Investigating the regulation of one-carbon metabolism in Arabidopsis thaliana

Serine (Ser) biosynthesis in C(3) plants can occur via several pathways. One major route involves the tetrahydrofolate (THF)-dependent activities of the glycine decarboxylase complex (GDC, EC 2.1.1.10) and serine hydroxymethyltransferase (SHMT, EC 2.1.2.1) with glycine (Gly) as one-carbon (1-C) source. An alternative THF-dependent pathway involves the C1-THF synthase/SHMT activities with formate as 1-C source. Here, we have investigated aspects of the regulation of these two folate-mediated pathways in Arabidopsis thaliana (L.) Heynh. Columbia using two approaches. Firstly, transgenic plants overexpressing formate dehydrogenase (FDH, EC 1.2.1.2) were used to continue our previous studies on the function of FDH in formate metabolism. The formate pool size was approximately 73 nmol (g FW)(-1) in wild type (WT) Arabidopsis plants; three independent transgenic lines had similar-sized pools of formate. Transgenic plants produced more (13)CO(2) from supplied [(13)C]formate than did WT plants but were not significantly different from WT plants in their synthesis of Ser. We concluded that FDH has no direct role in the regulation of the above two pathways of Ser synthesis; the breakdown of formate to CO(2) by the FDH reaction is the primary and preferred fate of the organic acid in Arabidopsis. The ratio between the GDC/SHMT and C1-THF synthase/SHMT pathways of Ser synthesis from [alpha-(13)C]Gly and [(13)C]formate, respectively, in Arabidopsis shoots was 21 : 1; in roots, 9 : 1. In shoots, therefore, the pathway from formate plays only a small role in Ser synthesis; in the case of roots, results indicated that the 9 : 1 ratio was as a result of greater fluxes of (13)C through both pathways together with a relatively higher contribution from the C1-THF synthase/SHMT route than in shoots. We also examined the synthesis of Ser in a GDC-deficient mutant of Arabidopsis (glyD) where the GDC/SHMT pathway was impaired. Compared with WT, glyD plants accumulated 5-fold more Gly than WT after supplying [alpha-(13)C]Gly for 24 h; the accumulation of Ser from [alpha-(13)C]Gly was reduced by 25% in the same time period. On the other hand, the accumulation of Ser through the C1-THF synthase/SHMT pathway in glyD plants was 2.5-fold greater than that in WT plants. Our experiments confirmed that the GDC/SHMT and C1-THF synthase/SHMT pathways normally operate independently in Arabidopsis plants but that when the primary GDC/SHMT pathway is impaired the alternative C1-THF synthase/SHMT pathway can partially compensate for deficiencies in the synthesis of Ser.     

Desktop prediction/analysis of mass spectrometric data in proteomic projects by using massXpert

With the ever-increasing demand for biopolymer mass spectrometry, specialized software is needed to both predict and process mass spectrometric data. With massXpert, we present a proteomics-oriented program mainly concerned with protein physico-chemistry and protein/peptide mass spectra simulations. AVAILABILITY: The massXpert program is free for academic and commercial use at http://frl.lptc.u-bordeaux.fr. SUPPLEMENTARY INFORMATION: The http://frl.lptc.u-bordeaux.frsite contains a tutorial for online perusal or download.     

Utilization of Industrial Waste for the Production of Bio-Preservative from <Emphasis Type="Italic">Bacillus licheniformis</Emphasis> Me1 and Its Application in Milk and Milk-Based Food Products

The bio-preservative efficacy of a partially purified antibacterial peptide (ppABP) produced by Bacillus licheniformis Me1 in an economical medium developed using agro-industry waste was evaluated by direct application in milk and milk-based food products. The addition of ppABP in milk samples stored at 4 ± 2 °C and 28 ± 2 °C resulted in the growth inhibition of pathogens Listeria monocytogenes Scott A, Micrococcus luteus ATCC 9341, and Staphylococcus aureus FRI 722. The shelf life of milk samples with added ppABP increased to 4 days at 28 ± 2 °C, whereas curdling and off-odor were noticed in samples without ppABP. Furthermore, the milk samples with ppABP were sensorily acceptable. Antilisterial effect was also observed in cheese and paneer samples treated with ppABP. These results clearly indicate that the ppABP of B. licheniformis Me1 can be utilized as a bio-preservative to control the growth of spoilage and pathogenic bacteria, thereby reducing the risk of food-borne diseases.     

Do mental health professionals use diagnostic classifications the way we think they do? A global survey

We report on a global survey of diagnosing mental health professionals, primarily psychiatrists, conducted as a part of the development of the ICD‐11 mental and behavioural disorders classification. The survey assessed these professionals' use of various components of the ICD‐10 and the DSM, their attitudes concerning the utility of these systems, and usage of “residual” (i.e., “other” or “unspecified”) categories. In previous surveys, most mental health professionals reported they often use a formal classification system in everyday clinical work, but very little is known about precisely how they are using those systems. For example, it has been suggested that most clinicians employ only the diagnostic labels or codes from the ICD‐10 in order to meet administrative requirements. The present survey was conducted with clinicians who were members of the Global Clinical Practice Network (GCPN), established by the World Health Organization as a tool for global participation in ICD‐11 field studies. A total of 1,764 GCPN members from 92 countries completed the survey, with 1,335 answering the questions with reference to the ICD‐10 and 429 to the DSM (DSM‐IV, DSM‐IV‐TR or DSM‐5). The most frequent reported use of the classification systems was for administrative or billing purposes, with 68.1% reporting often or routinely using them for that purpose. A bit more than half (57.4%) of respondents reported often or routinely going through diagnostic guidelines or criteria systematically to determine whether they apply to individual patients. Although ICD‐10 users were more likely than DSM‐5 users to utilize the classification for administrative purposes, other differences were either slight or not significant. Both classifications were rated to be most useful for assigning a diagnosis, communicating with other health care professionals and teaching, and least useful for treatment selection and determining prognosis. ICD‐10 was rated more useful than DSM‐5 for administrative purposes. A majority of clinicians reported using “residual” categories at least sometimes, with around 12% of ICD‐10 users and 19% of DSM users employing them often or routinely, most commonly for clinical presentations that do not conform to a specific diagnostic category or when there is insufficient information to make a more specific diagnosis. These results provide the most comprehensive available information about the use of diagnostic classifications of mental disorders in ordinary clinical practice.     

The intracellular nucleotide‐binding leucine‐rich repeat receptor (SlNRC4a) enhances immune signalling elicited by extracellular perception

Plant recognition and defence against pathogens employs a two‐tiered perception system. Surface‐localized pattern recognition receptors (PRRs) act to recognize microbial features, whereas intracellular nucleotide‐binding leucine‐rich repeat receptors (NLRs) directly or indirectly recognize pathogen effectors inside host cells. Employing the tomato PRR LeEIX2/EIX model system, we explored the molecular mechanism of signalling pathways. We identified an NLR that can associate with LeEIX2, termed SlNRC4a (NB‐LRR required for hypersensitive response‐associated cell death‐4). Co‐immunoprecipitation demonstrates that SlNRC4a is able to associate with different PRRs. Physiological assays with specific elicitors revealed that SlNRC4a generally alters PRR‐mediated responses. SlNRC4a overexpression enhances defence responses, whereas silencing SlNRC4 reduces plant immunity. Moreover, the coiled‐coil domain of SlNRC4a is able to associate with LeEIX2 and is sufficient to enhance responses upon EIX perception. On the basis of these findings, we propose that SlNRC4a acts as a noncanonical positive regulator of immunity mediated by diverse PRRs. Thus, SlNRC4a could link both intracellular and extracellular immune perceptions.     

Tn5-Mediated Cloning of a Genetic Region from Pseudomonas putida Involved in the Stimulation of Plant Root Elongation

Transposon (Tn5) mutagenesis was applied to Pseudomonas putida GR12-2R3, which promotes root elongation (a phenotype designated Pre) of Brassica campestris under gnotobiotic conditions. Of 3,000 Tn5 transconjugants, only one mutant that lost Pre activity but remained prototrophic and capable of plant root colonization was detected. This mutant was complemented by plasmid pRE53, which contained a 15.0-kilobase DNA insert isolated from a parental strain. The complemented mutant regained full Pre activity comparable to that of the wild type.