Variation in patterns of methylations of histone tails reflects and modulates chromatin structure and function1-3. To provide a framework for the analysis of chromatin function in C. elegans, we generated a genome-wide map of histone H3 tail methylations. We find that C. elegans genes show similarities in distributions of histone modifications to those of other organisms, with H3K4me3 near transcription start sites, H3K36me3 in the body of genes, and H3K9me3 enriched on silent genes. Unexpectedly, we also observe a striking novel pattern: exons are preferentially marked with H3K36me3 relative to introns. H3K36me3 exon marking is dependent on transcription and its level is lower in alternatively spliced exons, supporting a splicing related marking mechanism. We further show that the difference in H3K36me3 marking between exons and introns is evolutionarily conserved in human and mouse. We propose that H3K36me3 exon marking in chromatin provides a dynamic link between transcription and splicing.

Highlights d Six high-quality ixodid tick genomes and 678 re-sequenced tick specimens d Insights into the genetic basis of tick hematophagy and related phenotypes d Population structure and genetic diversity of six tick species d Tick-borne pathogen composition and distribution by metagenome analyses

A 3 kb DNA fragment from the Streptomyces globisporus 1912 landomycin E (LaE) biosynthetic gene cluster (lnd) was completely sequenced. Three open reading frames were identified, lndGT4, lndZ4, and lndZ5, whose probable translation products resemble a glycosyltransferase, a reductase, and a hydroxylase, respectively. Studies of generated mutants from disruption and complementation experiments involving the lndGT4 gene allowed us to determine that LndGT4 controls the terminal L-rhodinose sugar attachment during LaE biosynthesis and that LndZ4/LndZ5 are responsible for the unique C11-hydroxylation of the landomycins. Generation of the novel landomycins F, G, and H in the course of these studies provided evidence for the flexibility of lnd glycosyltransferases toward their acceptor substrates and a basis for initial structure-activity relationships within the landomycin family of antibiotics.

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The photoperiodic response is one of the most important factors determining heading date in rice (Oryza sativa). Although rhythmic expression patterns of flowering time genes have been reported to fine-tune the photoperiodic response, posttranslational regulation of key flowering regulators has seldom been elucidated in rice. Heading date 1 (Hd1) encodes a zinc finger transcription factor that plays a crucial role in the photoperiodic response, which determines rice regional adaptability. However, little is known about the molecular mechanisms of Hd1 accumulation during the photoperiod response. Here, we identify a C3HC4 RING domain-containing E3 ubiquitin ligase, Heading date Associated Factor 1 (HAF1), which physically interacts with Hd1. HAF1 mediates ubiquitination and targets Hd1 for degradation via the 26S proteasomedependent pathway. The haf1 mutant exhibits a later flowering heading date under both short-day and long-day conditions. In addition, the haf1 hd1 double mutant headed as late as hd1 plants under short-day conditions but exhibited a heading date similar to haf1 under long-day conditions, thus indicating that HAF1 may determine heading date mainly through Hd1 under short-day conditions. Moreover, high levels of Hd1 accumulate in haf1. Our results suggest that HAF1 is essential to precise modulation of the timing of Hd1 accumulation during the photoperiod response in rice.

Background: Conidia are considered to be the primary cause of infections by Trichophyton rubrum.

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