Chlorophyll (Chl) is an essential molecule for harvesting light energy in photosynthetic organisms. We isolated yellow leaf 3 (yl3), a rice Chl-deficient mutant, which showed yellow leaves with decreased Chl content and abnormal chloroplast development. Positional cloning revealed that YL3 encodes OsCHLH, a subunit of magnesium-chelatase. In yl3, one amino acid substitution occurs at the C-terminal region of a highly conserved amino acid residue. YL3 is constitutively expressed in all tissues. Compared with the wild type, yl3 was found to be sensitive to low temperature. The expression levels of genes for Chl biosynthesis, photosynthesis and chloroplast development were strongly reduced in yl3. These results provide novel insights regarding how rice chloroplast development and Chl synthesis are regulated by YL3.

叶绿素（Chl）是在光合生物中收集光能的重要分子。我们分离了水稻Chl缺失型突变体黄叶3（yl3），显示出黄叶中Chl含量降低和叶绿体发育异常。位置克隆表明，YL3编码OsCHLH（镁螯合酶的亚基）。在yl3中，一个氨基酸取代发生在高度保守的氨基酸残基的C-末端区域。YL3在所有组织中组成性表达。与野生型相比，yl3被发现对低温敏感。在yl3中，用于Ch1生物合成，光合作用和叶绿体发育的基因的表达水平大大降低。这些结果提供了关于水稻叶绿体发育和Chl合成如何受到YL3调控的新见解。