QTL mapping of stay-green in two sorghum recombinant inbred populations

The stay-green trait is a reported component of tolerance to terminal drought stress in sorghum. To map quantitative trait loci (QTLs) for stay-green, two sorghum recombinant inbred populations (RIPs) of 226 F(3:5) lines each were developed from crosses (1) IS9830 x E36-1 and (2) N13 x E36-1. The common parental line, E36-1 of Ethiopian origin, was the stay-green trait source. The genetic map of RIP 1 had a total length of 1,291 cM, with 128 markers (AFLPs, RFLPs, SSRs and RAPDs) distributed over ten linkage groups. The map of RIP 2 spanned 1,438 cM and contained 146 markers in 12 linkage groups. The two RIPs were evaluated during post-rainy seasons at Patancheru, India, in 1999/2000 (RIP 2) and 2000/2001 (RIP 1). The measures of stay-green mapped were the green leaf area percentages at 15, 30 and 45 days after flowering (% GL15, % GL30 and % GL45, respectively). Estimated repeatabilities for % GL15, % GL30 and % GL45 amounted to 0.89, 0.81 and 0.78 in RIP 1, and 0.91, 0.88 and 0.85 in RIP 2, respectively. The number of QTLs for the three traits detected by composite interval mapping ranged from 5 to 8, explaining 31% to 42% of the genetic variance. In both RIPs, both parent lines contributed stay-green alleles. Across the three measures of the stay-green trait, three QTLs on linkage groups A, E and G were common to both RIPs, with the stay-green alleles originating from E36-1. These QTLs were therefore consistent across the tested genetic backgrounds and years. After QTL validation across sites and verification of the general benefit of the stay-green trait for grain yield performance and stability in the target areas, the corresponding chromosomal regions could be candidates for marker-assisted transfer of stay-green into elite materials.     

Implications of aromatic–aromatic interactions: From protein structures to peptide models

With increasing structural information on proteins, the opportunity to understand physical forces governing protein folding is also expanding. One of the significant non‐covalent forces between the protein side chains is aromatic–aromatic interactions. Aromatic interactions have been widely exploited and thoroughly investigated in the context of folding, stability, molecular recognition, and self‐assembly processes. Through this review, we discuss the contribution of aromatic interactions to the activity and stability of thermophilic, mesophilic, and psychrophilic proteins. Being hydrophobic, aromatic amino acids tend to reside in the protein hydrophobic interior or transmembrane segments of proteins. In such positions, it can play a diverse role in soluble and membrane proteins, and in α‐helix and β‐sheet stabilization. We also highlight here some excellent investigations made using peptide models and several approaches involving aryl–aryl interactions, as an increasingly popular strategy in protein and peptide engineering. A recent survey described the existence of aromatic clusters (trimer, tetramer, pentamer, and higher order assemblies), revealing the self‐associating property of aryl groups, even in folded protein structures. The application of this self‐assembly of aromatics in the generation of modern bionanomaterials is also discussed.     

Insights on inhibition of Plasmodium falciparum plasmepsin I by novel epoxyazadiradione derivatives – molecular docking and comparative molecular field analysis

In the present study, we have explored the anti-malarial potential of epoxyazadiradione, the natural entity extracted from the neem seed oil and its chemical derivatives, against Plasmodium falciparum. The Surflex dock analysis of 41 compounds against an indispensable target, plasmepsin I (PM-I) revealed that around 70% of the compounds are found to have good binding capacity with the consensus score (C-score) of 5 to 4 with few hydrogen bonds. To elucidate the major structural requirements, vital for binding with the plasmepsin enzyme and to develop the predictive models, three-dimentional quantitative structural activity relationship (3D-QSAR) – comparative molecular field analysis (CoMFA) was carried out using Sybyl X.0. Robust and predictive models were obtained with cross-validated correlation coefficient (q²) value of 0.967 and the non-cross-validated correlation coefficient (r²) value of 0.825, which were validated by an external test set with the predictive correlation coefficient r²_(pred) values of 0.773. Three zones were identified for substitution with bulky groups and one zone for substitution with non-bulky groups. Three positions favouring the electronegative group substitution and one for the electropositive group substitution were identified. The physicochemical properties of ligands with the highest C-score were studied.

Communicated by Ramaswamy H. Sarma     

Role of calcium–calmodulin in auxin-induced somatic embryogenesis in leaf base cultures of wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> var. HD 2329)

Wheat leaf bases cultured for 1 day on 2,4-d (10 μM) display the induction of somatic embryogenesis. The induction of somatic embryogenesis by 2,4-d appears to be calcium-mediated as treatment of leaf bases with the calcium chelator, EGTA, prior to 2,4-d treatment, inhibited the induction of somatic embryogenesis. This sensitivity of auxin to reduced calcium levels can be reversed by calcium ions alone and not any other divalent cation like magnesium or zinc. Additionally, the expression of the three calcium-regulated genes, Triticum aestivum calmodulin binding protein kinase, calcium-dependent protein kinase, and putative calcium binding protein was analyzed in wheat leaf bases which suggest a specific role for Ca²⁺ in somatic embryogenesis. Application of the calcium ionophore, A23187, either alone or along with 2,4-d, induced somatic embryogenesis. This specificity for calcium was verified both by treatment with the calcium antagonist TMB8, and the elimination of calcium from the medium, resulting in reduction of somatic embryogenesis by 80%. Treatment with calcium channel blockers like verapamil and nifedipine, calcium antagonist, lanthanum, and calmodulin inhibitors chlorpromazine and fluphenazine, prior to the 2,4-d treatment, inhibited induction of somatic embryogenesis. The present study thus provides evidence for the involvement of calcium–calmodulin in the stimulus–response coupling of auxin-induced somatic embryogenesis in wheat leaf base system.     

Low-cost media for <Emphasis Type="Italic">in vitro</Emphasis> conservation of turmeric (<Emphasis Type="Italic">Curcuma longa L.</Emphasis>) and genetic stability assessment using RAPD markers

Up to 73% decrease in cost of media for plant regeneration and in vitro conservation was achieved in Curcuma longa cv Prathibha by using inexpensive carbon source and gelling agent. Laboratory reagent-grade sucrose was replaced by locally available commercial sugar (market sugar or sugar cubes) as carbon source and bacteriological grade agar by isabgol (also named isubgol) as gelling agent. No adverse effects on shoot regeneration and conservation on isabgol-gelled low-cost media were observed as compared to that on agar-gelled control medium (CM). Some 33–56% cultures of C. longa survived up to 12 mo. on isabgol-gelled medium in comparison to only 16% on CM. Genetic stability of 12-month-old in vitro-conserved plants was assessed using 25 random amplified polymorphic DNA (RAPD) primers; no significant variation was observed in RAPD profiles of mother plants and in vitro-conserved plantlets on CM and low-cost media.     

An altered FtsA can compensate for the loss of essential cell division protein FtsN in Escherichia coli

FtsN is the last known essential protein component to be recruited to the Escherichia coli divisome, and has several special properties. Here we report the isolation of suppressor mutants of ftsA that allow viability in the absence of ftsN. Cells producing the FtsA suppressors exhibited a mild cell division deficiency in the absence of FtsN, and no obvious phenotype in its presence. Remarkably, these altered FtsA proteins also could partially suppress a deletion of ftsK or zipA, were less toxic than wild-type FtsA when in excess, and conferred resistance to excess MinC, indicating that they share some properties with the previously isolated FtsA* suppressor mutant, and bypass the need for ftsN by increasing the integrity of the Z ring. TolA, which normally requires FtsN for its recruitment to the divisome, localized proficiently in the suppressed ftsN null strain, strongly suggesting that FtsN does not recruit the Tol-Pal complex directly. Therefore, despite its classification as a core divisome component, FtsN has no unique essential function but instead promotes overall Z ring integrity. The results strongly suggest that FtsA is conformationally flexible, and this flexibility is a key modulator of divisome function at all stages.     

Munc13-4 interacts with syntaxin 7 and regulates late endosomal maturation,endosomal signaling,and TLR9-initiated cellular responses

The molecular mechanisms that regulate late endosomal maturation and function are not completely elucidated, and direct evidence of a calcium sensor is lacking. Here we identify a novel mechanism of late endosomal maturation that involves a new molecular interaction between the tethering factor Munc13-4, syntaxin 7, and VAMP8. Munc13-4 binding to syntaxin 7 was significantly increased by calcium. Colocalization of Munc13-4 and syntaxin 7 at late endosomes was demonstrated by high-resolution and live-cell microscopy. Munc13-4–deficient cells show increased numbers of significantly enlarged late endosomes, a phenotype that was mimicked by the fusion inhibitor chloroquine in wild-type cells and rescued by expression of Munc13-4 but not by a syntaxin 7–binding–deficient mutant. Late endosomes from Munc13-4-KO neutrophils show decreased degradative capacity. Munc13-4–knockout neutrophils show impaired endosomal-initiated, TLR9-dependent signaling and deficient TLR9-specific CD11b up-regulation. Thus we present a novel mechanism of late endosomal maturation and propose that Munc13-4 regulates the late endocytic machinery and late endosomal–associated innate immune cellular functions.     

Mazindol Attenuates the 3,4-Methylenedioxymethamphetamine-Induced Formation of Hydroxyl Radicals and Long-Term Depletion of Serotonin in the Striatum

The formation of hydroxyl radicals following the systemic administration of 3,4-methylenedioxymethamphetamine (MDMA) was studied in the striatum of the rat by quantifying the stable adducts of salicylic acid and D-phenylalanine, namely, 2,3-dihydroxybenzoic acid (2,3-DHBA) and p-tyrosine, respectively. The repeated administration of MDMA produced a sustained increase in the extracellular concentration of 2,3-DHBA and p-tyrosine, as well as dopamine. The MDMA-induced increase in the extracellular concentration of both dopamine and 2,3-DHBA was suppressed in rats treated with mazindol, a dopamine uptake inhibitor. Mazindol also attenuated the long-term depletion of serotonin (5-HT) in the striatum produced by MDMA without altering the acute hyperthermic response to MDMA. These results are supportive of the view that MDMA produces a dopamine-dependent increase in the formation of hydroxyl radicals in the striatum that may contribute to the mechanism whereby MDMA produces a long-term depletion of brain 5-HT content.     

Use of Commercial Sugar, Isabgol and Ordinary Water in Culture Medium for Conservation of Curcuma longa L

Commercial sugar (market sugar or cube sugar) as carbon source, psyllium seed hask commonly known as isabgol (Plantago ovata) as gelling agent, and medium prepared in ordinary water [OW; pH: 7.48; electrical conductivity (EC): 299 μS cm^?1] instead of deionized distilled water (DW; pH: 5.67; EC: 5 μS cm^?1), did not show any significant effect on micropropagation and in vitro conservation of Curcuma longa cv Prathibha as compared to the control medium (CM) that was prepared with sucrose, gelled with agar in DW. The isabgol-gelled media not only supported better survival of cultures than those on agargelled media, but was also very cost-effective. After 12 months of conservation, significantly higher survival of 33–44% cultures was recorded in isabgol-gelled media, whereas only 16% of cultures survived on CM. By substituting inexpensive sources of three major components of the medium — market sugar, isabgol and OW, up to 84% decrease in cost of medium for plant regeneration and in vitro conservation could be achieved.