@article{ZHANG2026, 
author = {Ye ZHANG and ChengCheng WANG and Long ZHANG},
title = {Gene Cloning and Functional Characterization of the Albino Lethal Mutant wll2 in Rice},
year = {2026},
journal = {Scientia Agricultura Sinica},
volume = {59},
number = {17},
pages = {3699-3711},
keywords = {Oryza sativa, albino lethal, MutMap+, OsDXS1, chloroplast, RNA-seq},
url = {https://www.sciopen.com/article/10.3864/j.issn.0578-1752.2026.17.001},
doi = {10.3864/j.issn.0578-1752.2026.17.001},
abstract = {ObjectiveThis study aims to investigate the regulatory mechanism of key gene in the methylerythritol phosphate (MEP) pathway on chloroplast development, chlorophyll biosynthesis, and seedling growth in rice. It seeks to elucidate the molecular mechanism underlying the albino lethal phenotype of the rice leaf color mutant, thereby providing a theoretical foundation for understanding photosynthetic mechanisms and developing germplasm with high photosynthetic efficiency.MethodThe wild-type rice variety Wuyunjing 8 and its derived albino lethal mutant wll2 (white leaf and lethal 2) were used as experimental materials. A combination of molecular biology techniques, including pigment content determination, transmission electron microscopy, MutMap+ analysis, CRISPR-Cas9 gene editing, quantitative real-time PCR (qRT-PCR), transient expression assay in tobacco leaves, transcriptome sequencing (RNA-seq), and Western blot analysis, was employed to clone the target gene and characterize its function.ResultThe wll2 mutant exhibited a distinct albino phenotype from germination, which persisted until the seedlings died at the four-leaf stage. Seedling growth was severely inhibited, with significantly reduced shoot and root lengths compared to the wild type. The mutant showed significantly lower chlorophyll a and chlorophyll b contents. Mesophyll cells of wll2 contained significantly fewer chloroplasts, with reduced and disorganized thylakoid membranes. Using MutMap+ analysis combined with gene editing, the gene responsible for the albino phenotype was identified as OsDXS1, which encodes 1-deoxy-D-xylulose-5-phosphate synthase, a key enzyme in the MEP terpenoid biosynthesis pathway. qRT-PCR analysis revealed that OsDXS1 is expressed in various rice tissues, with the highest transcript level in leaves, significantly exceeding that in roots, stems, sheaths, and young panicles. Transient expression in tobacco demonstrated that the OsDXS1 protein co-localized with chloroplast autofluorescence, confirming its chloroplast localization, consistent with its role in the MEP pathway. Transcriptome analysis identified 7197 differentially expressed genes (DEGs) between wll2 and the wild type, comprising 4055 up-regulated and 3142 down-regulated genes. GO and KEGG enrichment analyses revealed that down-regulated DEGs were primarily enriched in photosynthesis, plastid function, and related metabolic pathways. Conversely, up-regulated DEGs were enriched in adaptive response pathways, including cell cycle, DNA metabolism, nucleic acid replication, metabolic reprogramming, and damage repair. Western blot analysis showed significantly reduced protein levels of the photosystem Ⅱ core proteins PsbE and PsbO, the photosystem I core protein PsaA, and the light-harvesting complex component LHCa1 in the mutant.ConclusionThe gene responsible for the albino lethal phenotype in the rice wll2 mutant is OsDXS1, a key gene in the MEP pathway. Loss of function of OsDXS1 disrupts chlorophyll biosynthesis and impairs chloroplast development, ultimately leading to the albino lethal phenotype.}
}