Activity-Profiling of Vacuolar Processing Enzymes and the Proteasome during Plant-Pathogen Interactions

Programmed cell death (PCD) is an interesting natural phenomenon, common to many organisms. PCD has been extensively studied during animal apoptosis and several regulators have been identified. Cysteine proteases called caspases, and the proteasome were found to be main players in PCD in animals. In plants, PCD is regulated by vacuolar processing enzymes (VPEs) and the proteasome. Both proteolytic machineries exhibit caspase-like activities. In this work, the activity of VPEs and the proteasome were characterized using activity-based protein profiling (ABPP). ABPP involves fluorescent or biotinylated probes that react with the catalytic residue of proteases in an activity-dependent manner. Specific probes that target γVPE, the most abundant VPE in vegetative tissue, were selected from screen with legumain probes. Further characterization of γVPE activity revealed an unexpected, post-transcriptional up-regulation of γVPE activity during compatible, but not during incompatible interactions of Arabidopsis with Hyaloperonospora arabidopsidis (Hpa). Sporulation of Hpa was reduced in the absence of VPEs indicating that VPEs promote pathogen fitness. These findings introduce a new tool to study VPEs and reveal a new role of VPEs during compatible interactions. New, selective probes that target the plant proteasome are also introduced in this thesis. The proteasome is a multi-subunit proteolytic complex containing three subunits with different catalytic activities: β1, β2 and β5. ABPP was applied to further characterize the inhibition of the plant proteasome by Syringolin A (SylA), a non-ribosomal cyclic peptide produced by the bacterial pathogen Pseudomonas syringae pv. syringae. This work shows that SylA preferentially targets β2 and β5 of the plant proteasome. Structure-activity analysis revealed that dipeptide tail of SylA contributes to β2 specificity and identified a nonreactive SylA derivative. The selectivity of SylA for the catalytic subunits is discussed and the subunit selectivity is explained by crystallographic data. Importantly, it was discovered that SylA production promotes colonization of distant tissue by Pseudomonas syringae pv. syringae. SylA was found to suppress both effector-triggered immunity and salicylic acid-dependent acquired resistance. Distant colonization is a new phenomenon, common to other P. syringae strains, and undetected by classical pathogen assays

Globalization, Adjustment, and Employment Drivers

This study is a comparative analysis of the relative performance of two key industries in the Philippines during the period when the country liberalized trade. These industries are (1) the textile and garments industry and (2) the information and communications technology (ICT)-based industries consisting of the electronics industry and the business process outsourcing (BPO) services sector

Leaf Anatomy and Ultrastructure of Poa Ligularis After Defoliation and Water Stress

The objective of this study was to determine the effect of defoliation and water stress on leaf anatomy and the mesophyll cell ultrastructure of Poa ligularis. Anatomical differences were detected mainly at epidermal level. Under water stress, leaf roughness was enhanced since the epidermal-cell surface contours became conspicuous. Under defoliation the microscopic roughness decreased as a result of fewer epicuticular wax crystals being formed. Defoliation produced an enhancement of the interlamellar spaces in the irrigated plantís chloroplast. Under no defoliation conditions, chloroplast structure was not affected by water stress. When subjected to water stress, lightly defoliated plants presented chloroplasts with a bellowed outer membrane, irregular thylacoid distribution and the disorganization of peripheral grana. Severely defoliated plants showed disorganized internal chloroplast membranes and even the disappearance of the grana. No breakdown or disappearance of chloroplast external membranes was detected under the imposed growing conditions, suggesting that no irreversible changes were induced

Citrullus lanatus subsp. lanatus, naturalizada en la Argentina

The presence of Citrullus lanatus (Thunb.) Matsum. & Nakai subsp. lanatus naturalized in Argentina is recorded for the first time, and its present distribution in the country is precised.Se cita por primera vez la presencia de Citrullus lana tus (Thunb.) Matsum. & Nakai subsp. lanatus como naturalizada en la Argentina y se precisa su actual distribución en el país

Long-term residue removal under tillage decreases amoA-nitrifiers and stimulates nirS-denitrifier groups in the soil

No-till in continuous corn (Zea mays L.) production helps to keep an important volume of residues on the soil surface, creating management challenges that could be alleviated by residue removal for bioenergy or animal use. Crop residues, however, are essential to stimulate microbial nutrient cycling in agroecosystems. Thus, both residue removal and tillage options need to be fully evaluated for their impacts on ecosystem services related to soil health, including microbial N cycling. We explored the main steps of the microbial N cycle in relation to soil properties by using targeted gene abundance as a proxy following over a decade of residue removal in continuous corn systems either under no-till or chisel tillage. We used real-time quantitative polymerase chain reaction (qPCR) for the quantification of phylogenetic groups and functional gene screening of the soil microbial communities, including genes encoding critical enzymes of the microbial N cycle: nifH (N2 fixation), amoA (nitrification – ammonia oxidation), nirK and nirS (denitrification – nitrite reduction), and nosZ (denitrification – nitrous oxide reduction). Our results showed that long-term residue removal and tillage decreased soil organic matter (SOM), water aggregate stability (WAS), and the relative abundance (RA) of ammonia-oxidizing bacteria (AOB) carrying nitrifying amoA genes. Denitrifiers carrying nirS genes decreased under no-till as crop residue was removed. In addition, our results evidenced strong correlations among soil properties and phylogenetic groups of bacteria, archaea, and fungi. Overall, this study demonstrated limited but definite impacts of residue management and tillage on the soil environment, which could be exacerbated under less resilient conditions.Fil: Kim, N.. University of Illinois; Estados UnidosFil: Riggins, C. W.. University of Illinois; Estados UnidosFil: Rodríguez Zas, S.. University of Illinois; Estados UnidosFil: Zabaloy, Maria Celina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Villamil, Maria Bonita. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. University of Illinois; Estados Unido

Transcription activation depends on the length of the RNA polymerase II C‐terminal domain

Eukaryotic RNA polymerase II (Pol II) contains a tail‐like, intrinsically disordered carboxy‐terminal domain (CTD) comprised of heptad‐repeats, that functions in coordination of the transcription cycle and in coupling transcription to co‐transcriptional processes. The CTD repeat number varies between species and generally increases with genome size, but the reasons for this are unclear. Here, we show that shortening the CTD in human cells to half of its length does not generally change pre‐mRNA synthesis or processing in cells. However, CTD shortening decreases the duration of promoter‐proximal Pol II pausing, alters transcription of putative enhancer elements, and delays transcription activation after stimulation of the MAP kinase pathway. We suggest that a long CTD is required for efficient enhancer‐dependent recruitment of Pol II to target genes for their rapid activation

Acidification in corn monocultures favor fungi, ammonia oxidizing bacteria, and nirK-denitrifier groups

Agricultural practices of no-till and crop rotations are critical to counteract the detrimental effects of monocultures and tillage operations on ecosystem services related to soil health such as microbial N cycling. The present study explored the main steps of the microbial N cycle, using targeted gene abundance as a proxy, and concerning soil properties, following 19 and 20 years of crop monocultures and rotations of corn (Zea mays L.), and soybean [Glycine max (L.) Merr.], either under no-till or chisel tillage. Real-time quantitative polymerase chain reaction (qPCR) was implemented to estimate phylogenetic groups and functional genes related to the microbial N cycle: nifH (N2 fixation), amoA (nitrification) and nirK, nirS, and nosZ (denitrification). Our results indicate that long-term crop rotation and tillage decisions affect soil health as it relates to soil properties and microbial parameters. No-till management increased soil organic matter (SOM), decreased soil pH, and increased copy numbers of AOB (ammonia oxidizing bacteria). Crop rotations with more corn increased SOM, reduced soil pH, reduced AOA (ammonia oxidizing archaea) copy numbers, and increased AOB and fungal ITS copy numbers. NirK denitrifier groups were also enhanced under continuous corn. Altogether, the more corn years included in a crop rotation multiplies the amount of N needed to sustain yield levels, thereby intensifying the N cycle in these systems, potentially leading to acidification, enhanced bacterial nitrification, and creating an environment primed for N losses and increased N2O emissions.Fil: Behnke, G. D.. University of Illinois; Estados UnidosFil: Zabaloy, Maria Celina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Riggins, C. W.. University of Illinois; Estados UnidosFil: Rodríguez-Zas, S.. University of Illinois; Estados UnidosFil: Huang, L.. University of Illinois; Estados UnidosFil: Villamil, Maria Bonita. University of Illinois; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin