State Key Laboratory for Conservation and Utilization of Subtropical Agro Bioresources, College of Life Science and Technology, Guangxi University, Nanning 530004, China.
State Key Laboratory for Conservation and Utilization of Subtropical Agro Bioresources, College of Life Science and Technology, Guangxi University, Nanning 530004, China.
Plant Sci. 2024 Aug;345:112134. doi: 10.1016/j.plantsci.2024.112134. Epub 2024 May 27.
Oryza longistaminata (OL), an AA-genome African wild rice which can propagate clonally via rhizome, is an important germplasm for improvement of Asian cultivated rice, however recessive lethal alleles can hitchhike clonal propagation in heterozygous state. Selfing of OL is difficult due to its self-incompatibility, but simple selfing of hybrid progeny between OL and O. sativa is effective to disclose and eliminate recessive lethal alleles. Here, we identified an exhibited albino-lethal phenotype mutant, from an F population between OL and O. sativa, named it albino seedling-lethal (asl). The leaves of asl mutant showed abnormal chloroplast development. The albino characteristics of asl were determined to be governed by a set of recessive nuclear genes through genetic analysis. Map-based cloning experiments found that a single nucleotide variation (G to A) was detected in the exon of OsASL in OL, which causes a premature stop codon. OsASL encodes a PLS-type PPR protein with 12 pentratricopeptide repeat domains, and is translocalized to chloroplasts. Complementation and knockout transgenic experiments further confirmed that OsASL is responsible for the albino-lethal phenotype. Loss-of-function OsASL (i.e. osasl) resulted in devoid of intron splicing of chloroplast RNA atpF, ndhA, rpl2 and rps12, and also RNA editing of ndhB, but facilitates the RNA editing of rpl2 in the plastid. Transcriptome sequencing showed that OsASL was mainly involved in chlorophyll synthesis pathway. The expression of Chlorophyll-associated genes were significantly decreased in asl plants, especially PEP (plastid-encoded RNA polymerase)-mediated genes. Our results suggest that OsASL is crucial for RNA editing, RNA splicing of chloroplast RNA group II genes, and plays an essential role in chloroplast development during early leaf development in rice.
长雄野生稻（OL）是一种 AA 基因组的非洲野生稻，可通过根茎克隆繁殖，是改良亚洲栽培稻的重要种质资源，但隐性致死等位基因可以在杂合状态下随克隆繁殖而传播。OL 由于自交不亲和性而难以自交，但 OL 与 O. sativa 杂交后代的简单自交可以有效地揭示和消除隐性致死等位基因。在这里，我们从 OL 和 O. sativa 的 F1 群体中鉴定出一个表现出白化致死表型的突变体，将其命名为白化致死幼苗(asl)。asl 突变体的叶片表现出异常的叶绿体发育。通过遗传分析，asl 突变体的白化特征由一组隐性核基因控制。基于图谱的克隆实验发现，OL 中 OsASL 的外显子中检测到一个单核苷酸变异（G 到 A），导致提前终止密码子。OsASL 编码一个具有 12 个五肽重复结构域的 PLS 型 PPR 蛋白，定位于叶绿体。互补和敲除转基因实验进一步证实，OsASL 负责白化致死表型。功能丧失型 OsASL（即 osasl）导致叶绿体 RNA atpF、ndhA、rpl2 和 rps12 的内含子剪接缺失，以及 ndhB 的 RNA 编辑，但促进了质体中 rpl2 的 RNA 编辑。转录组测序显示，OsASL 主要参与叶绿素合成途径。asl 植株中叶绿素相关基因的表达显著下降，尤其是 PEP（质体编码 RNA 聚合酶）介导的基因。我们的结果表明，OsASL 对于 RNA 编辑、叶绿体 RNA 组 II 基因的 RNA 剪接以及在水稻早期叶片发育过程中叶绿体的发育至关重要。
