CHROMOMETHYLTRANSFERASE3/KRYPTONITE maintains the sulfurea paramutation in Solanum lycopersicum

Paramutation involves the transfer of a repressive epigenetic mark from a silent allele to an active homolog and, consequently, non-Mendelian inheritance. In tomato, the sulfurea (sulf) paramutation is associated with a high level of CHG hypermethylation in a region overlapping with the transcription start site (TSS) of the SlTAB2 gene that affects chlorophyll synthesis. The CCG subcontext hypermethylation is under-represented at this region relative to CTG or CAG, implicating the CHROMOMETHYLTRANSFERASE3a (CMT3) in paramutation at this locus. Consistent with this interpretation, loss of CMT3 function leads to loss of the sulf chlorosis, the associated CHG hypermethylation, and paramutation. Loss of KRYPTONITE (KYP) histone methyltransferase function has a similar effect linked to reduced H3K9me2 at the promoter region of SlTAB2 and a shift in higher order chromatin structure at this locus. Mutation of the largest subunit of RNA polymerase V (PolV) in contrast does not affect sulf paramutation. These findings indicate the involvement of a CMT3/KYP–dependent feedback loop rather than the PolV-dependent pathway leading to RNA-directed DNA methylation (RdDM) in the maintenance of paramutation

CHROMOMETHYLTRANSFERASE3/ KRYPTONITE maintain the sulfurea paramutation in Solanum lycopersicum

Paramutation involves the transfer of a repressive epigenetic mark from a silent allele to an active homologue and, consequently, non-Mendelian inheritance. In tomato the sulfurea (sulf) paramutation is associated with a high level of CHG hypermethylation in a region overlapping the transcription start site of the SlTAB2 gene that affects chlorophyll synthesis. The CCG sub-context hypermethylation is under-represented at this region relative to CTG or CAG implicating the CHROMOMETHYLTRANSFERASE3 (CMT3) in paramutation at this locus. Consistent with this interpretation, loss of CMT3 function leads to loss of the sulf chlorosis, the associated CHG hypermethylation and paramutation. Loss of KRYPTONITE (KYP) histone methyl transferase function has a similar effect linked to reduced H3K9me2 at the promoter region of SlTAB2 and a shift in higher order chromatin structure at this locus. Mutation of the largest subunit of RNA polymerase V (PolV) in contrast does not affect sulf paramutation. These findings indicate the involvement of a CMT3/KYP dependent feedback rather than the PolV-dependent pathway leading to RNA directed DNA methylation (RdDM) in the maintenance of paramutation

Studio e analisi di Markarian 421 e 0235+164

Lo scopo di questa tesi è l’analisi del flusso dei nuclei e dei getti di due sorgenti quasar: Markarian 421 e 0235+164. Il lavoro si concentra nella prima parte sull’esposizione di concetti astrofisici noti (come AGN e modello unificato) e una breve descrizione degli interferometri utilizzati per l’acquisizione dati. Lo studio si basa su immagini e dati recuperati sul sito Blazar Group della Boston University che monitora mensilmente i getti radio di numerose sorgenti tramite il radiotelescopio VLBA. Questi dati sono stati sfruttati per determinare l’andamento nel tempo del picco e dell’integrale del flusso del nucleo e dei getti, riportando tali valori su grafici

The regulation of ascorbic acid biosynthesis by blue light receptors in Arabidopsis thaliana

Ascorbic acid, or vitamin C, is one of the most abundant molecules in plant cells and plays an essential role in multiple processes, including ROS scavenging, cell signalling and enzyme catalysis. Here, we aimed at identifying and characterizing the genes which are involved in the regulation of ascorbic acid levels in Arabidopsis thaliana. For this purpose, ascorbic acid concentration in the leaves of 300 different accessions of A. thaliana was measured by HPLC and a genome-wide association study (GWAS) was performed. Some of the most statistically significant polymorphisms were located in the gene sequence of PAS/LOV protein (PLP), which encodes a putative blue light receptor. Two isoforms, namely PLPA and PLPB, were previously demonstrated to interact in vitro with VITAMIN C DEFECTIVE 2 (VTC2), a critical enzyme involved in ascorbic acid biosynthesis. To assess whether the interaction occurs also in vivo, a Bimolecular Fluorescence Complementation (BiFC) assay was performed, which allowed to detect a strong interaction of PLPA and PLPB with VTC2. The interaction occurs in globular bodies located in the cytoplasm, which were ruled out to be mitochondria and are speculated to be peroxisomes, stress granules or cytoplasmic photobodies. Moreover, our observations indicate that blue light strengthens the interaction between PLPA and VTC2. To further investigate the role of blue light in the regulation of ascorbic acid levels, the concentration of vitamin C in leaves of A. thaliana treated either with white light or blue light were compared. In addition to the wild-type genotype, several mutants were grown, including knock-out lines of well-known photoreceptors like phototropins and cryptochromes. The results showed that vitamin C is significantly higher in the blue light treated plants for all the genotypes, excluding the cryptochrome1/cryptochrome2 double mutant, for which there was no difference between the light treatments. This suggests that cryptochromes are responsible for the blue light-induced increase in ascorbic acid. Cryptochromes have a prominent role in the inhibition of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), an E3 ubiquitin ligase that acts as a master regulator of protein degradation in the dark. Because the primary structures of both PLPB and VTC2 have a COP1 recognition motif, we decided to test their interaction with COP1 by a yeast-two-hybrid assay, which turned out to be positive in both cases. In conclusion, our experiments indicate that blue light strongly influences ascorbic acid levels in A. thaliana. We collected evidence suggesting an important role of blue light receptors like PLP and cryptochromes in vitamin C biosynthesis and proposed possible molecular mechanisms through which they may act

Carta Geografica Dello Stato Della Chiesa Granducato Di Toscana E De' Stati Adjacenti

CARTA GEOGRAFICA DELLO STATO DELLA CHIESA GRANDUCATO DI TOSCANA E DE' STATI ADJACENTI Carta Geografica Dello Stato Della Chiesa Granducato Di Toscana E De' Stati Adjacenti ( -

Stable bundles and the first eigenvalue of the Laplacian

In this article we study the first eigenvalue of the Laplacian on a compact manifold using stable bundles and balanced bases. Our main result is the following: Let M be a compact Kahler manifold of complex dimension n and E a holomorphic vector bundle of rank r over M. If E is globally generated and its Gieseker point T-E is stable, then for any Kahler metric g on

CHROMOMETHYLTRANSFERASE3/KRYPTONITE maintains the sulfurea paramutation in Solanum lycopersicum.

SignificanceParamutation involves the transfer of a repressive epigenetic mark between silent and active alleles. It is best known from exceptional non-Mendelian inheritance of conspicuous phenotypes in maize but also in other plants and animals. Recent genomic studies, however, indicate that paramutation may be less exceptional. It may be a consequence of wide-cross hybridization and may contribute to quantitative trait variation or unstable phenotypes in crops. Using the sulfurea (sulf) locus in tomato, we demonstrate that a self-reinforcing feedback loop involving DNA- and histone-methyl transferases CHROMOMETHYLTRANSFERASE3 (CMT3) and KRYPTONITE (KYP) is required for paramutation of sulf and that there is a change in chromatin organization. These findings advance the understanding of non-Mendelian inheritance in plants.This study was supported by the BBSRC grant PDAG/387 RG8739