Oryza sativa "Oryza sativa" var. "indica" rice agriculture, before the truly 'wetland' rice "Oryza sativa" var. "japonica", arrived around 2000 BC. Rice was cultivated in the Indus Valley civilization (3rd millennium BC). Agricultural activity during the second millennium BC included rice cultivation in the Kashmir and Harrappan regions. Mixed farming was the basis of Indus valley economy. According to Zohary and Hopf (2000, p. 91), "O. sativa" was recovered from a grave at Susa in Iran (dated to the first century AD) at one end of the ancient world, while at the same time rice was grown in the Po valley 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