Biology subjects

Gomez-Zambrano, A.

Publications and source records attributed to Gomez-Zambrano, A..

3 recordsLinked to original sources

bioRxiv2020

Fibrillin 2 interacts with other proteins to protect photosystem II against abiotic stress in Arabidopsis

Fibrillins (FBNs) are plastidial proteins found in photosynthetic organisms, from cyanobacteria to higher plants. The function of most FBNs is largely unknown. We focused on the subgroup formed by FBN1a, -1b, and -;2, which has been proposed to be involved in the photoprotection of photosystem II (PSII), though their mechanism of action has not yet been characterized. We show that FBN2 interacts with FBN1a and with other FBN2 polypeptides, potentially forming a network around the plastoglobule surface. Both FBN2 and FBN1 interact with the allene oxide synthase, and the elimination of any of these FBNs results in a delay in jasmonate-mediated anthocyanin accumulation in response to a combination of moderate-high light and low temperature. FBN2 also interacts with other proteins involved in different metabolic processes. Mutants lacking FBN2 demonstrate less photoprotection of PSII, alterations that are not found in fbn1a-fbn1b mutants. We also show that FBN2 interacts with Acclimation of Photosynthesis to Environment 1 (APE1), and gene co-expression analysis suggests that both proteins are involved in the same metabolic process. The elimination of APE1 leads to lesions in PSII under abiotic stress similar to observations in fbn2 mutants, with lower maximum and effective quantum yield. However, a reduction in non-photochemical quenching is observed exclusively in fbn2 mutants, suggesting that other FBN2-interacting proteins are responsible for this alteration. We propose that FBN2 facilitates accurate positioning of different proteins involved in distinct metabolic processes, and its elimination leads to dysfunction in those proteins. One sentence summaryFibrillin 2 protects photosynthesis against abiotic stresses by facilitating the accurate positioning of different proteins involved in distinct processes, and its elimination leads to dysfunction in those proteins

plant biology↗

bioRxiv2020

DNA polymerase epsilon is a central coordinator of heterochromatin structure and function in Arabidopsis

BackgroundChromatin organizes the DNA molecule and regulates its transcriptional activity through epigenetic modifications. Heterochromatic regions of the genome are generally transcriptionally silent while euchromatin is more prone to transcription. During DNA replication, both genetic information and chromatin modifications must be faithfully passed on to daughter strands. There is evidence that DNA polymerases play a role in transcriptional silencing, but the extent of their contribution and how it relates to heterochromatin maintenance is unclear. ResultsWe isolate a strong hypomorphic Arabidopsis thaliana mutant of the POL2A catalytic subunit of DNA polymerase epsilon and show that POL2A is required to stabilize heterochromatin silencing genome wide, likely by preventing replicative stress. We reveal that POL2A inhibits DNA methylation and histone H3 lysine 9 methylation. Hence, release of heterochromatin silencing in POL2A deficient mutants paradoxically occurs in a chromatin context of increased level of these two repressive epigenetic marks. At the nuclear level, POL2A defect is associated with fragmentation of heterochromatin. ConclusionThese results indicate that POL2A is critical to secure both heterochromatin structure and function. We also reveal that unhindered replisome progression is required for the faithful propagation of DNA methylation through the cell cycle.

genomics↗

bioRxiv2018

Differential requirement of MED14 and UVH6 for heterochromatin transcription upon destabilization of silencing

Constitutive heterochromatin is commonly associated with high levels of repressive epigenetic marks and is stably maintained transcriptionally silent by the concerted action of different, yet convergent, silencing pathways. Reactivation of heterochromatin transcription is generally associated with alterations in levels of these epigenetic marks. However, in mutants for particular epigenetic regulators, or upon particular environmental changes such as heat stress, heterochromatin-associated silencing is destabilized without noticeable changes in epigenetic marks. This suggests that transcription can occur in a non-permissive chromatin context, yet the factors involved remain poorly known. Here, we show that heat stress-induced transcription of heterochromatin depends on the TFIIH component UVH6 and the Mediator subunit MED14. Mutants for these two factors exhibit hypersensitivity to heat stress, and under these conditions, UVH6 and MED14 are required for transcription of a high number of loci. We further show that MED14, but not UVH6, is required for transcription when heterochromatin silencing is destabilized in the absence of stress. In this case, MED14 requires proper chromatin patterns of repressive epigenetic marks for its function. We also uncover that MED14 regulates non-CG DNA methylation at a subset of RNA-directed DNA methylation target loci. These findings provide insight into the control of heterochromatin transcription upon silencing destabilization and identify MED14 as a regulator of DNA methylation.

plant biology↗