Bioevaluation of Subabul (Leucaena leucocephala) proteinase inhibitors on Helicoverpa armigera

Helicoverpa armigera, a highly polyphagous pest, has a broad host spectrum, causes significant levels of yield loss in many agriculturally important crops. Serine primarily responsible for most of the proteolytic activity in the larval gut of lepidopteron insects. Neonate larvae were reared on artificial diet and chickpea seeds smeared with Subabul Trypsin Inhibitor. Larvae fed with artificial diet showed reduction in larval weight up to 21% (HSTI) and 43% (LSTI). However, larvae fed on seeds showed significant reduction in weight, 52.4% (HSTI) and 60.3% (LSTI), suggesting that the diet also plays a vital role on the effectiveness of the inhibitors on larval growth and development. HSTI and LSTI inhibited the gut proteinases from larvae fed on artificial diet significantly (41.40% and 64.36%) compared to the gut proteinases (27.80% and 38.90%) from larvae fed on chickpea seeds. Seeds smeared with 10,000 TIU resulted in complete mortality of larvae while there was no mortality observed in artificial diet. The results reveal that LSTI is a stronger inhibitor of insect gut proteinases and for larvae fed with poor nutrition in the natural ecosystems, low level expression of inhibitor would be enough to affect the growth and development. Handling editor: Chen-Zhu Wang     

Lysine propionylation and butyrylation are novel post-translational modifications in histones

The positively charged lysine residue plays an important role in protein folding and functions. Neutralization of the charge often has a profound impact on the substrate proteins. Accordingly all the known post-translational modifications at lysine have pivotal roles in cell physiology and pathology. Here we report the discovery of two novel, in vivo lysine modifications in histones, lysine propionylation and butyrylation. We confirmed, by in vitro labeling and peptide mapping by mass spectrometry, that two previously known acetyltransferases, p300 and CREB-binding protein, could catalyze lysine propionylation and lysine butyrylation in histones. Finally p300 and CREB-binding protein could carry out autopropionylation and autobutyrylation in vitro. Taken together, our results conclusively establish that lysine propionylation and lysine butyrylation are novel post-translational modifications. Given the unique roles of propionyl-CoA and butyryl-CoA in energy metabolism and the significant structural changes induced by the modifications, the two modifications are likely to have important but distinct functions in the regulation of biological processes.     

A high density GBS map of bread wheat and its application for dissecting complex disease resistance traits

Background

Genotyping-by-sequencing (GBS) is a high-throughput genotyping approach that is starting to be used in several crop species, including bread wheat. Anchoring GBS tags on chromosomes is an important step towards utilizing them for wheat genetic improvement. Here we use genetic linkage mapping to construct a consensus map containing 28644 GBS markers.

Results

Three RIL populations, PBW343 × Kingbird, PBW343 × Kenya Swara and PBW343 × Muu, which share a common parent, were used to minimize the impact of potential structural genomic variation on consensus-map quality. The consensus map comprised 3757 unique positions, and the average marker distance was 0.88 cM, obtained by calculating the average distance between two adjacent unique positions. Significant variation of segregation distortion was observed across the three populations. The consensus map was validated by comparing positions of known rust resistance genes, and comparing them to wheat reference genome sequences recently published by the International Wheat Genome Sequencing Consortium, Rye and Ae. tauschii genomes. Three well-characterized rust resistance genes (Sr58/Lr46/Yr29, Sr2/Yr30/Lr27, and Sr57/Lr34/Yr18) and 15 published QTLs for wheat rusts were validated with high resolution. Fifty-two per cent of GBS tags on the consensus map were successfully aligned through BLAST to the right chromosomes on the wheat reference genome sequence.

Conclusion

The consensus map should provide a useful basis for analyzing genome-wide variation of complex traits. The identified genes can then be explored as genetic markers to be used in genomic applications in wheat breeding.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1424-5) contains supplementary material, which is available to authorized users.     

Evaluation of seed dressing and soil application formulations of Trichoderma species for integrated management of dry root rot of chickpea

The efficacy of the newly developed seed dressing and soil application formulations of Trichoderma viride, T. virens and T. harzianum were evaluated individually and in combinations under pot and field experiments for the management of dry root rot (Rhizoctonia bataticola) of chickpea (Cicer arientinum). In pot experiments, T. harzianum based seed dressing formulation, Pusa 5SD, and soil application formulations, Pusa Biogranule 5 (PBG 5) and Pusa Biopellet 10G (PBP 10G), were found to be effective in reducing dry root rot incidence in chickpea and increasing the seed germination, shoot and root lengths of the crop. Under field experiments, a combination of soil application of T. harzianum based PBP 10G and seed treatment with Pusa 5SD+carboxin was found to be the best by providing the highest seed germination, shoot and root lengths and grain yield and the lowest dry root rot incidence in chickpea.     

Microsatellite mapping identifies TTKST-effective stem rust resistance gene in wheat cultivars VL404 and Janz

Wheat cultivar VL404 carries seedling resistance to Puccinia graminis f. sp. tritici pathotype TTKST. Monogenic segregation for seedling resistance was observed in a VL404/WL711 recombinant inbred line population and the resistance locus was temporarily designated SrVL. Bulked segregant analysis using Diversity Arrays Technology markers located SrVL on chromosome 2BL. Detailed simple sequence repeat mapping placed SrVL between gwm120 and wmc175, both at genetic distances of 3.3 cM. Based on adult plant responses of Janz and VL404 in India and Kenya, we expected these cultivars to carry the same gene against TTKST. A subset of Diamondbird/Janz doubled haploid (DH) population showed monogenic segregation, when tested against TTKST and the locus was temporarily named SrJNZ. SrVL-linked markers gwm120 and wmc175 flanked SrJNZ at a similar genetic distance, thereby confirming our hypothesis. Chromosome 2BL carries Sr9, Sr16 and Sr28. Sr9 is a multi-allelic locus and all known alleles of Sr9 and Sr16 are ineffective against TTKSK and its derivatives. A recombination value of 16.7 cM between Sr9g-linked stripe rust resistance gene Yr7 and SrJNZ in Diamondbird/Janz DH population suggested that SrJNZ is not an allele at the Sr9 locus. Based on comparison of published genetic distances between Lr13, Sr9, Sr28 and Sr16 with that observed in this study, we concluded SrVL and SrJNZ to be Sr28. This gene was contributed by a common parent Gabo, which also exhibited resistance against TTKST. Sr28-linked markers gwm120 and wmc175 confirmed the presence of this gene in a high proportion of Australian cultivars that showed stem rust resistance in Kenya. These markers can be used for marker-assisted pyramiding of Sr28 with other stem rust resistance genes.     

Role of Lys-226 in the catalytic mechanism of Bacillus stearothermophilus serine hydroxymethyltransferase--crystal structure and kinetic studies

Serine hydroxymethyltransferase (SHMT), a pyridoxal 5'-phosphate (PLP)-dependent enzyme catalyzes the reversible conversion of l-Ser and tetrahydropteroylglutamate (H(4)PteGlu) to Gly and 5,10-methylene tetrahydropteroylglutamate (CH(2)-H(4)PteGlu). Biochemical and structural studies on this enzyme have implicated several residues in the catalytic mechanism, one of them being the active site lysine, which anchors PLP. It has been proposed that this residue is crucial for product expulsion. However, in other PLP-dependent enzymes, the corresponding residue has been implicated in the proton abstraction step of catalysis. In the present investigation, Lys-226 of Bacillus stearothermophilus SHMT (bsSHMT) was mutated to Met and Gln to evaluate the role of this residue in catalysis. The mutant enzymes contained 1 mol of PLP per mol of subunit suggesting that Schiff base formation with lysine is not essential for PLP binding. The 3D structure of the mutant enzymes revealed that PLP was bound at the active site in an orientation different from that of the wild-type enzyme. In the presence of substrate, the PLP ring was in an orientation superimposable with that of the external aldimine complex of wild-type enzyme. However, the mutant enzymes were inactive, and the kinetic analysis of the different steps of catalysis revealed that there was a drastic reduction in the rate of formation of the quinonoid intermediate. Analysis of these results along with the crystal structures suggested that K-226 is responsible for flipping of PLP from one orientation to another which is crucial for H(4)PteGlu-dependent Calpha-Cbeta bond cleavage of l-Ser.     

Behaviour of Aspergillus flavus in presence of Aspergillus niger during biosynthesis of aflatoxin B1

Aspergillus niger or Aspergillus tamarii when grown as mixed cultures with toxigenic A. flavus inhibits biosynthesis of aflatoxin by A. flavus, owing primarily to its ability to produce inhibitors of aflatoxin biosynthesis and to their ability to degrade aflatoxin. Gluconic acid partly prevents aflatoxin production. The other factors such as changes in pH of the medium and the effect on the growth of A. flavus have no role in imparting capabilities to these cultures to inhibit aflatoxin production by A. flavus.     

Genome-wide association study of stem rust resistance in a world collection of cultivated barley

Key message

QTL conferring a 14–40% reduction in adult plant stem rust severity to multiple races of Pgt were found on chromosome 5H and will be useful in barley breeding.

Abstract

Stem rust, caused by Puccinia graminis f. sp. tritici (Pgt) is an important disease of barley. The resistance gene Rpg1 has protected the crop against stem rust losses for over 70 years in North America, but is not effective against the African Pgt race TTKSK (and its variants) nor the domestic race QCCJB. To identify resistance to these Rpg1-virulent races, the Barley iCore Collection, held by the United States Department of Agriculture-Agricultural Research Service National Small Grains Collection was evaluated for adult plant resistance (APR) and seedling resistance to race TTKSK and APR to race QCCJB and the Pgt TTKSK composite of races TTKSK, TTKST, TTKTK, and TTKTT. Using a genome-wide association study approach based on 6224 single nucleotide polymorphic markers, seven significant loci for stem rust resistance were identified on chromosomes 1H, 2H, 3H, and 5H. The most significant markers detected were 11_11355 and SCRI_RS_177017 at 71–75 cM on chromosome 5H, conferring APR to QCCJB and TTKSK composite. Significant markers were also detected for TTKSK seedling resistance on chromosome 5H. All markers detected on 5H were independent of the rpg4/Rpg5 complex at 152–168 cM. This study verified the importance of the 11_11355 locus in conferring APR to races QCCJB and TTKSK and suggests that it may be effective against other races in the Ug99 lineage.

     

Genome-wide association mapping for resistance to leaf rust,stripe rust and tan spot in wheat reveals potential candidate genes

Key message

Genome-wide association mapping in conjunction with population sequencing map and Ensembl plants was used to identify markers/candidate genes linked to leaf rust, stripe rust and tan spot resistance in wheat.

Abstract

Leaf rust (LR), stripe rust (YR) and tan spot (TS) are some of the important foliar diseases in wheat (Triticum aestivum L.). To identify candidate resistance genes for these diseases in CIMMYT’s (International Maize and Wheat Improvement Center) International bread wheat screening nurseries, we used genome-wide association studies (GWAS) in conjunction with information from the population sequencing map and Ensembl plants. Wheat entries were genotyped using genotyping-by-sequencing and phenotyped in replicated trials. Using a mixed linear model, we observed that seedling resistance to LR was associated with 12 markers on chromosomes 1DS, 2AS, 2BL, 3B, 4AL, 6AS and 6AL, and seedling resistance to TS was associated with 14 markers on chromosomes 1AS, 2AL, 2BL, 3AS, 3AL, 3B, 6AS and 6AL. Seedling and adult plant resistance (APR) to YR were associated with several markers at the distal end of chromosome 2AS. In addition, YR APR was also associated with markers on chromosomes 2DL, 3B and 7DS. The potential candidate genes for these diseases included several resistance genes, receptor-like serine/threonine-protein kinases and defense-related enzymes. However, extensive LD in wheat that decays at about 5?×?10⁷ bps, poses a huge challenge for delineating candidate gene intervals and candidates should be further mapped, functionally characterized and validated. We also explored a segment on chromosome 2AS associated with multiple disease resistance and identified seventeen disease resistance linked genes. We conclude that identifying candidate genes linked to significant markers in GWAS is feasible in wheat, thus creating opportunities for accelerating molecular breeding.