title: The requirement of WHIRLY1 for embryogenesis is dependent on genetic background in maize.
abstract: Plastid gene expression is essential to embryogenesis in higher plants, but the underlying mechanism is obscure. Through molecular characterization of an embryo defective 16 (emb16) locus, here we report that the requirement of plastid translation for embryogenesis is dependent on the genetic background in maize (Zea mays). The emb16 mutation arrests embryogenesis at transition stage and allows the endosperm to develop largely normally. Molecular cloning reveals that Emb16 encodes WHIRLY1 (WHY1), a DNA/RNA binding protein that is required for genome stability and ribosome formation in plastids. Interestingly, the previous why1 mutant alleles (why1-1 and why1-2) do not affect embryogenesis, only conditions albino seedlings. The emb16 allele of why1 mutation is in the W22 genetic background. Crosses between emb16 and why1-1 heterozygotes resulted in both defective embryos and albino seedlings in the F1 progeny. Introgression of the emb16 allele from W22 into A188, B73, Mo17, Oh51a and the why1-1 genetic backgrounds yielded both defective embryos and albino seedlings. Similar results were obtained with two other emb mutants (emb12 and emb14) that are impaired in plastid protein translation process. These results indicate that the requirement of plastid translation for embryogenesis is dependent on genetic backgrounds, implying a mechanism of embryo lethality suppression in maize.
authors.affiliation: Institute of Plant Molecular Biology and Agricultural Biotechnology, State Key Lab of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Shatin, NT, Hong Kong.
authors.forename: Ya-Feng
authors.initials: YF
authors.lastname: Zhang
authors.forename: Ming-Ming
authors.initials: MM
authors.lastname: Hou
authors.forename: Bao-Cai
authors.initials: BC
authors.lastname: Tan
mesh_terms: D002736:Chloroplasts / Q000235:genetics / Q000502:physiology; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005804:Genes, Lethal; D042822:Genomic Instability; D006720:Homozygote; D006824:Hybridization, Genetic; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D036226:Seedlings / Q000166:cytology / Q000235:genetics / Q000502:physiology; D012639:Seeds / Q000166:cytology / Q000235:genetics* / Q000502:physiology; D017384:Sequence Deletion; D003313:Zea mays / Q000166:cytology / Q000235:genetics* / Q000502:physiology
chemical_list: D004268:DNA-Binding Proteins; D010940:Plant Proteins