明，SGR可能通过对Chl降解酶的翻译或翻译后调节参与了叶片衰老过程中CHI降解途径的激活。
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 (Chi a) and chlorophyll b (Chi b) content in the late stage of senescence, suggesting that SGR is primarily involved in Chi 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 Chi a and Chi b, respectively, was not affected by sgr in rice. The results suggest that SGR might be involved in activation of the Chi-degrading pathway during leaf senescence through translational or posttranslational regulation of Chl-degrading enzymes.