Abstract
The rice enl1 mutant bears seeds without endosperm. We mapped the enl1 locus at a region close to the telomere of the Chromosome 4 long arm and identified a deletion of several nucleotides and substitutions in an exon of a predicted gene in this region. Transgenic introduction of a wild type genomic fragment containing this gene completely complemented the mutant phenotype, concluding this gene to be ENL1. ENL1 encodes a protein belonging to the SNF2 class helicase family, which harbors an SNF2 domain and a HELICc domain. Orthologs of ENL1 are conserved among most of eukaryotes. The human ortholog, PICH, is reported to be required for chromosome condensation, chromosome arm architecture, and sister chromatid segregation. Laser confocal microscopic observation of PI-stained syncytial endosperms revealed the presence of giant endosperm nuclei with many nucleoli in the mutant. The abnormality of mutant nuclei appeared to derive from failure in chromosome separation. These results suggest that the errors in the chromosome cycle at the syncytial stage in the enl1 mutant result in the inability of further endosperm development.
