A knockdown mutation of YELLOW-GREEN LEAF2 blocks chlorophyll biosynthesis in rice
A knockdown mutation of YELLOW-GREEN LEAF2 blocks chlorophyll biosynthesis in rice
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DOI：
10.1007/s00299-013-1498-y
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发表时间：
2013-12-01
影响因子：
6.2
通讯作者：
Jiang, Ling
中科院分区：
文献类型：
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作者：
Chen, Hong;Cheng, Zhijun;Jiang, Ling
编码血红素加氧酶1的黄绿色LEAF2的插入突变导致其转录水平显著降低，从而损害水稻的叶绿素生物合成。高等植物中的血红素加氧酶(HO)催化血红素的降解合成光敏色素前体，其在水稻开花过程中的光周期调控作用已被揭示。然而，它在调节水稻叶绿素(Chl)合成中的作用还没有得到充分的研究。在这项研究中，我们从Co-60辐射的群体中分离到一个名为黄绿叶2(Ygl2)的水稻突变体。正常生长的Ygl2幼苗叶片呈黄绿色，Chl和四氢吡咯中间体含量降低，Chla/b比值增加。超微结构分析表明，ygl2突变体中基粒堆积不良，导致叶绿体发育不良。将ygl2基因定位在6号染色体上，通过图位克隆的方法进行分离。序列分析表明，该基因编码水稻HO1基因，并通过转基因互补试验和RNA干扰验证了其同源性。在YGL2/HO1的第一个外显子上发现了一个7kb的插入，导致YGL2突变体的YGL2表达显著降低。YGL2在多种水稻组织中都有结构性表达，其中以叶片中的表达水平最高，并受温度的调节。此外，我们还发现一些与Chl生物合成和光合作用相关的基因在ygl2突变体中的表达水平同时发生了变化。这些结果为YGL2在水稻Chl生物合成中起重要作用提供了直接证据。
An insert mutation of YELLOW - GREEN LEAF2 , encoding Heme Oxygenase 1 , results in significant reduction of its transcript levels, and therefore impairs chlorophyll biosynthesis in rice.Heme oxygenase (HO) in higher plants catalyzes the degradation of heme to synthesize phytochrome precursor and its roles conferring the photoperiodic control of flowering in rice have been revealed. However, its involvement in regulating rice chlorophyll (Chl) synthesis is not fully explored. In this study, we isolated a rice mutant named yellow-green leaf 2 (ygl2) from a Co-60-irradiated population. Normal grown ygl2 seedlings showed yellow-green leaves with reduced contents of Chl and tetrapyrrole intermediates whereas an increase of Chl a/b ratio. Ultrastructural analyses demonstrated grana were poorly stacked in ygl2 mutant, resulting in underdevelopment of chloroplasts. The ygl2 locus was mapped to chromosome 6 and isolated via map-based cloning. Sequence analysis indicated that it encodes the rice HO1 and its identity was verified by transgenic complementation test and RNA interference. A 7-Kb insertion was found in the first exon of YGL2/HO1, resulting in significant reduction of YGL2 expressions in the ygl2 mutant. YGL2 was constitutively expressed in a variety of rice tissues with the highest levels in leaves and regulated by temperature. In addition, we found expression levels of some genes associated with Chl biosynthesis and photosynthesis were concurrently altered in ygl2 mutant. These results provide direct evidence that YGL2 has a vital function in rice Chl biosynthesis.