No abstract

Efforts to elucidate the contributions by transcription factors to plant gene expression will require increasing knowledge of their specific in vivo regulatory associations. We are systematically investigating the role of individual TGA factors in the transcriptional control of pathogenesis-related (PR) defense genes, whose expression is stimulated in leaves by salicylic acid (SA) through a stimulus pathway involving NPR1. We focused on PR-1 because its SA-induced expression in Arabidopsis is mediated by an as-1 -type promoter cis element ( LS7 ) that is recognized in vitro by TGA factors. We found that two NPR1-interacting TGA factors, TGA2 and TGA3, are the principal contributors to an LS7 binding activity of leaves that is enhanced by SA through NPR1. The relevance of these findings to PR-1 expression was investigated by the use of chromatin immunoprecipitation, which demonstrated that in vivo these TGA factors are strongly recruited in an SA-and NPR1-dependent manner to the LS7 -containing PR-1 promoter. Significantly, the timing of promoter occupancy by these factors is linked to the SA-induced onset and sustained expression of PR-1 . Because leaf transfection assays indicate that TGA3 activates transcription, as noted previously for TGA2, these two TGA factors are predicted to make positive contributions to the expression of this target gene. Thus, the findings presented here distinguish among different modes of regulation by these transcription factors and provide strong support for their direct role in the stimulus-activated expression of an endogenous defense gene.

Most reported cases of human monkeypox occur in Central and West Africa, where the causing virus is endemic. We describe the identification and public health response to an imported case of West African monkeypox from Nigeria to the United Kingdom (UK) in May 2021. Secondary transmission from the index case occurred within the family to another adult and a toddler. Concurrent COVID-19-related control measures upon arrival and at the hospital, facilitated detection and limited the number of potential contacts.

SummaryWe have developed two long-oligonucleotide microarrays for the analysis of genome features in Arabidopsis thaliana, in particular for the high-throughput identification of transcription factor-binding sites. The first platform contains 190 000 probes representing the 2-kb regions upstream of all annotated genes at a density of seven probes per promoter. The second platform is divided into three chips, each of over 390 000 features, and represents the entire Arabidopsis genome at a density of one probe per 90 bases. Protein-DNA complexes resulting from the formaldehyde fixation of leaves of plants 2 h after exposure to 1 mM salicylic acid (SA) were immunoprecipitated using antibodies against the TGA2 transcription factor. After reversal of the cross-links and amplification, the resulting ChIP sample was hybridized to both platforms. High signal ratios of the ChIP sample versus raw chromatin for clusters of neighboring probes provided evidence for 51 putative binding sites for TGA2, including the only previously confirmed site in the promoter of PR-1 (At2g14610). Enrichment of several regions was confirmed by quantitative real-time PCR. Motif search revealed that the palindromic octamer TGACGTCA was found in 55% of the enriched regions. Interestingly, 15 of the putative binding sites for TGA2 lie outside the presumptive promoter regions. The effect of the 2-h SA treatment on gene expression was measured using Affymetrix ATH1 arrays, and SA-induced genes were found to be significantly over-represented among genes neighboring putative TGA2-binding sites.

Neurospora crassa, Aspergillus nidulans, and other ascomycetous fungi are able to utilize a wide array of nitrogen sources, and many of the pathways involved are regulated at the level of transcription by pathway-specific control proteins. When the preferred nitrogen sources ammonium or glutamine are present in the growth medium with an alternative nitrogen source, the pathway for the non-preferred source remains inactive. This situation is known as nitrogen metabolite repression, and the alternate nitrogen utilization pathway is said to be repressed (1). These observations show there is a signal transduction pathway that responds to the presence of ammonium/ glutamine and targets the control of transcription of the genes involved in nitrogen metabolism.

The Salmonella typhimurium "yeaZ" gene (StyeaZ) encodes an essential protein of unknown function (StYeaZ), which has previously been annotated as a putative homolog of the Pasteurella haemolytica M22 O-sialoglycoprotein endopeptidase Gcp. YeaZ has also recently been reported as the first example of an RPF from a gram-negative bacterial species. To further characterize the properties of StYeaZ and the widely occurring MK-M22 family, we describe the purification, biochemical analysis, crystallization, and structure determination of StYeaZ. The crystal structure of StYeaZ reveals a classic two-lobed actin-like fold with structural features consistent with nucleotide binding. However, microcalorimetry experiments indicated that StYeaZ neither binds polyphosphates nor a wide range of nucleotides. Additionally, biochemical assays show that YeaZ is not an active O-sialoglycoprotein endopeptidase, consistent with the lack of the critical zinc binding motif. We present a detailed comparison of YeaZ with available structural homologs, the first reported structural analysis of an MK-M22 family member. The analysis indicates that StYeaZ has an unusual orientation of the A and B lobes which may require substantial relative movement or interaction with a partner protein in order to bind ligands. Comparison of the fold of YeaZ with that of a known RPF domain from a gram-positive species shows significant structural differences and therefore potentially distinctive RPF mechanisms for these two bacterial classes.

Precocious maturation of artificially propagated male Chinook salmon Oncorhynchus tshawytscha has the potential to alter abundance and distribution of males in freshwater and thereby influence ecological and genetic interactions with other fish in the natural environment. Between 1999 and 2007, the Cle Elum Supplementation and Research Facility has produced and released into the upper Yakima River basin of Washington an annual average of 124,573 males that mature precociously. We investigated the abundance and distribution of precociously mature male spring Chinook salmon of hatchery and natural (wild) origin during the spawning season (4–7 months after hatchery release) in the Yakima River. We counted the number of precocious males on the spawning grounds while snorkeling during the peak of spawning and electrofished to determine abundance and distribution of precocious males away from redds. We also collected Chinook salmon to determine percent precocity and size and age distributions. The number of precocious hatchery males on redds was less than 0.05% of the total number of fish released, and they were significantly less abundant on redds than precocious wild males. Between 1999 and 2007, the mean annual abundance of precocious age‐1 hatchery males observed on the spawning grounds was 22 fish (range, 0–78). Precocious hatchery and wild males were both found throughout the spawning range during the spawning season, but significant differences in distribution between origins were detected. Precocious hatchery males were proportionately more abundant in the most downstream sampling reach and less abundant in a tributary with no hatchery facilities. In addition, most precocious hatchery males were found downstream of spawning areas during the spawning season. It appears that many precocious hatchery males migrate downstream from release and fail to migrate back to the spawning grounds, or they die within the Yakima River before spawning. Thus, precocious male Chinook salmon resulting from hatchery production in the Yakima River do not contribute favorably to harvest and may pose ecological risks to other taxa, but most of these fish have a low probability of contributing genes to future generations.

SummaryXenobiotic chemicals induce the expression of nuclear detoxi®cation genes. A full understanding of this protective response will require characterization of its transcriptional regulatory machinery. We describe here the use of a recently developed plant chromatin immunoprecipitation (ChIP) assay to de®ne nuclear promoter targets of TGA1a, a tobacco basic/leucine zipper transcription factor whose activity is potentiated by herbicide-induced xenobiotic stress. TGA1a selectively binds as-1-type cis-elements, which regulate transcription of putative detoxi®cation and defense genes. With ChIP, we show that endogenous TGA1a binds as-1-containing promoter sequences of two tobacco glutathione S-transferase genes, GNT1 and GNT35. This binding activity is strongly enhanced by xenobiotic stress, as is expression of these genes. In contrast, TGA1a apparently does not bind in vivo to functional as-1 elements in promoters of PR-1a and PG13, genes whose expression is insensitive to this stimulus. The ®ndings here thus discriminate between a number of possible functional promoter binding sites for a trans-regulatory factor, within the context of a signal response pathway.