Inhibition of Germination Gene Expression by Viviparous-1 and ABA during Maize Kernel Development

Abstract

Two maize glyoxysomal genes expressed during germination, malate synthase (MS) and isocitrate lyase (ICL), were used to characterize the regulatory roles of the Viviparous-1 (Vp1) regulatory gene and abscisic aicd (ABA) in the induction of embryo quiescence during kernel development. In wild-type maize embryo, MS and ICL transcripts were first detected at 2 (MS) or 3 (ICL) days after germination (DAG), peaked at 5 DAG, and decreased thereafter. By reverse transcriptase-polymerase chain reaction (RT-PCR), the germination-specific genes were amplified in both ABA-insensitive (vp1) and ABA-deficient (vp7 and vp10) mutant embryos at 26 and 33 days after pollination (DAP), but not in wild-type embryos. The repression of these germination-specific genes thus requires the Vp1 gene product and normal levels of ABA to induce embryo quiescence during kernel development. This suggests that a genetic regulatory system exists to prevent vivipary in developing maize embryos. The involvement of the Vp1 gene product and ABA in repressing germination-specific genes complements their previously defined roles in the induction of seed-specific genes such as C1.