Root or shoot? EAR calls the shots

The lens shaped cell (shown in green) at the base of the plant embryo (shown in red) will go on to form the center of the root meristem -- the actively dividing cell tissue at the tips of roots. It fluoresces green in response to auxin, which governs root development (far left). Embryos with a mutation in the TOPLESS gene still respond normally to auxin (second from left), while embryos without a functional version of BODENLOS cannot respond to auxin and as a result fail to develop roots (second from right). Combining both mutations restores the auxin response as well as root development (far right). Courtesy of Dr. Jeffrey Long, Salk Institute for Biological Studies