Association between presence of <Emphasis Type="Italic">Triticum timopheevii</Emphasis> introgression and D-genome retention in hexaploid/tetraploid wheat crosses

The 2G Triticum timopheevii introgression harbours genes for multiple disease resistance and quality traits in bread wheat. In order to transfer this segment from bread wheat into durum, the bread wheat line Sunguard, which carries this introgressed 2G segment was crossed with three tetraploid durum parents. A significant difference was observed in the segregation ratio of the 2G segment in the different crosses at the F₂ generation with two of the three populations indicating segregation distortion against the hexaploid 2G segment. In these populations, the presence of the 2G segment was strongly correlated with the presence of D-genome chromosomes. These results were confirmed in the F₄ generation of these populations. Six plants were identified in the F₄ generation, which had retained the introgressed 2G segment in a homozygous condition and did not have a complete D-genome set. Two of these lines only had two non-homologous D-genome chromosomes in the F₅ generation. Thus, the 2G segment and possibly other translocations can be transferred into durum wheat through hexaploid/tetraploid hybridisation.     

Plant-specific cation/H+ exchanger 17 and its homologs are endomembrane K+ transporters with roles in protein sorting

The complexity of intracellular compartments in eukaryotic cells evolved to provide distinct environments to regulate processes necessary for cell proliferation and survival. A large family of predicted cation/proton exchangers (CHX), represented by 28 genes in Arabidopsis thaliana, are associated with diverse endomembrane compartments and tissues in plants, although their roles are poorly understood. We expressed a phylogenetically related cluster of CHX genes, encoded by CHX15-CHX20, in yeast and bacterial cells engineered to lack multiple cation-handling mechanisms. Of these, CHX16-CHX20 were implicated in pH homeostasis because their expression rescued the alkaline pH-sensitive growth phenotype of the host yeast strain. A smaller subset, CHX17-CHX19, also conferred tolerance to hygromycin B. Further differences were observed in K(+)- and low pH-dependent growth phenotypes. Although CHX17 did not alter cytoplasmic or vacuolar pH in yeast, CHX20 elicited acidification and alkalization of the cytosol and vacuole, respectively. Using heterologous expression in Escherichia coli strains lacking K(+) uptake systems, we provide evidence for K(+) ((86)Rb) transport mediated by CHX17 and CHX20. Finally, we show that CHX17 and CHX20 affected protein sorting as measured by carboxypeptidase Y secretion in yeast mutants grown at alkaline pH. In plant cells, CHX20-RFP co-localized with an endoplasmic reticulum marker, whereas RFP-tagged CHX17-CHX19 co-localized with prevacuolar compartment and endosome markers. Together, these results suggest that in response to environmental cues, multiple CHX transporters differentially modulate K(+) and pH homeostasis of distinct intracellular compartments, which alter membrane trafficking events likely to be critical for adaptation and survival.     

Intercellular colonization and growth promoting effects of Methylobacterium sp. with plant-growth regulators on rice (Oryza sativa L. Cv CO-43)

The Methylobacterium sp. strain NPFM-SB3, isolated from Sesbania rostrata stem nodules possessed nitrogenase activity and nodA genes. Pure culture of NPFM-SB3 strain produced indole-3-acetic acid, cytokinins and on inoculation to rice plants resulted in numerous lateral roots. Inoculation of synthetic auxins 2,4-dichlorophenoxy acetic acid, naphthalene acetic acid or flavonoids naringenin and dihydroxy-4-methoxyisoflavone individually or to bacterial inoculated rice seedlings improved the plant growth and lateral root formation under hydroponic condition. The formation of nodule-like structure and nitrogenase activity which is purely auxin dependent was observed in 2,4-dichlorophenoxy acetic acid treatments to Methylobacterium sp. NPFM-SB3 inoculated rice plants. The rhizobia entered through fissures formed due to lateral root emergence and spread intercellularly in the nodular structures concluded that the effect of 2,4-dichlorophenoxy acetic acid treatment for rice seedlings grown under gnotobiotic conditions is to create a niche in which these bacteria can grow.     

Immobilization of beneficial microbe Methylobacterium aminovorans in electrospun nanofibre as potential seed coatings for improving germination and growth of groundnut Arachis hypogaea

Plant Growth Regulation - Seed inoculation with microbial cells is one of the potential invigouration techniques for enhancing the emergence and growth of plants. Herein, we approached a new...     

Inhibitory role of Ser-425 of the alpha1 2.2 subunit in the enhancement of Cav 2.2 currents by phorbol-12-myristate, 13-acetate

Voltage-gated calcium channels (Ca(v)) 2.2 currents are potentiated by phorbol-12-myristate, 13-acetate (PMA), whereas Ca(v) 2.3 currents are increased by both PMA and acetyl-beta-methylcholine (MCh). MCh-selective sites were identified in the alpha(1) 2.3 subunit, whereas the identified PMA sites responded to both PMA and MCh (Kamatchi, G. L., Franke, R., Lynch, C., III, and Sando, J. J. (2004) J. Biol. Chem. 279, 4102-4109; Fang, H., Franke, R., Patanavanich, S., Lalvani, A., Powell, N. K., Sando, J. J., and Kamatchi, G. L. (2005) J. Biol. Chem. 280, 23559-23565). The hypothesis that PMA sites in the alpha(1) 2.2 subunit are homologous to the PMA-responsive sites in alpha(1) 2.3 subunit was tested with Ser/Thr --> Ala mutations in the alpha(1) 2.2 subunit. WT alpha(1) 2.2 or mutants were expressed in Xenopus oocytes in combination with beta1b and alpha2/delta subunits. Inward current (I(Ba)) was recorded using Ba(2+) as the charge carrier. T422A, S1757A, S2108A, or S2132A decreased the PMA response. In contrast, S425A increased the response to PMA, and thus, it was considered an inhibitory site. Replacement of each of the identified stimulatory Ser/Thr sites with Asp increased the basal current and decreased the PMA-induced enhancement, consistent with regulation by phosphorylation at these sites. Multiple mutant combinations showed (i) greater inhibition than that caused by the single Ala mutations; (ii) that enhancement observed when Thr-422 and Ser-2108 are available may be inhibited by the presence of Ser-425; and (iii) that the combination of Thr-422, Ser-2108, and either Ser-1757 or Ser-2132 can provide a greater response to PMA when Ser-425 is replaced with Ala. The homologous sites in alpha(1) 2.2 and alpha(1) 2.3 subunits seem to be functionally different. The existence of an inhibitory phosphorylation site in the I-II linker seems to be unique to the alpha(1) 2.2 subunit.     

Exogenous NAD Blocks Cardiac Hypertrophic Response via Activation of the SIRT3-LKB1-AMP-activated Kinase Pathway

Since the discovery of NAD-dependent deacetylases, sirtuins, it has been recognized that maintaining intracellular levels of NAD is crucial for the management of stress response of cells. Here we show that agonist-induced cardiac hypertrophy is associated with loss of intracellular levels of NAD, but not exercise-induced physiologic hypertrophy. Exogenous addition of NAD was capable of maintaining intracellular levels of NAD and blocking the agonist-induced cardiac hypertrophic response in vitro as well as in vivo. NAD treatment blocked the activation of pro-hypertrophic Akt1 signaling, and augmented the activity of anti-hypertrophic LKB1-AMPK signaling in the heart, which prevented subsequent induction of mTOR-mediated protein synthesis. By using gene knock-out and transgenic mouse models of SIRT3 and SIRT1, we showed that the anti-hypertrophic effects of exogenous NAD are mediated through activation of SIRT3, but not SIRT1. SIRT3 deacetylates and activates LKB1, thus augmenting the activity of the LKB1-AMPK pathway. These results reveal a novel role of NAD as an inhibitor of cardiac hypertrophic signaling, and suggest that prevention of NAD depletion may be critical in the treatment of cardiac hypertrophy and heart failure.     

Batch kinetic studies on growth of salt tolerant Pseudomonas aeruginosa secreting protease in a biocalorimeter

Biocalorimetry has proved to be an efficient tool for studying the energetics involved in several biochemical reactions. In this study, biocalorimetry was employed to simultaneously analyze biokinetics and bioenergetics involved during cultivation of a salt tolerant Pseudomonas aeruginosa for the production of alkaline protease. Batch experiments were performed in a bench scale biocalorimeter for alkaline protease production by P. aeruginosa using optimized process conditions. Tessier’s double substrate growth model was found to provide a good fit for the growth of P. aeruginosa in the biocalorimeter, and the biokinetic parameters were estimated. The heat flow profile resulting from metabolic activity of P. aeruginosa was shown to accurately depict both the kinetics of cell growth and protease production. Biokinetic and bioenergetic analysis on the growth of P. aeruginosa revealed that peptone is preferentially used as the substrate for its intracellular activities and glycerol acts as an energy source for its growth metabolism.