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Systemic acquired resistance (SAR) is an enhanced defence response triggered when plants detect a pathogen. The response is extended to uninfected organs to protect against future attack. NPR1 is a nuclear leucine-rich repeat protein with a key role in SAR. It binds specifically to salicylic acid, and acts as a transcriptional coregulator of SAR activators and an inhibitor of transcriptional repressors. The proteins encoded by Suppressor of NPR1, Constitutive (SNC1) and Suppressor of NPR1, Inducible (SNI1) interact with NPR1 to regulate the expression of pathogenesis-related genes. The Arabidopsis thaliana (L.) Heynh. snc1 mutant exhibits a constitutive resistance response, but in the sni1 mutant, the SNI1 protein is rendered incapable of suppressing pathogen resistance genes. To study the influence of SNC1andSNI1onresistancetothesoybeancystnematode(Heteroderaglycines), soybean(Glycinemax(L.) Merr.) roots were separately transformed with four constructs designed to: (i) overexpress GmSNC1, the soybean orthologue of AtSNC1; (ii) overexpress AtSNI1; (iii) silence GmSNC1 and (iv) silence GmSNI1. A significant reduction of the female nematode population was observed in Treatments (i) and (iv). The expression of SAR marker genes was analysed in these treatments. The unusual pattern of expression of pathogen resistance genes shows there are differences in the effect resistance genes have on soybean and A. thaliana. Although NPR1 is involved in the cross-talk between the salicylic acid, jasmonic acid and ethylene pathways, understanding the nematode resistance mechanism in plants is still imprecise. These results provide further insights into the soybean defence response. [ABSTRACT FROM AUTHOR]

Abstract: Glycine max is one of the most important cash-crops in the US. Major losses in soybean production are reported annually due to the attack of the soybean cyst nematode (Heterodera glycines). Since chemical control is neither environmental nor economically viable, efforts have been focused on enhancing the plants defense system. Plants have developed mechanisms to identify and react to pathogen attack. Basal defenses are activated by resistance (R) proteins. The Arabidopsis NON-RACE-SPECIFIC DISEASE RESISTANCE 1, NDR1 protein shows some sequence similarity to the tobacco HAIRPIN INDUCED GENE 1 (HIN1), is localized to the plasma membrane, and usually interacts with CC-NB-LRR R proteins to mediate defense signaling. Forty five NDR1/HIN1-LIKE (NHL) genes have been found in Arabidopsis. Four of them were overexpressed in soybean roots to determine if they could confer resistance to H. glycines. AtNHL1 and AtNHL8 significantly decreased the number of mature females to 50 and 46% of the number found in control roots. Relative expression analysis showed they induced the expression of marker genes for jasmonic acid (PR3 and OSM, encoding chitinase B and an osmotin, respectively) and ethylene (EBF, ERF1, and ERS2, encoding the EIN3-binding F box protein, the ethylene response factor 1, and the ethylene response sensor 2, respectively). NHL1 is most similar to NDR1, and NHL8 is an E3 ubiquitin ligase, Ariadne ring zinc finger protein. Our observations confirm the role of NHL1 and NHL8 in the plant defense mechanism against pathogens observed in Arabidopsis, by conferring resistance to SCN in soybean. [Copyright &y& Elsevier]

Abstract: A strain of sulfate-reducing bacteria, designated strain ‘DBM’, was isolated from sediments of a mining area. Phylogenetic analysis of the 16S rRNA gene sequence of the isolate revealed that it was related to members of the genus Citrobacter, with C. AzoR-4, C. freundii, C. braakii and C. werkmanii being the most closely related species (sequence similarity up to 98%). Few studies have been done on sulfate reduction ability in Citrobacter. Electron microscopy studies showed that the morphology of the strain DBM was rod-shaped. Strain DBM reduced 10mM of sulfate completely to sulfide within 7d, and it recovered its sulfate reduction ability after 7d of aerobic growth. Furthermore, strain DBM effectively precipitated 0.40mM copper during its growth. Elemental composition of the resulting microbial precipitate was studied using electro-dispersive X-ray spectroscopy, and it was found that the ratio of S:Cu was 1.07. The result was consistent with the formation of copper sulfide. Heavy metal precipitation by Citrobacter sp. strain DBM was a phenomenon that may be useful in the bioremediation of acid mine drainage. [Copyright &y& Elsevier]

The copolymer poly(fluorene-co-thiophene) (PFT) has strong absorption in the visible light region. In this paper, PFTs with four different thiophene contents were evaluated for their suitability as photosensitizers of TiO2. All four of the PFTs were capable of being excited by light with wavelengths above 455 nm, and all had reductive potentials more negative than the conduction band potential of TiO2. Consequently, it was deemed that transfer of electrons from the excited PFTs to the conduction band of TiO2 was thermodynamically possible. PFTs with higher thiophene content had more electron transitions in the excited state, resulting in increased photocatalytic activity of PFT-sensitized TiO2. The method used to prepare the combined PFT/TiO2 photocatalyst affected its photocatalytic activity. Best results in this study were achieved by dropwise addition of a tetrahydrofuran solution of PFT to a stirred TiO2/ethanol suspension. [ABSTRACT FROM AUTHOR]

Contigs with the highest sequence similarity (73%) to Apricot pseudo-chlorotic leaf spot virus (genus Trichovirus, family Betaflexiviridae) were identified by high-throughput sequencing from a symptomless sweet cherry accession. The complete genome sequence of this new virus is 7460 nucleotides, excluding the 3' poly(A) tail. Its genome organization is very similar to several trichoviruses infecting fruit trees, with three open reading frames encoding putative replicase, movement protein and coat protein (CP). The virus shares amino acid sequence identities of 60-73% at replicase and 53-76% at CP with other trichoviruses. Phylogenetic analyses group it and other trichoviruses in a cluster. These results support that this virus, which is tentatively named cherry latent virus 1, should be considered a new member in the genus Trichovirus.

During pathogen attack, the host plant induces genes to ward off the pathogen while the pathogen often produces effector proteins to increase susceptibility of the host. Gene expression studies of syncytia formed in soybean root by soybean cyst nematode (Heterodera glycines) identified many genes altered in expression in resistant and susceptible roots. However, it is difficult to assess the role and impact of these genes on resistance using gene expression patterns alone. We selected 100 soybean genes from published microarray studies and individually overexpressed them in soybean roots to determine their impact on cyst nematode development. Nine genes reduced the number of mature females by more than 50 % when overexpressed, including genes encoding ascorbate peroxidase, β-1,4-endoglucanase, short chain dehydrogenase, lipase, DREPP membrane protein, calmodulin, and three proteins of unknown function. One gene encoding a serine hydroxymethyltransferase decreased the number of mature cyst nematode females by 45 % and is located at the Rhg4 locus. Four genes increased the number of mature cyst nematode females by more than 200 %, while thirteen others increased the number of mature cyst nematode females by more than 150 %. Our data support a role for auxin and ethylene in susceptibility of soybean to cyst nematodes. These studies highlight the contrasting gene sets induced by host and nematode during infection and provide new insights into the interactions between host and pathogen at the molecular level. Overexpression of some of these genes result in a greater decrease in the number of cysts formed than recognized soybean cyst nematode resistance loci.

Two strategies of phytoextraction have been shown to have promise for practical soil remediation: domestication of natural hyperaccumulators and bioengineering plants with the genes that allow natural hyperaccumulators to achieve useful phytoextraction. Because different elements have different value, some can be phytomined for profit and others can be phytoremediated at lower cost than soil removal and replacement. Ni phytoextraction from contaminated or mineralized soils offers economic return greater than producing most crops, especially when considering the low fertility or phytotoxicity of Ni rich soils. Only soils that require remediation based on risk assessment will comprise the market for phytoremediation. Improved risk assessment has indicated that most Zn + Cd contaminated soils will not require Cd phytoextraction because the Zn limits practical risk from soil Cd. But rice and tobacco, and foods grown on soils with Cd contamination without corresponding 100-fold greater Zn contamination, allow Cd to readily enter food plants and diets. Clear evidence of human renal tubular dysfunction from soil Cd has only been obtained for subsistence rice farm families in Asia. Because of historic metal mining and smelting, Zn + Cd contaminated rice soils have been found in Japan, China, Korea, Vietnam and Thailand. Phytoextraction using southern France populations of Thlaspi caerulescens appears to be the only practical method to alleviate Cd risk without soil removal and replacement. The southern France plants accumulate 10-20-fold higher Cd in shoots than most T. caerulescens populations such as those from Belgium and the UK. Addition of fertilizers to maximize yield does not reduce Cd concentration in shoots; and soil management promotes annual Cd removal. The value of Cd in the plants is low, so the remediation service must pay the costs of Cd phytoextraction plus profits to the parties who conduct phytoextraction. Some other plants have been studied for Cd phytoextraction, but annual removals are much lower than the best T. caerulescens. Improved cultivars with higher yields and retaining this remarkable Cd phytoextraction potential are being bred using normal plant breeding techniques.