The plasticity of NBS resistance genes in sorghum is driven by multiple evolutionary processes

Background Increased disease resistance is a key target of cereal breeding programs, with disease outbreaks continuing to threaten global food production, particularly in Africa. Of the disease resistance gene families, the nucleotide-binding site plus leucine-rich repeat (NBS-LRR) family is the most prevalent and ancient and is also one of the largest gene families known in plants. The sequence diversity in NBS-encoding genes was explored in sorghum, a critical food staple in Africa, with comparisons to rice and maize and with comparisons to fungal pathogen resistance QTL. Results In sorghum, NBS-encoding genes had significantly higher diversity in comparison to non NBS-encoding genes and were significantly enriched in regions of the genome under purifying and balancing selection, both through domestication and improvement. Ancestral genes, pre-dating species divergence, were more abundant in regions with signatures of selection than in regions not under selection. Sorghum NBS-encoding genes were also significantly enriched in the regions of the genome containing fungal pathogen disease resistance QTL; with the diversity of the NBS-encoding genes influenced by the type of co-locating biotic stress resistance QTL. Conclusions NBS-encoding genes are under strong selection pressure in sorghum, through the contrasting evolutionary processes of purifying and balancing selection. Such contrasting evolutionary processes have impacted ancestral genes more than species-specific genes. Fungal disease resistance hot-spots in the genome, with resistance against multiple pathogens, provides further insight into the mechanisms that cereals use in the “arms race” with rapidly evolving pathogens in addition to providing plant breeders with selection targets for fast-tracking the development of high performing varieties with more durable pathogen resistance.

Characterization of disease resistance gene candidates of the nucleotide binding site (NBS) type from banana and correlation of a transcriptional polymorphism with resistance to Fusarium oxysporum f.sp. cubense race 4

Most plant disease resistance (R) genes encode proteins with a nucleotide binding site and leucine-rich repeat structure (NBS-LRR). In this study, degenerate primers were used to amplify genomic NBS-type sequences from wild banana (Musa acuminata ssp. malaccensis) plants resistant to the fungal pathogen Fusarium oxysporum formae specialis (f. sp.) cubense (FOC) race 4. Five different classes of NBS-type sequences were identified and designated as resistance gene candidates (RGCs). The deduced amino acid sequences of the RGCs revealed the presence of motifs characteristic of the majority of known plant NBS-LRR resistance genes. Structural and phylogenetic analyses grouped the banana RGCs within the non-TIR (homology to Toll/interleukin-1 receptors) subclass of NBS sequences. Southern hybridization showed that each banana RGC is present in low copy number. The expression of the RGCs was assessed by RT-PCR in leaf and root tissues of plants resistant or susceptible to FOC race 4. RGC1, 3 and 5 showed a constitutive expression profile in both resistant and susceptible plants whereas no expression was detected for RGC4. Interestingly, RGC2 expression was found to be associated only to FOC race 4 resistant lines. This finding could assist in the identification of a FOC race 4 resistance gene.

The plasticity of NBS resistance genes in sorghum is driven by multiple evolutionary processes

Background Increased disease resistance is a key target of cereal breeding programs, with disease outbreaks continuing to threaten global food production, particularly in Africa. Of the disease resistance gene families, the nucleotide-binding site plus leucine-rich repeat (NBS-LRR) family is the most prevalent and ancient and is also one of the largest gene families known in plants. The sequence diversity in NBS-encoding genes was explored in sorghum, a critical food staple in Africa, with comparisons to rice and maize and with comparisons to fungal pathogen resistance QTL. Results In sorghum, NBS-encoding genes had significantly higher diversity in comparison to non NBS-encoding genes and were significantly enriched in regions of the genome under purifying and balancing selection, both through domestication and improvement. Ancestral genes, pre-dating species divergence, were more abundant in regions with signatures of selection than in regions not under selection. Sorghum NBS-encoding genes were also significantly enriched in the regions of the genome containing fungal pathogen disease resistance QTL; with the diversity of the NBS-encoding genes influenced by the type of co-locating biotic stress resistance QTL. Conclusions NBS-encoding genes are under strong selection pressure in sorghum, through the contrasting evolutionary processes of purifying and balancing selection. Such contrasting evolutionary processes have impacted ancestral genes more than species-specific genes. Fungal disease resistance hot-spots in the genome, with resistance against multiple pathogens, provides further insight into the mechanisms that cereals use in the “arms race” with rapidly evolving pathogens in addition to providing plant breeders with selection targets for fast-tracking the development of high performing varieties with more durable pathogen resistance.

Synthesis of Thioesters by Simultaneous Activation of Carboxylic Acids and Alcohols Using PPh3/NBS with Benzyltriethylammonium Tetrathiomolybdate as the Sulfur Transfer Reagent

A new and simple route for the synthesis of thioesters starting from carboxylic acids and alcohols is reported by using tetrathiomolybdate as the key sulfur transfer reagent. Triphenylphosphane and N-bromosuccinimide were used for the activation of the carboxylic acid and alcohol in the same pot followed by the transfer of sulfur from tetrathiomolybdate. Thioesters were obtained in good to moderate yields. Primary alcohols show excellent reactivity and gave good yields of the corresponding thioesters, whereas secondary alcohols gave moderate yields and tertiary alcohols were very less reactive and gave poor yields of the corresponding thioesters.

Modifications to the Suzuki reaction and mechanistic insights on the NBS mediated cleavage of benzylidene acetals /

One of the most challenging tasks for a synthetic organic chemist today, is the development of chemo, regio, and stereoselective methodologies toward the total synthesis of macromolecules. r . The objective of my thesis was to develop methodologies towards this end. The first part of my project was to develop highly functionalized chirons from D-glucose, a cheap, chiral starting material, to be utilized in this capacity. The second part of the project dealt with modifying the carbon-carbon bond forming Suzuki reaction, which is utilized quite often as a means of combining molecular sub units in total synthesis applications. As previously stated the first area of the project was to develop high value chirons from D-glucose, but the mechanism of their formation was also investigated. The free radical initiated oxidative fragmentation of benzylidene acetals was investigated through the use of several test-case substrates in order to unravel the possible mechanistic pathways. This was performed by reacting the different acetals with N-bromosuccinimide and benzoyl peroxide in chlorobenzene at 70^C in all cases. Of the three mechanistic pathways discussed in the literature, it was determined, from the various reaction products obtained, that the fragmentation of the initial benzylic radical does not occur spontaneously but rather, oxidation proceeds to give the benzyl bromide, which then fragments via a polar pathway. It was also discovered that the regioselectivity of the fragmentation step could be altered through incorporation of an allylic system into the benzylidene acetal. This allows for the acquisition of a new set of densely functionalized. chiral, valuable synthetic intermediates in only a few steps and in high yields from a-Dglucose. The second part of the project was the utilization of the phosphonium salt room temperature ionic liquid tetradecyltrihexylphosphonium chloride (THPC) as an efficient reusable medium for the palladium catalyzed Suzuki cross-coupling reaction of aryl halides, including aryl chlorides, under mild conditions. The cross-coupling reactions were found to proceed in THPC containing small amounts of water and toluene using potassium phosphate and 1% Pd2(dba)3. Variously substituted iodobenzenes, including electron rich derivatives, reacted efficiently in THPC with a variety of arylboronic acids and afforded complete conversion within 1 hour at 50 ^C. The corresponding aryl bromides also reacted under these conditions with the addition of a catalytic amount of triphenylphosphine that allowed for complete conversion and high isolated yields. The reactions involving aryl chlorides were considerably slower, although the addition of triphenylphosphine and heating at 70 ^C allowed high conversion of electron deficient derivatives. Addition of water and hexane to the reaction products results in a triphasic system in which the top hexane phase contained the biaryl products, the palladium catalyst remained fully dissolved in the central THPC layer, while the inorganic salts were extracted into the lower aqueous phase. The catalyst was then recycled by removing the top and bottom layers and adding the reagents to the ionic liquid which was heated again at 50 ^C; resulting in complete turnover of iodobenzene. Repetition of this procedure gave the biphenyl product in 82-97% yield (repeated five times) for both the initial and recycled reaction sequences.

Síntese de acetato de celulose a partir da palha de feijão utilizando N-bromossuccinimida (NBS) como catalisador

Neste estudo a celulose obtida da palha de feijão foi utilizada para produzir um material hidrofóbico (acetato de celulose) para ser avaliado como absorvente de óleo. Nas reações de acetilação foram utilizados anidrido acético e dois catalisadores, a piridina (PY) e N-bromossuccinimida (NBS). Os materiais produzidos foram caracterizados por espectroscopia na região do infravermelho médio, microscopia eletrônica de varredura, difratometria de raios-X e análise elementar. O NBS mostrou-se mais eficiente que a PY e, seu uso resultou em materiais com maiores quantidades de grupos acetatos, mais hidrofóbicos e com maiores capacidades de absorção de óleo de soja.

(Fig. 3) Sepia officinalis standard metobolic rate and seawater pH (NBS) during experiments, 2008

Ocean acidification and associated changes in seawater carbonate chemistry negatively influence calcification processes and depress metabolism in many calcifying marine invertebrates. We present data on the cephalopod mollusc Sepia officinalis, an invertebrate that is capable of not only maintaining calcification, but also growth rates and metabolism when exposed to elevated partial pressures of carbon dioxide (pCO2). During a 6 wk period, juvenile S. officinalis maintained calcification under ~4000 and ~6000 ppm CO2, and grew at the same rate with the same gross growth efficiency as did control animals. They gained approximately 4% body mass daily and increased the mass of their calcified cuttlebone by over 500%. We conclude that active cephalopods possess a certain level of pre-adaptation to long-term increments in carbon dioxide levels. Our general understanding of the mechanistic processes that limit calcification must improve before we can begin to predict what effects future ocean acidification will have on calcifying marine invertebrates.

NBS computer user's guide /

Mode of access: Internet.

Measurements for the safe use of radiation : proceedings of an NBS 75th anniversary symposium held at the National Bureau of Standards, Gaithersburg, Maryland, March 1-4, 1976 /

Includes bibliographical references and index.

Research and innovation in the building regulatory process : proceedings of the first NBS/NCSBCS joint conference, held in Providence, Rhode Island, on September 21-22, 1976, in conjunction with the ninth annual meeting of the National Conference of States on Building Codes and Standards (NCSBCS), inc. /

Mode of access: Internet.

Test patterns NBS-28 and NBS-28A : random fault interconnect step coverage and other structures /

S/N 003-003-02297-7.

ARPA/NBS workshop III : test patterns for integrated circuits /

Consists of synopses of talks and discussions presented at the workshop held Sept. 6, 1974 in Scottsdale, Ariz.

Hydrocarbons for fuel--75 years of materials research at NBS /

Includes bibliographical references.