White and green striate leaves 1, predicted to encode a 16S rRNA processing protein, plays a critical role in the processing of chloroplast ribosomes in maize (Zea mays L.).

Ribosomes play a crucial role in protein biosynthesis and are linked to plant growth and development. The RimM protein has been shown to be involved in the maturation of 30S ribosomal subunits, but its exact function in plants is still unknown. In this study, we discovered a maize mutant with white and green striate leaves (wgsl1) and reduced chlorophyll content. Genetic analysis showed that the wgsl1 mutation was recessive and controlled by a single nuclear gene. Map-based cloning of ZmWGSL1 identified a base substitution (G to A) that generated a missense mutation within the Zm00001d039036 gene in the wgsl1 mutant. Zm00001d039036 encodes a 16S rRNA processing protein containing the RimM motif. Further analysis of transcriptomic data showed that the transcript levels of many ribosomal proteins involved in the small and big ribosomal subunits were dramatically up-regulated in the wgsl1 mutant. Moreover, the level of ribosomal multimers was decreased. This suggests that ZmWGSL1 plays a crucial role in the maturation of the ribosome, leading to abnormal plant growth and development. In addition, subcellular localization results indicate that WGSL1 is localized in chloroplasts. Therefore, we suggest that WGSL1 is a nuclear-encoded protein, is transported to the chloroplast to drive functions, and affects the processing of ribosomes in the chloroplast. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-023-01407-y.

Genome assembly of the Chinese maize elite inbred line RP125 and its EMS mutant collection provide new resources for maize genetics research and crop improvement.

Maize is an important crop worldwide, as well as a valuable model with vast genetic diversity. Accurate genome and annotation information for a wide range of inbred lines would provide valuable resources for crop improvement and pan-genome characterization. In this study, we generated a high-quality de novo genome assembly (contig N50 of 15.43 Mb) of the Chinese elite inbred line RP125 using Nanopore long-read sequencing and Hi-C scaffolding, which yield highly contiguous, chromosome-length scaffolds. Global comparison of the RP125 genome with those of B73, W22, and Mo17 revealed a large number of structural variations. To create new germplasm for maize research and crop improvement, we carried out an EMS mutagenesis screen on RP125. In total, we obtained 5818 independent M2 families, with 946 mutants showing heritable phenotypes. Taking advantage of the high-quality RP125 genome, we successfully cloned 10 mutants from the EMS library, including the novel kernel mutant qk1 (quekou: "missing a small part" in Chinese), which exhibited partial loss of endosperm and a starch accumulation defect. QK1 encodes a predicted metal tolerance protein, which is specifically required for Fe transport. Increased accumulation of Fe and reactive oxygen species as well as ferroptosis-like cell death were detected in qk1 endosperm. Our study provides the community with a high-quality genome sequence and a large collection of mutant germplasm.