Principal investigator: José Luis Micol.
Investigatorss: Carla Navarro-Quiles, Alejandro Ruiz-Bayón, Sergio Navarro-Cartagena, Riad Nadi, Lucía Juan-Vicente, Samuel Daniel Lup-Haruta and Àngela Ortega-Menaches.
Instituto de Bioingeniería. Universidad Miguel Hernández.

Novel plant epigenetic machinery components

In animals, the specification and maintenance of cell fates is controlled (to a large extent) by the epigenetic machinery; indeed, differentiation is thought to be essentially an epigenetic process. Given that few processes seem to be epigenetically regulated in plants, it is tempting to think that epigenetics plays a lesser role in plants. Alternatively, perhaps much remains to be learned about plant epigenetics.

We have discovered a family of five Arabidopsis proteins, which we named CUPULIFORMIS (CP), of the DOXB clade of prolyl 4- hydroxylase domain-containing enzymes. The CP proteins belong to the large 2-oxoglutarate/Fe(II)-dependent dioxygenase superfamily. At least two CP family members, INCURVATA11 (ICU11) and CUPULIFORMIS2 (CP2), are novel components of the epigenetic machinery that act through a mechanism that seems to be unprecedented in eukaryotes. Indeed, emerging data indicate that ICU11 and CP2 act as histone methylases and no other DOXB protein with epigenetic function has been described, and no other 2OGD has been shown to act as a histone methylase.

The icu11 mutants exhibit a mild morphological phenotype, with hyponastic leaves and early flowering. The cp2, cp3, cp4 and cp5 single mutants, as well as all their double and triple cp3 cp4 cp5 mutant combinations are indistinguishable from wild type. By contrast, the icu11 cp2 double mutants are post-embryonic lethal and fail to undergo vegetative development, flowering immediately upon germination, as a consequence of the ectopic and heterochronic derepression of hundreds of genes, which include developmental regulators. Our goal in this project is to provide mechanistic insight into the molecular nature of the epigenetic functions of ICU11 and CP2. Our specific objectives are to identify and characterize (a) the direct or indirect molecular targets of the ICU11-CP2 module, (b) the physical interactors of the ICU11 and CP2 proteins, and (c) the genetic interactors of the ICU11 and CP2 genes. We will also (c) determine the extent of the evolutionary conservation of the epigenetic functions of ICU11 and CP2. A secondary general objective will be to establish if CP3, CP4, and CP5 have any detectable function, and hence deserve study. To this end, we will obtain the icu11 cp3 cp4 cp5 and cp2 cp3 cp4 cp5 quadruple mutants and will characterize their morphological and physiological phenotypes.