Enhancing rice resistance to fungal pathogens by transformation with cell wall degrading enzyme genes from Trichoderma atroviride

Three genes encoding for fungal cell wall degrading enzymes (CWDEs), ech42, nag70 and gluc78 from the biocontrol fungus Trichoderma atroviride were inserted into the binary vector pCAMBIA1305.2 singly and in all possible combinations and transformed to rice plants. More than 1800 independently regenerated plantlets in seven different populations (for each of the three genes and each of the four gene combinations) were obtained. The ech42 gene encoding for an endochitinase increased resistance to sheath blight caused by Rhizoctonia solani, while the exochitinase-encoding gene, nag70, had lesser effect. The expression level of endochitinase but exochitinase was correlated with disease resistance. Nevertheless, exochitinase enhanced the effect of endochitinase on disease resistance when the two genes co-expressed in transgenics. Resistance to Magnaporthe grisea was found in all kinds of regenerated plants including that with single gluc78. A few lines expressing either ech42 or nag70 gene were immune to the disease. Transgenic plants are being tested to further evaluate disease resistance at field level. This is the first report of multiple of expression of genes encoding CWDEs from Trichoderma atroviride that result in resistance to blast and sheath blight in rice.     

MicroRNA-responsive 'sensor' transgenes uncover Hox-like and other developmentally regulated patterns of vertebrate microRNA expression

MicroRNAs (miRNAs) are a class of short ( approximately 22-nt) noncoding RNA molecules that downregulate expression of their mRNA targets. Since their discovery as regulators of developmental timing in Caenorhabditis elegans, hundreds of miRNAs have been identified in both animals and plants. Here, we report a technique for visualizing detailed miRNA expression patterns in mouse embryos. We elucidate the tissue-specific expression of several miRNAs during embryogenesis, including two encoded by genes embedded in homeobox (Hox) clusters, miR-10a and miR-196a. These two miRNAs are expressed in patterns that are markedly reminiscent of those of Hox genes. Furthermore, miR-196a negatively regulates Hoxb8, indicating that its restricted expression pattern probably reflects a role in the patterning function of the Hox complex.     

A systematic RNAi screen identifies a critical role for mitochondria in C. elegans longevity

We report a systematic RNA interference (RNAi) screen of 5,690 Caenorhabditis elegans genes for gene inactivations that increase lifespan. We found that genes important for mitochondrial function stand out as a principal group of genes affecting C. elegans lifespan. A classical genetic screen identified a mutation in the mitochondrial leucyl-tRNA synthetase gene (lrs-2) that impaired mitochondrial function and was associated with longer-lifespan. The long-lived worms with impaired mitochondria had lower ATP content and oxygen consumption, but differential responses to free-radical and other stresses. These data suggest that the longer lifespan of C. elegans with compromised mitochrondria cannot simply be assigned to lower free radical production and suggest a more complex coupling of metabolism and longevity.     

Evolving concepts of rheumatoid arthritis

Rheumatoid arthritis is the most common inflammatory arthritis and is a major cause of disability. It existed in early Native American populations several thousand years ago but might not have appeared in Europe until the 17th century. Early theories on the pathogenesis of rheumatoid arthritis focused on autoantibodies and immune complexes. T-cell-mediated antigen-specific responses, T-cell-independent cytokine networks, and aggressive tumour-like behaviour of rheumatoid synovium have also been implicated. More recently, the contribution of autoantibodies has returned to the forefront. Based on the pathogenic mechanisms, specific therapeutic interventions can be designed to suppress synovial inflammation and joint destruction in rheumatoid arthritis.     

Genome sequence of Bacillus cereus and comparative analysis with Bacillus anthracis

Bacillus cereus is an opportunistic pathogen causing food poisoning manifested by diarrhoeal or emetic syndromes. It is closely related to the animal and human pathogen Bacillus anthracis and the insect pathogen Bacillus thuringiensis, the former being used as a biological weapon and the latter as a pesticide. B. anthracis and B. thuringiensis are readily distinguished from B. cereus by the presence of plasmid-borne specific toxins (B. anthracis and B. thuringiensis) and capsule (B. anthracis). But phylogenetic studies based on the analysis of chromosomal genes bring controversial results, and it is unclear whether B. cereus, B. anthracis and B. thuringiensis are varieties of the same species or different species. Here we report the sequencing and analysis of the type strain B. cereus ATCC 14579. The complete genome sequence of B. cereus ATCC 14579 together with the gapped genome of B. anthracis A2012 enables us to perform comparative analysis, and hence to identify the genes that are conserved between B. cereus and B. anthracis, and the genes that are unique for each species. We use the former to clarify the phylogeny of the cereus group, and the latter to determine plasmid-independent species-specific markers.     

Assessing the redundancy of MADS-box genes during carpel and ovule development

Carpels are essential for sexual plant reproduction because they house the ovules and subsequently develop into fruits that protect, nourish and ultimately disperse the seeds. The AGAMOUS (AG) gene is necessary for plant sexual reproduction because stamens and carpels are absent from ag mutant flowers. However, the fact that sepals are converted into carpelloid organs in certain mutant backgrounds even in the absence of AG activity indicates that an AG-independent carpel-development pathway exists. AG is a member of a monophyletic clade of MADS-box genes that includes SHATTERPROOF1 (SHP1), SHP2 and SEEDSTICK (STK), indicating that these four genes might share partly redundant activities. Here we show that the SHP genes are responsible for AG-independent carpel development. We also show that the STK gene is required for normal development of the funiculus, an umbilical-cord-like structure that connects the developing seed to the fruit, and for dispersal of the seeds when the fruit matures. We further show that all four members of the AG clade are required for specifying the identity of ovules, the landmark invention during the course of vascular plant evolution that enabled seed plants to become the most successful group of land plants.     

Co-integration,error correction and improved medium-term regional VAR forecasting

This study investigates possible improvements in medium-term VAR forecasting of state retail sales and personal income when the two series are co-integrated and represent an error-correction system. For each of North Carolina and New York, three regional vector autoregression (VAR) models are specified; an unrestricted two-equation model consisting of the two state variables, a five-equation unrestricted model with three national variables added and a Bayesian (BVAR) version of the second model. For each state, the co-integration and error-correction relationship of the two state variables is verified and an error-correction version of each model specified. Twelve successive ex ante five-year forecasts are then generated for each of the state models. The results show that including an error-correction mechanism when statistically significant improves medium-term forecasting accuracy in every case.     

Systematic analysis of genes required for synapse structure and function

Chemical synapses are complex structures that mediate rapid intercellular signalling in the nervous system. Proteomic studies suggest that several hundred proteins will be found at synaptic specializations. Here we describe a systematic screen to identify genes required for the function or development of Caenorhabditis elegans neuromuscular junctions. A total of 185 genes were identified in an RNA interference screen for decreased acetylcholine secretion; 132 of these genes had not previously been implicated in synaptic transmission. Functional profiles for these genes were determined by comparing secretion defects observed after RNA interference under a variety of conditions. Hierarchical clustering identified groups of functionally related genes, including those involved in the synaptic vesicle cycle, neuropeptide signalling and responsiveness to phorbol esters. Twenty-four genes encoded proteins that were localized to presynaptic specializations. Loss-of-function mutations in 12 genes caused defects in presynaptic structure.