Integrative Biology

Biography

Biography: Eva Collakova

Abstract

Seed development and metabolism in Arabidopsis are regulated by leafy cotyledon1 (LEC1), Abscisic acid-insensitive3 (ABI3), Fusca3 (FUS3) and LEC2. These transcription factors are part of the core LAFL (LEC1, ABI3, FUS3, and LEC2) regulatory network central to seed development. The action of the LAFL transcription factors is inhibited in germinating seedlings by VAL1 and 2 to suppress the embryonic program during the transition from the embryonic to vegetative state. However, the VALs are also expressed in maturing seed, which appears controversial, considering their role in suppressing the embryonic program. Two VAL1 splice variants were identified through RNA sequencing in developing Arabidopsis embryos: A full-length form containing four domains known to be involved in transcriptional and/or epigenetic regulation and a truncated form lacking the plant-homeodomain-like domain associated with epigenetic repression. Reverse genetics revealed limited influence of the VAL1 absence on seed and embryo metabolomes. However, 3,293 and 2,194 transcripts were up and down-regulated, respectively, in developing val1 mutant embryos relative to the wild type, suggesting that VAL1 is a global regulator of gene expression in developing embryos. Interestingly, none of the transcripts encoding the core LAFL network transcription factors were affected in val1 embryos. Instead, activation of VAL1 by FUS3 appears to result in repression of a subset of seed maturation genes downstream of core LAFL regulators. Transcripts that were not LAFL targets were also de-repressed in developing val1 embryos. Taken together, VAL1 appears to repress its targets through LAFL-dependent and independent mechanisms through epigenetic and/or transcriptional regulation.