Perennial rice for distribution. Domesticated Asian rice, "Oryza sativa" is a short-lived plant. Most cultivars die after producing seeds, though some can regrow (ratoon) and produce a second crop under favorable conditions. In regions with mild climates, two or three crops of rice may be grown each year. Except for ratoon crops, this means that the dead stalks must be removed, the soil cultivated, and new seed sown every few months. In contrast, the wild ancestor of Asian rice, "Oryza rufipogon", often lives for many years, setting seed each year and spreading vegetatively. In addition to these perennial types, some "O. rufipogon"
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