Oryza sativa estimated to be 8,200 to 13,500 years ago. This is consistent with known archaeological data on the subject. An older theory, based on one chloroplast and two nuclear gene regions, Londo "et al." (2006) had proposed that "O. sativa" rice was domesticated at least twice—"indica" in eastern India, Myanmar, and Thailand; and "japonica" in southern China and Vietnam—though they concede that archaeological and genetic evidence exist for a single domestication of rice in the lowlands of China. Because the functional allele for nonshattering, the critical indicator of domestication in grains, as well as five other single-nucleotide polymorphisms, is identical in
Helitron (biology) Helitron (biology) Helitrons are one of the three groups of eukaryotic class 2 transposable elements (TEs) so far described. They are the eukaryotic rolling-circle transposable elements which are hypothesized to transpose by a rolling circle replication mechanism via a single-stranded DNA intermediate. They were first discovered in plants ("Arabidopsis thaliana" and "Oryza sativa") and in the nematode "Caenorhabditis elegans", and now they have been identified in a diverse range of species, from protists to mammals. Helitrons make up a substantial fraction of many genomes where non-autonomous elements frequently outnumber the putative autonomous partner. Helitrons seem to have a major role