Abstract
Abscisic acid (ABA) is required as a co-regulatory factor for all of the regulatory functions associated with Viviparous-1 (Vp1) during maize kernel development. The exception has been anthocyanin synthesis, because carotenoid-deficient viviparous mutants have reduced endogenous ABA but still accumulate anthocyanin pigments. However, if full color kernel blocks are cultured on fluridone medium to reduce endogenous ABA to near zero levels, anthocyanin synthesis is repressed. Addition of exogenous ABA to fluridone medium induces anthocyanin synthesis. Vp1 is expressed in the presence or absence of ABA, but C1 is expressed only when ABA is present. The content of C1 transcripts is increased by adding exogenous ABA into standard medium. When all dominant genes for anthocyanin expression in aleurone tissue are present, the timing and intensity of anthocyanin expression depend on ABA concentration. Both maternal and exogenous ABA are transported into developing maize kernels, and the source of ABA is irrelevant. Genes coding for maize lipase (LIP) and malate synthase (MS) enzymes involved in lipolysis and glyoxylate cycle during germination were cloned to elucidate the Vp1 and ABA regulatory role for the induction of embryo quiescence. The MS and LIP genes are expressed in ABA-insensitive (vp1) and ABA-deficient (vp7, vp10) mutants but not in wild-type embryos at 26 days after pollination (DAP). It appears that Vp1 and ABA regulation is involved in the repression of germination genes at the transcriptional level. This suggests that two major regulatory systems exist for preventing vivipary. The one set of germination genes is down-regulated by ABA alone and the other is by Vp1 and ABA to induce embryo quiescence during maize kernel development. The Vp1 transcription activator regulates the target genes in specific tissue types and then the level of expression is controlled by the concentration of ABA in developing maize kernels.
Paek, Nam Chon (1994). Regulation of anthocyanin synthesis and embryo quiescence by Viviparous-1 and abscistic acid during maize kernel development. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -1554652.