Integrated control of seed maturation and germination programs by activator and repressor functions of Viviparous-1 of maize.

Abstract

The Viviparous-1 (VP1) transcriptional activator of maize is required for abscisic acid induction of maturation-specific genes late in seed development leading to acquisition of desiccation tolerance and arrest in embryo growth. Here, we show that VP1 also inhibits induction of the germination-specific a-amylase genes in aleurone cells of the developing seed and thereby appears to be involved in preventing precocious hydrolyzation of storage compounds accumulating in the endosperm. In developing seeds of the somatically instable vpl-m2 mutant, hydrolase activity was derepressed specifically in endosperm sectors underlying vpl mutant aleurone. A barley a-amylase promoter-GUS reporter construct (Amy-GUS) was induced in developing vpl mutant aleurone cells but not in wild-type aleurone cells. Moreover, transient expression of recombinant VP1 in vpl mutant aleurone cells strongly inhibited expression of Amy-GUS and thus effectively complemented this aspect of the mutant phenotype. VP1 specifically repressed induction of Amy-GUS by the hormone gibberellic acid in aleurone of germinating barley seeds. Deletion of the acidic transcriptional activation domain of VP1 did not affect the inhibitory activity, indicating that VP1 has a discrete repressor function. Hence, physically combining activator and repressor functions in one protein may provide a mechanism to integrate the control of two normally consecutive developmental programs, seed maturation and seed germination.

anthocyanin1 of Petunia Encodes a Basic Helix-Loop-Helix Protein That Directly Activates Transcription of Structural Anthocyanin Genes

“…In maize, transcription of c1 is controlled by VIVIPAROUS1 (VP1), a transcriptional regulator that controls multiple aspects of seed maturation, including anthocyanin synthesis, seed dormancy, and expression of amylase genes (Hoecker et al, 1995;Suzuki et al, 1997). Our data on an1 indicate that the anthocyanin-specific regulators also operate in some sort of transcriptional hierarchy.…”

The Transcription Factors HvABI5 and HvVP1 Are Required for the Abscisic Acid Induction of Gene Expression in Barley Aleurone Cells

“…VP1 has been described to play dual roles as a positive regulator of the ABA induction of maturationspecific genes in late seed development and as a repressor of the induction of germination-specific ␣-amylase genes (Hoecker et al, 1995). If VP1 has inhibitory activity on the GA induction of ␣-amylase in seeds, we would expect an increase of GUS activity when the HvVP1-RNAi construct is used.…”

Transcriptome dynamics of developing maize leaves and genomewide prediction ofciselements and their cognate transcription factors

“…B3 proteins interact with auxin or ABA signaling pathways to regulate embryogenesis and the development of shoot meristem or leaf shape (48,49). The most highly expressed B3 gene, coding for VP1, regulates seed maturation and germination (50). MYB proteins are involved in primary and secondary metabolism, cell fate and identity, developmental processes, and biotic and abiotic stress responses (51).…”