The Discovery of LABA1, a Gene Associated with Long, Barbed Awns in Wild Rice

Common wild rice (Oryza rufipogon), the wild relative of Oryza sativa, has long and barbed awns. By contrast, O. sativa cultivars have been selected to be awnless for ease of seed processing and storage. The transition from long, barbed awns to short, barbless awns was a crucial event in rice domestication.

A team composed of researchers from the China Agricultural University and the Hunan Agricultural University of China and Cornell University in the U.S., recently found that the presence of long, barbed awns in wild rice is controlled by a major gene on chromosome 4, the LONG AND BARBED AWN1 (LABA1), which encodes a cytokinin-activating enzyme. The increase in cytokinin concentration promoted the growth of barbs and the elongation of awns.

On the other hand, the laba1 allele of cultivated rice, which contains a frame-shift deletion, reduced the cytokinin concentration in the awn primordia, disrupting barb formation and awn elongation. Further analysis revealed that the laba1 allele originated in the japonica subspecies and moved into the indica gene pool via introgression, suggesting that humans selected for this trait in early rice domestication.

Identification of LABA1 provides new insights into rice domestication and also sheds light on the mechanism of awn development.

For more information on this study, read the full article on The Plant Cell.