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

Two maize glyoxysomal genes expressed during germination, malate synthase (MS) and isocitrate lyase (ICL), were used to characterize the regulatory roles of the Viviparous-l (Vpl) 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 transcriptasepolymerase chain reaction (RT-PCR), the germinationspecific genes were amplified in both ABA-insensitive (vpl) and ABA-deficient (vp7 and vplO) mutant embryos at 26 and 33 days after pollination (DAP), but not in wild-type embryos. The repression of these germination-specific genes thus r equires the Vpl 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 Vpl gene product and ABA in repressing germination-specific genes complements their previously defined roles in the induction of seed-specific genes such as Cl (Hattori et al., 1992; Paek et aI. , 1997), Em (McCarty et aI., 1991), and Glnl (Kriz et aI., 1990; Rivin and Grudt, 1991). [ABSTRACT FROM AUTHOR]