2 research outputs found
Genome-Wide Transcript Profiling of Endosperm without Paternal Contribution Identifies Parent-of-Origin–Dependent Regulation of AGAMOUS-LIKE36
Seed development in angiosperms is dependent on the interplay among different transcriptional programs operating in the embryo, the endosperm, and the maternally-derived seed coat. In angiosperms, the embryo and the endosperm are products of double fertilization during which the two pollen sperm cells fuse with the egg cell and the central cell of the female gametophyte. In Arabidopsis, analyses of mutants in the cell-cycle regulator CYCLIN DEPENDENT KINASE A;1 (CKDA;1) have revealed the importance of a paternal genome for the effective development of the endosperm and ultimately the seed. Here we have exploited cdka;1 fertilization as a novel tool for the identification of seed regulators and factors involved in parent-of-origin–specific regulation during seed development. We have generated genome-wide transcription profiles of cdka;1 fertilized seeds and identified approximately 600 genes that are downregulated in the absence of a paternal genome. Among those, AGAMOUS-LIKE (AGL) genes encoding Type-I MADS-box transcription factors were significantly overrepresented. Here, AGL36 was chosen for an in-depth study and shown to be imprinted. We demonstrate that AGL36 parent-of-origin–dependent expression is controlled by the activity of METHYLTRANSFERASE1 (MET1) maintenance DNA methyltransferase and DEMETER (DME) DNA glycosylase. Interestingly, our data also show that the active maternal allele of AGL36 is regulated throughout endosperm development by components of the FIS Polycomb Repressive Complex 2 (PRC2), revealing a new type of dual epigenetic regulation in seeds
Water-Soluble Chlorophyll Protein (WSCP) Stably Binds Two or Four Chlorophylls
Water-soluble chlorophyll
proteins (WSCPs) of class IIa from Brassicaceae
form tetrameric complexes containing one chlorophyll (Chl) per apoprotein
but no carotenoids. The complexes are remarkably stable toward dissociation
and protein denaturation even at 100 °C and extreme pH values,
and the Chls are partially protected against photooxidation. There
are several hypotheses that explain the biological role of WSCPs,
one of them proposing that they function as a scavenger of Chls set
free upon plant senescence or pathogen attack. The biochemical properties
of WSCP described in this paper are consistent with the protein acting
as an efficient and flexible Chl scavenger. At limiting Chl concentrations,
the recombinant WSCP apoprotein binds substoichiometric amounts of
Chl (two Chls per tetramer) to form complexes that are as stable toward
thermal dissociation, denaturation, and photodamage as the fully pigmented
ones. If more Chl is added, these two-Chl complexes can bind another
two Chls to reach the fully pigmented state. The protection of WSCP
Chls against photodamage has been attributed to the apoprotein serving
as a diffusion barrier for oxygen, preventing its access to triplet
excited Chls and, thus, the formation of singlet oxygen. By contrast,
the sequential binding of Chls by WSCP suggests a partially open or
at least flexible structure, raising the question of how WSCP photoprotects
its Chls without the help of carotenoids