The heterochronic maize mutant Corngrass1 results from overexpression of a tandem microRNA.
Retention of juvenile traits in the adult reproductive phase characterizes a process known as neoteny, and speculation exists over whether it has contributed to the evolution of new species. The dominant Corngrass1 (Cg1) mutant of maize is a neotenic mutation that results in phenotypes that may be present in the grass-like ancestors of maize. We cloned Cg1 and found that it encodes two tandem miR156 genes that are overexpressed in the meristem and lateral organs. Furthermore, a target of Cg1 is teosinte glume architecture1 (tga1), a gene known to have had a role in the domestication of maize from teosinte. Cg1 mutant plants overexpressing miR156 have lower levels of mir172, a microRNA that targets genes controlling juvenile development. By altering the relative levels of both microRNAs, it is possible to either prolong or shorten juvenile development in maize, thus providing a mechanism for how species-level heterochronic changes can occur in nature.
Chuck
George
G
Plant Gene Expression Center, 800 Buchanan St., Albany, California 94710, USA. gchuck@nature.berkeley.edu
Cigan
A Mark
AM
Saeteurn
Koy
K
Hake
Sarah
S
D001483:Base Sequence; D003001:Cloning, Molecular; D019143:Evolution, Molecular; D035683:MicroRNAs / Q000235:genetics*; D008969:Molecular Sequence Data; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics*; D030821:Plants, Genetically Modified; D012091:Repetitive Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid; D003313:Zea mays / Q000235:genetics*
D035683:MicroRNAs; D010940:Plant Proteins