The Histone Deacetylase Complex (HDC) 1 protein of Arabidopsis thaliana has the capacity to interact with multiple proteins including histone 3-binding proteins and histone 1 variants

Intrinsically disordered proteins can adopt multiple conformations thereby enabling interaction with a wide variety of partners. They often serve as hubs in protein interaction networks. We have previously shown that the Histone Deacetylase Complex (HDC) 1 protein from Arabidopsis thaliana interacts with histone deacetylases and quantitatively determines histone acetylation levels, transcriptional activity and several phenotypes, including ABA-sensitivity during germination, vegetative growth rate and flowering time. HDC1-type proteins are ubiquitous in plants but they contain no known structural or functional domains. Here we explored the protein interaction spectrum of HDC1. In addition to binding histone deacetylases, HDC1 directly interacted with core histone H3-binding proteins and co-repressor associated proteins, but not with H3 or the co-repressors themselves. Surprisingly, HDC1 was also able to interact with variants of the linker histone H1. Truncation of HDC1 to the ancestral core sequence narrowed the spectrum of interactions and of phenotypic outputs but maintained binding to a H3-binding protein and to H1. The results indicate a potential link between H1 and histone modifying complexes

Abiotikus stressztényezők hatása a kukorica (Zea mays L.) anyagcseréjére és egyedfejlődésére = Effect of abiotic stress factors on maize (Zea mays L.) metabolism and plant development

Kutatásunk során a kénanyagcsere egyik meghatározó intermedierjének, az S-metil-metioninnak (SMM) alacsony hőmérsékleti stresszt csökkentő hatását tanulmányoztuk elsősorban kukoricában. Bizonyítottuk az SMM-indukált poliaminszintézis tényét nemcsak kukoricában, hanem más gazdasági növényekben is. Megállapítottuk, hogy a hidegre érzékeny beltenyésztett kukoricavonalakban nagyobb mennyiségben szintetetizálódik SMM hatására spermidin, mint a toleráns genotípusokban. Az SMM-indukált spermidin nemcsak a kukoricában, hanem más gazdasági növényekben (őszi búza, borsó, szója) is csökkenti a membránok károsodását, és ezen keresztül az ionkiáramlás mértékét. Igazoltuk az SMM fotoszintézisre gyakorolt pozitív hatását is, mert megnöveli a PSII hatékonyságát jellemző Fv/Fm hányadost, és megemeli az össz-klorofill mennyiségét a kukorica genotípusok leveleiben szuboptimális (6-10°C) hőmérsékleteken. Bizonyítottuk, hogy alacsony hőmérsékleti stressz során az SMM egyes antioxidáns enzimek aktivitását serkenti, így csökkentve közvetve a reaktív oxigénformák káros hatását. Részletesen tanulmányoztuk a poliaminszintézis kulcsenzimeinek (ADC, ODC, SAMDC) génexpresszióját 24 órás SMM, illetve SMM+hidegkezelés hatására. Megállapítottuk, hogy a legnagyobb változás az ADC expressziójában volt kimutatható. Igazoltuk, hogy mind a hideg, mind az SMM hatására már az első órától kezdve gyorsan emelkedett a CBF faktor expressziója is. | Investigations were made on the ability of S-methyl-methionine (SMM), an important intermediary compound in the sulphur metabolism, to reduce low temperature stress, especially in maize. The existence of SMM-induced polyamine synthesis was confirmed not only in maize, but also in other crops. It was found that larger quantities of spermidine were synthesised in response to SMM treatment in chilling-sensitive inbred maize lines than in tolerant genotypes. The SMM-induced spermidine reduced membrane damage, and consequently the extent of electrolyte leakage, not only in maize, but also in other crops (winter wheat, pea, soybeans). SMM was also demonstrated to have a positive effect on photosynthesis, since it increased the Fv/Fm quotient indicative of the efficiency of PSII and induced a rise in the total chlorophyll content in the leaves of maize genotypes at suboptimal (6?10°C) temperatures. In the course of low temperature stress SMM was shown to stimulate the activity of certain antioxidant enzymes, thus indirectly reducing the damaging effect of reactive oxygen species. Detailed studies were made on the gene expression of key enzymes in polyamine synthesis (ADC, ODC, SAMDC) as the result of 24-h treatment with SMM or SMM + chilling. The greatest change was detected in the ADC expression. Both chilling and SMM led to a rapid increase in the expression of the CBF factor within an hour of treatment.

Repression of chromomethylase 3 prevents epigenetic collateral damage in arabidopsis

DNA methylation has evolved to silence mutagenic transposable elements (TEs) while typically avoiding the targeting of endogenous genes. Mechanisms that prevent DNA methyltransferases from ectopically methylating genes are expected to be of prime importance during periods of dynamic cell cycle activities including plant embryogenesis. However, virtually nothing is known regarding how DNA methyltransferase activities are precisely regulated during embryogenesis to prevent the induction of potentially deleterious and mitotically stable genic epimutations. Here, we report that microRNA-mediated repression of CHROMOMETHYLASE 3 (CMT3) and the chromatin features that CMT3 prefers help prevent ectopic methylation of thousands of genes during embryogenesis that can persist for weeks afterwards. Our results are also consistent with CMT3-induced ectopic methylation of promoters or bodies of genes undergoing transcriptional activation reducing their expression. Therefore, the repression of CMT3 prevents epigenetic collateral damage on endogenous genes. We also provide a model that may help reconcile conflicting viewpoints regarding the functions of gene-body methylation that occurs in nearly all flowering plants