A LTR retrotransposon insertion leads to leafy phenotype in maize by elevating ZmOM66 expression

Leafy (Lfy1) is a classical dominant mutant showing more leaf number above primary ear and later flowering time in maize, but the causal gene together with its underlying genetic mechanism are unknown. Here, we report the cloning of Lfy1 mutant, and find that a retrotransposon insertion leads to leafy phenotype by elevating expression of its neighboring gene ZmOM66. ZmOM66 encodes an AAA+ ATPase that locate in mitochondria and interacts with itself. ZmOM66 overexpression affects the starch degradation, as well as contents of glucose, pyruvic acid, trehalose-6-phosphate, and TCA cycle related amino acids, and influences expression patterns of circadian clock genes. Moreover, expressions of floral related genes, including photoperiod regulated gene ZmPHYB1, integrator genes ZCN7, ZNC8 and ZCN12, and floral meristem identity genes ZMM4, ZMM15, and MASD67, are also significantly decreased by ZmOM66 overexpression. These results deepen our understanding of the regulatory mechanism of floral transition and leaf number in plant.