The cyanelle genome of Cyanophora paradoxa, unlike the chloroplast genome, codes for the ribosomal L3 protein.

We describe a 1132 bp sequence of the cyanelle genome of Cyanophora paradoxa containing the rpl3 gene. This gene, which is not chloroplast encoded in plants, is the first of a long cyanelle ribosomal operon whose organization resembles that of the S10 operon of E. coli. We have shown that the rpl3 gene is transcribed in cyanelles as a 7500 nucleotide precursor and that the 5'-end of the mRNA starts approximately 90 nucleotides upstream from the initiation codon. However, no typical procaryotic promoter could be found for this gene. We have detected, using anti E. coli L3 antibodies, the cyanelle L3 protein in cyanelle extracts and in E. coli cells transformed with the cyanelle rpl3 gene.     

A 2.6 kb intron separates the signal peptide coding sequence of an anther-specific protein from the rest of the gene in sunflower

Summary Metabolism of sulfonylurea herbicides by Streptomyces griseolus ATCC 11796 is carried out via two cytochromes P-450, P-450_SU1 and P-450_SU2. Mutants of S. griseolus, selected by their reduced ability to metabolize a fluorescent sulfonylurea, do not synthesize cytochrome P-450_SU1 when grown in the presence of sulfonylureas. Genetic evidence indicated that this phenotype was the result of a deletion of > 15 kb of DNA, including the structural genes for cytochrome P-450_SU1 and an associated ferredoxin Fd-1 (suaC and suaB, respectively). In the absence of this monooxygenase system, the mutants described here respond to the presence of sulfonylureas or phenobarbital in the growth medium with the expression of only the suhC,B gene products (cytochrome P-450_SU2 and Fd-2), previously observed only as minor components in wild-type cells treated with sulfonylurea. These strains have enabled an analysis of sulfonylurea metabolism mediated by cytochrome P-450_SU2 in the absence of P-450_SU1, yielding an in vivo delineation of the roles of the two different cytochrome P-450 systems in herbicide metabolism by S. griseolus.     

Anther-specific,developmentally regulated expression of genes encoding a new class of proline-rich proteins in sunflower

We have used RNA gel blot analysis to demonstrate the anther-specific expression of three genes in sunflower. Expression of these genes was first detected shortly before flower opening, which occurs sequentially on the sunflower inflorescence, and continues during pollination. In contrast, these genes are not expressed (or only weakly expressed) in a male-sterile line in which anther development aborts. In situ hybridization experiments showed that these genes are only expressed in the single cell layer of the sunflower anther epidermis. In the case of one of these genes, which codes for an abundant mRNA, we report the peptide sequences deduced from the sequence of two similar but non identical cDNAs. These proteins contain a potential signal peptide and are characterized by the presence of a proline-rich region which reads KPSTPAPPPPPP(PP)K. Our results also suggest that several proline-rich proteins of unknown functions are specifically synthesized during the maturation of anthers in sunflower.     

The pollen-specific LIM protein PLIM-1 from sunflower binds nucleic acids in vitro

The protein PLIM-1 (formerly SF3) from sunflower is expressed exclusively in mature, free pollen. It contains two LIM domains associated with an acidic C-terminus comprising six copies of the pentapeptide motif (A,T,S) (E,D) TQN. We have expressed the pollen protein as well as some of its mutant forms inEscherichia coli and have used the bacterially produced proteins to study interactions with nucleic acids. Our studies show that the protein binds DNA and RNA in vitro to form large complexes, while mutant polypeptides containing either a single LIM domain or a destabilized first or second LIM domain do not. Although these data suggest that the biological function of PLIM-1 involves interactions with nucleic acids, its role in pollen development remains unclear.     

Cytochrome P450 CYP89A9 Is Involved in the Formation of Major Chlorophyll Catabolites during Leaf Senescence in Arabidopsis

Nonfluorescent chlorophyll catabolites (NCCs) were described as products of chlorophyll breakdown in Arabidopsis thaliana. NCCs are formyloxobilin-type catabolites derived from chlorophyll by oxygenolytic opening of the chlorin macrocycle. These linear tetrapyrroles are generated from their fluorescent chlorophyll catabolite (FCC) precursors by a nonenzymatic isomerization inside the vacuole of senescing cells. Here, we identified a group of distinct dioxobilin-type chlorophyll catabolites (DCCs) as the major breakdown products in wild-type Arabidopsis, representing more than 90% of the chlorophyll of green leaves. The molecular constitution of the most abundant nonfluorescent DCC (NDCC), At-NDCC-1, was determined. We further identified cytochrome P450 monooxygenase CYP89A9 as being responsible for NDCC accumulation in wild-type Arabidopsis; cyp89a9 mutants that are deficient in CYP89A9 function were devoid of NDCCs but accumulated proportionally higher amounts of NCCs. CYP89A9 localized outside the chloroplasts, implying that FCCs occurring in the cytosol might be its natural substrate. Using recombinant CYP89A9, we confirm FCC specificity and show that fluorescent DCCs are the products of the CYP89A9 reaction. Fluorescent DCCs, formed by this enzyme, isomerize to the respective NDCCs in weakly acidic medium, as found in vacuoles. We conclude that CYP89A9 is involved in the formation of dioxobilin-type catabolites of chlorophyll in Arabidopsis.     

Does P-Cresylglucuronide Have the Same Impact on Mortality as Other Protein-Bound Uremic Toxins?

Background

Uremic toxins are emerging as important, non-traditional cardiovascular risk factors in chronic kidney disease (CKD). P-cresol has been defined as a prototype protein-bound uremic toxin. Conjugation of p-cresol creates p-cresylsulfate (PCS) as the main metabolite and p-cresylglucuronide (PCG), at a markedly lower concentration. The objective of the present study was to evaluate serum PCG levels, determine the latter’s association with mortality and establish whether the various protein-bound uremic toxins (i.e. PCS, PCG and indoxylsulfate (IS)) differed in their ability to predict mortality.

Methodology/Principal Findings

We studied 139 patients (mean ± SD age: 67±12; males: 60%) at different CKD stages (34.5% at CKD stages 2–3, 33.5% at stage 4–5 and 32% at stage 5D). A recently developed high-performance liquid chromatography method was used to assay PCG concentrations. Total and free PCG levels increased with the severity of CKD. During the study period (mean duration: 779±185 days), 38 patients died. High free and total PCG levels were correlated with overall and cardiovascular mortality independently of well-known predictors of survival, such as age, vascular calcification, anemia, inflammation and (in predialysis patients) the estimated glomerular filtration rate. In the same cohort, free PCS levels and free IS levels were both correlated with mortality. Furthermore, the respective predictive powers of three Cox multivariate models (free PCS+other risk factors, free IS+other risk factors and free PCS+other risk factors) were quite similar - suggesting that an elevated PCG concentration has much the same impact on mortality as other uremic toxins (such as PCS or IS) do.

Conclusions

Although PCG is the minor metabolite of p-cresol, our study is the first to reveal its association with mortality. Furthermore, the free fraction of PCG appears to have much the same predictive power for mortality as PCS and IS do.