A high degree of developmental plasticity enables plants to adapt to continuous, often unfavorable and unpredictable changes in their environment. At the molecular level, adaptive advantages for plants are primarily provided by epigenetic machinery including DNA methylation, histone modifications, and the activity of noncoding RNA molecules. Using a mass spectrometry-based proteomic approach, we examined the levels of acetylated histone peptide forms in Arabidopsis plants with a loss of function of histone deacetylase 6 (HDA6), and in plants germinated in the presence of HDA inhibitors trichostatin A (TSA) and sodium butyrate (NaB). Our analyses revealed particular lysine sites at histone sequences targeted by the HDA6 enzyme, and by TSA- and NaB-sensitive HDAs. Compared with plants exposed to drugs, more dramatic changes in the overall profiles of histone post-translational modifications were identified in hda6 mutants. However, loss of HDA6 was not sufficient by itself to induce hyperacetylation to the maximum degree, implying complementary activities of other HDAs. In contrast to hda6 mutants that did not exhibit any obvious phenotypic defects, the phenotypes of seedlings exposed to HDA inhibitors were markedly affected, showing that the effect of these drugs on early plant development is not limited to the modulation of histone acetylation levels.

• MeSH
• Arabidopsis genetics   growth & development   MeSH
• Histone Deacetylases genetics   MeSH
• Histone Code drug effects   genetics   MeSH
• Histone Deacetylase Inhibitors pharmacology   MeSH
• Germination genetics   MeSH
• Butyric Acid pharmacology   MeSH
• Hydroxamic Acids pharmacology   MeSH
• DNA Methylation drug effects   MeSH
• Arabidopsis Proteins antagonists & inhibitors   genetics   MeSH
• Proteomics * MeSH
• Gene Expression Regulation, Plant MeSH
• Seedlings drug effects   genetics   MeSH
• Gene Silencing MeSH
• Plant Development drug effects   genetics   MeSH
• Publication type
• Journal Article MeSH

MAIN CONCLUSION: Contrasting patterns of histone modifications between the X and Y chromosome in Silene latifolia show euchromatic histone mark depletion on the Y chromosome and indicate hyperactivation of one X chromosome in females. Silene latifolia (white campion) is a dioecious plant with heteromorphic sex chromosomes (24, XX in females and 24, XY in males), and a genetically degenerated Y chromosome that is 1.4 times larger than the X chromosome. Although the two sex chromosomes differ in their DNA content, information about epigenetic histone marks and evidence of their function are scarce. We performed immunolabeling experiments using antibodies specific for active and suppressive histone modifications as well as pericentromere-specific histone modifications. We show that the Y chromosome is partially depleted of histone modifications important for transcriptionally active chromatin, and carries these marks only in the pseudo-autosomal region, but that it is not enriched for suppressive and pericentromere histone marks. We also show that two of the active marks are specifically enriched in one of the X chromosomes in females and in the X chromosome in males. Our data support recent findings that genetic imprinting mediates dosage compensation of sex chromosomes in S. latifolia.

• MeSH
• Chromosomes, Plant genetics   MeSH
• Epigenesis, Genetic * MeSH
• Histone Code genetics   MeSH
• Silene genetics   MeSH
• Publication type
• Journal Article MeSH

Epigenetic mechanisms have not been characterized in ticks despite their importance as vectors of human and animal diseases worldwide. The objective of this study was to characterize the histones and histone modifying enzymes (HMEs) of the tick vector Ixodes scapularis and their role during Anaplasma phagocytophilum infection. We first identified 5 histones and 34 HMEs in I. scapularis in comparison with similar proteins in model organisms. Then, we used transcriptomic and proteomic data to analyze the mRNA and protein levels of I. scapularis histones and HMEs in response to A. phagocytophilum infection of tick tissues and cultured cells. Finally, selected HMEs were functionally characterized by pharmacological studies in cultured tick cells. The results suggest that A. phagocytophilum manipulates tick cell epigenetics to increase I. scapularis p300/CBP, histone deacetylase, and Sirtuin levels, resulting in an inhibition of cell apoptosis that in turn facilitates pathogen infection and multiplication. These results also suggest that a compensatory mechanism might exist by which A. phagocytophilum manipulates tick HMEs to regulate transcription and apoptosis in a tissue-specific manner to facilitate infection, but preserving tick fitness to guarantee survival of both pathogens and ticks. Our study also indicates that the pathogen manipulates arthropod and vertebrate cell epigenetics in similar ways to inhibit the host response to infection. Epigenetic regulation of tick biological processes is an essential element of the infection by A. phagocytophilum and the study of the mechanisms and principal actors involved is likely to provide clues for the development of anti-tick drugs and vaccines.

• MeSH
• Anaplasma phagocytophilum genetics   MeSH
• Apoptosis genetics   MeSH
• Cell Line MeSH
• Epigenesis, Genetic * MeSH
• Histone Code genetics   MeSH
• Histones genetics   metabolism   MeSH
• Insect Vectors genetics   MeSH
• Host-Pathogen Interactions genetics   MeSH
• Ixodes genetics   MeSH
• Humans MeSH
• RNA, Messenger biosynthesis   genetics   MeSH
• p300-CBP Transcription Factors biosynthesis   genetics   MeSH
• Transcriptome genetics   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH