Ectopic phytocystatin expression leads to enhanced drought stress tolerance in soybean (Glycine max) and Arabidopsis thaliana through effects on strigolactone pathways and can also result in improved seed traits

Ectopic cystatin expression has long been used in plant pest management, but the cysteine protease, targets of these inhibitors, might also have important functions in the control of plant lifespan and stress tolerance that remain poorly characterized. We therefore characterized the effects of expression of the rice cystatin, oryzacystatin‐I (OCI), on the growth, development and stress tolerance of crop (soybean) and model (Arabidopsis thaliana) plants. Ectopic OCI expression in soybean enhanced shoot branching and leaf chlorophyll accumulation at later stages of vegetative development and enhanced seed protein contents and decreased the abundance of mRNAs encoding strigolactone synthesis enzymes. The OCI‐expressing A. thaliana showed a slow‐growth phenotype, with increased leaf numbers and enhanced shoot branching at flowering. The OCI‐dependent inhibition of cysteine proteases enhanced drought tolerance in soybean and A. thaliana, photosynthetic CO₂ assimilation being much less sensitive to drought‐induced inhibition in the OCI‐expressing soybean lines. Ectopic OCI expression or treatment with the cysteine protease inhibitor E64 increased lateral root densities in A. thaliana. E64 treatment also increased lateral root densities in the max2‐1 mutants that are defective in strigolactone signalling, but not in the max3‐9 mutants that are defective in strigolactone synthesis. Taken together, these data provide evidence that OCI‐inhibited cysteine proteases participate in the control of growth and stress tolerance through effects on strigolactones. We conclude that cysteine proteases are important targets for manipulation of plant growth, development and stress tolerance, and also seed quality traits.     

In vivo interaction of trivalent chromium with yeast plasma membrane, as revealed by EPR spectroscopy

The in vivo effects of CrCl(3) on an ergosterol-producing 33 erg(+) strain of the eukaryotic yeast Candida albicans, and on its ergosterol-deficient erg(-)2 mutant, were studied by using electron paramagnetic resonance spectroscopy. A 5-doxylstearic acid spin probe was applied to label the membranes. The absence of ergosterol, an increased accumulation of Delta(8) sterols, a decreased fatty acid chainlength and a lower proportion of unsaturated fatty acids of the erg(-)2 mutant resulted in a higher membrane rigidity and an increased sensitivity to Cr(III) than those of the parental 33 erg(+) strain. Cr(III) significantly increased the fluidity of the spin labelled membranes, this being more pronounced for the erg(-)2 mutant. The break in the slopes measured for the erg(-)2 mutant was decreased (DeltaAT approximately 4 degrees C) from 17 to 13 degrees C. Cr(III) treatment for 10 h caused a loss of metabolites adsorbing at 260 nm: this loss was 40% for 33 erg(+) and 60% for erg(-)2. This decriptification process might be the main cause of growth inhibition and cell killing by the impermeable Cr(III) ions.     

Identification of a novel galactosyl transferase involved in biosynthesis of the mycobacterial cell wall

The possibility of the Rv3782 protein of Mycobacterium tuberculosis being a putative galactosyl transferase (GalTr) implicated in galactan synthesis arose from its similarity to the known GalTr Rv3808c, its classification as a nucleotide sugar-requiring inverting glycosyltransferase (GT-2 family), and its location within the "possible arabinogalactan biosynthetic gene cluster" of M. tuberculosis. In order to study the function of the enzyme, active membrane and cell wall fractions from Mycobacterium smegmatis containing the overexpressed Rv3782 protein were incubated with endogenous decaprenyldiphosphoryl-N-acetylglucosaminyl-rhamnose (C(50)-P-P-GlcNAc-Rha) as the primary substrate for galactan synthesis and UDP-[(14)C]galactopyranose as the immediate precursor of UDP-[(14)C]galactofuranose, the ultimate source of all of the galactofuranose (Galf) units of galactan. Obvious increased and selective synthesis of C(50)-P-P-GlcNAc-Rha-Galf-Galf, the earliest product in the pathway leading to the fully polymerized galactan, was observed, suggesting that Rv3782 encodes a GalTr involved in the first stages of galactan synthesis. Time course experiments pointed to a possible bifunctional enzyme responsible for the initial synthesis of C(50)-P-P-GlcNAc-Rha-Galf, followed by immediate conversion to C(50)-P-P-GlcNAc-Rha-Galf-Galf. Thus, Rv3782 appears to be the initiator of galactan synthesis, while Rv3808c continues with the subsequent polymerization events.     

Nitrogenous Nutrients Promote the Growth and Toxicity of Dinophysis acuminata during Estuarine Bloom Events

Diarrhetic Shellfish Poisoning (DSP) is a globally significant human health syndrome most commonly caused by dinoflagellates within the genus Dinophysis. While blooms of harmful algae have frequently been linked to excessive nutrient loading, Dinophysis is a mixotrophic alga whose growth is typically associated with prey availability. Consequently, field studies of Dinophysis and nutrients have been rare. Here, the temporal dynamics of Dinophysis acuminata blooms, DSP toxins, and nutrients (nitrate, ammonium, phosphate, silicate, organic compounds) were examined over four years within two New York estuaries (Meetinghouse Creek and Northport Bay). Further, changes in the abundance and toxicity of D. acuminata were assessed during a series of nutrient amendment experiments performed over a three year period. During the study, Dinophysis acuminata blooms exceeding one million cells L-1 were observed in both estuaries. Highly significant (p<0.001) forward stepwise multivariate regression models of ecosystem observations demonstrated that D. acuminata abundances were positively dependent on multiple environmental parameters including ammonium (p = 0.007) while cellular toxin content was positively dependent on ammonium (p = 0.002) but negatively dependent on nitrate (p<0.001). Nitrogen- (N) and phosphorus- (P) containing inorganic and organic nutrients significantly enhanced D. acuminata densities in nearly all (13 of 14) experiments performed. Ammonium significantly increased cell densities in 10 of 11 experiments, while glutamine significantly enhanced cellular DSP content in 4 of 5 experiments examining this compound. Nutrients may have directly or indirectly enhanced D. acuminata abundances as densities of this mixotroph during experiments were significantly correlated with multiple members of the planktonic community (phytoflagellates and Mesodinium). Collectively, this study demonstrates that nutrient loading and more specifically N-loading promotes the growth and toxicity of D. acuminata populations in coastal zones.     

Dynamics of plasmodesmal connectivity in successive interfaces of the cambial zone

Frequency, density and branching of plasmodesmata were counted in successive tangential and transverse walls in the cambial zone of tomato stems in order to examine development of the plasmodesmal network in a chronological order. Coincident with progress of cell development, plasmodesmal connectivity increased, both at the xylem- and phloem-side. In transverse walls, the number of secondary plasmodesmata enhanced considerably. The same held for tangential walls, with a superimposed plasmodesmal doubling during the first phase of phloem development. This plasmodesmal doubling was interpreted to result from the deposition of wall material between branched plasmodesmal strands. Structural plasmodesmal development was correlated with production of hydroxyl radicals which control local cell wall alterations. Successive phases of plasmodesmal deployment and modification were distinguished which may coincide with differential functional capacities as documented by intracellular injection of fluorochromes. Diffusion-driven symplasmic transport appeared to be transiently interrupted during cell maturation.     

Generation,annotation, and analysis of ESTs from four different <Emphasis Type="Italic">Trichoderma</Emphasis> strains grown under conditions related to biocontrol

The functional genomics project “TrichoEST” was developed focused on different taxonomic groups of Trichoderma with biocontrol potential. Four cDNA libraries were constructed, using similar growth conditions, from four different Trichoderma strains: Trichoderma longibrachiatum T52, Trichoderma asperellum T53, Trichoderma virens T59, and Trichoderma sp. T78. In this study, we present the analysis of the 8,160 expressed sequence tags (ESTs) generated. Each EST library was independently assembled and 1,000–1,300 unique sequences were identified in each strain. First, we queried our collection of ESTs against the NCBI nonredundant database using the BLASTX algorithm. Moreover, using the Gene Ontology hierarchy, we performed the annotation of 40.9% of the unique sequences. Later, based on the EST abundance, we examined the highly expressed genes in the four strains. A hydrophobin was found as the gene expressed at the highest level in two of the strains, but we also found that other unique sequences similar to the HEX1, QID3, and NMT1 proteins were highly represented in at least two of the Trichoderma strains. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Alternative Conservation Paradigms and Ecological Knowledge of Small-Scale Artisanal Fishers in a Changing Marine Scenario in Argentina

Human Ecology - We studied conservation paradigms of small-scale artisanal fishers and other actors involved in the conservation of the Bahía Blanca Estuary (BBE)—a Southwestern Atlantic...