title: Albino Leaf 2 is involved in the splicing of chloroplast group I and II introns in rice.
abstract: Chloroplasts play an essential role in plant growth and development through manipulating photosynthesis and the production of hormones and metabolites. Although many genes or regulators involved in chloroplast biogenesis and development have been isolated and characterized, identification of novel components is still lacking. We isolated a rice (Oryza sativa) mutant, termed albino leaf 2 (al2), using genetic screening. Phenotypic analysis revealed that the al2 mutation caused obvious albino leaves at the early developmental stage, eventually leading to al2 seedling death. Electron microscopy investigations indicated that the chloroplast structure was disrupted in the al2 mutants at an early developmental stage and subsequently resulted in the breakdown of the entire chloroplast. Molecular cloning illustrated that AL2 encodes a chloroplast group IIA intron splicing facilitator (CRS1) in rice, which was confirmed by a genetic complementation experiment. Moreover, our results demonstrated that AL2 was constitutively expressed in various tissues, including green and non-green tissues. Interestingly, we found that the expression levels of a subset of chloroplast genes that contain group IIA and IIB introns were significantly reduced in the al2 mutant compared to that in the wild type, suggesting that AL2 is a functional CRS1 in rice. Differing from the orthologous CRS1 in maize and Arabidopsis that only regulates splicing of the chloroplast group II intron, our results demonstrated that the AL2 gene is also likely to be involved in the splicing of the chloroplast group I intron. They also showed that disruption of AL2 results in the altered expression of chloroplast-associated genes, including chlorophyll biosynthetic genes, plastid-encoded polymerases and nuclear-encoded chloroplast genes. Taken together, these findings shed new light on the function of nuclear-encoded chloroplast group I and II intron splicing factors in rice.
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Provincial Key Laboratory of Plant Molecular Breeding, College of Agriculture, South China Agricultural University, Guangzhou 510642, China.
authors.forename: Changhong
authors.initials: C
authors.lastname: Liu
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Provincial Key Laboratory of Plant Molecular Breeding, College of Agriculture, South China Agricultural University, Guangzhou 510642, China.
authors.forename: Haitao
authors.initials: H
authors.lastname: Zhu
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Provincial Key Laboratory of Plant Molecular Breeding, College of Agriculture, South China Agricultural University, Guangzhou 510642, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Xing
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Provincial Key Laboratory of Plant Molecular Breeding, College of Agriculture, South China Agricultural University, Guangzhou 510642, China.
authors.forename: Jianjie
authors.initials: J
authors.lastname: Tan
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Provincial Key Laboratory of Plant Molecular Breeding, College of Agriculture, South China Agricultural University, Guangzhou 510642, China.
authors.forename: Xionghui
authors.initials: X
authors.lastname: Chen
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Provincial Key Laboratory of Plant Molecular Breeding, College of Agriculture, South China Agricultural University, Guangzhou 510642, China.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Zhang
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Provincial Key Laboratory of Plant Molecular Breeding, College of Agriculture, South China Agricultural University, Guangzhou 510642, China.
authors.forename: Haifeng
authors.initials: H
authors.lastname: Peng
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Provincial Key Laboratory of Plant Molecular Breeding, College of Agriculture, South China Agricultural University, Guangzhou 510642, China zmzhang@scau.edu.cn qjxie@scau.edu.cn.
authors.forename: Qingjun
authors.initials: Q
authors.lastname: Xie
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Provincial Key Laboratory of Plant Molecular Breeding, College of Agriculture, South China Agricultural University, Guangzhou 510642, China zmzhang@scau.edu.cn qjxie@scau.edu.cn.
authors.forename: Zemin
authors.initials: Z
authors.lastname: Zhang
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000235:genetics* / Q000502:physiology / Q000648:ultrastructure; D061125:Genes, Chloroplast / Q000235:genetics / Q000502:physiology; D007438:Introns / Q000235:genetics* / Q000502:physiology; D008854:Microscopy, Electron; D012275:Oryza / Q000235:genetics* / Q000502:physiology; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology*; D012326:RNA Splicing / Q000235:genetics / Q000502:physiology; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D010940:Plant Proteins; D002734:Chlorophyll
keywords: Albino leaf; CRS1; RNA splicing.; chloroplast development; group I intron; group II intron; rice