Figure 1.—

A cenh3 null allele in Arabidopsis is embryo lethal. (A) cenh3-1 is predicted to encode a nonfunctional truncated protein. The cenh3-1 gene splices incorrectly, produced a protein that is truncated before the essential histone-fold domain. White boxes, 5′-UTR; dark gray boxes, coding sequence; Light gray boxes, wild-type protein sequence; black box, frameshifted protein sequence resulting from incorrect splicing. (B) Genetic scheme for converting a tetraploid TILLING mutant into a heterozygous diploid. If an allele can be passed from a triploid parent to diploid offspring, it must be transmitted through a haploid gamete. (C) Siliques from wild-type and cenh3-1/CENH3 plants are split open to reveal developing seeds. White seeds indicate embryonic lethality in cenh3-1 homozygous progeny. (D) Genotyping of progeny from cenh3-1/CENH3. The ∼1:2 ratio of CENH3/CENH3 to cenh3-1/CENH3 progeny is consistent with embryonic lethality of cenh3-1. (E) cenh3-1/cenh3-1 embryos arrest at the midglobular stage. Developing seeds in the top and bottom rows were both from cenh3-1/CENH3 siliques. Embryos for each column were fixed at equivalent times after fertilization (labels describe the wild-type developmental stages).