Proteomic Analysis of Upland Rice (Oryza sativa L.) Exposed to Intermittent Water Deficit

Rice is the most important crop consumed all over the world. In Brazil, irrigated rice covers 50 % of the rice producing area and is responsible for 75 % of the national production. Upland rice covers most of the remaining area, and is therefore, a very important production system in the country. In the present study, we have used the drought tolerant upland rice variety Três Meses Antigo to investigate the proteomic changes that occur during drought stress. Plants were submitted to drought by the reposition of 50 % of the water lost daily. Twenty days after the beginning of the drought stress period, leaves were harvested and used for protein extraction. The 2D maps obtained from treated and control plants revealed 408 reproducible spots, 44 of which were identified by mass spectrometry, including 15 differential proteins. Several unaltered proteins were also identified (39 spots) and were mainly involved in photosynthesis. Taken together, the results obtained suggest that the tolerant upland rice up-regulates anti-oxidant and energy production related proteins in order to cope with water deficit.     

Comparative proteome analysis of Xanthomonas campestris pv. campestris in the interaction with the susceptible and the resistant cultivars of Brassica oleracea

Black rot of cruciferous plants, caused by Xanthomonas campestris pv. campestris , causes severe losses in agriculture around the world. This disease affects several cultures, including cabbage and broccoli, among others. Proteome studies of this bacterium have been reported; however, most of them were performed using the bacterium grown under culture media conditions. Recently, we have analyzed the proteome of X. campestris pv. campestris during the interaction with the susceptible cultivar of Brassica oleracea and several proteins were identified. The objective of the present study was to analyze the expressed proteins of X. campestris pv. campestris during the interaction with the resistant cultivar of B. oleracea . The bacterium was infiltrated in the leaves of the resistant plant and recovered for protein extraction and two-dimensional electrophoresis. The protein profile was compared with that of the bacterium isolated from the susceptible host and the results obtained revealed a group of proteins exclusive to the resistant interaction. Among the proteins identified in this study were plant and bacterium proteins, some of which were exclusively expressed during the resistant interaction.     

Uridylylation of Herbaspirillum seropedicae GlnB and GlnK proteins is differentially affected by ATP, ADP and 2-oxoglutarate in vitro

PII are signal-transducing proteins that integrate metabolic signals and transmit this information to a large number of proteins. In proteobacteria, PII are modified by GlnD (uridylyltransferase/uridylyl-removing enzyme) in response to the nitrogen status. The uridylylation/deuridylylation cycle of PII is also regulated by carbon and energy signals such as ATP, ADP and 2-oxoglutarate (2-OG). These molecules bind to PII proteins and alter their tridimensional structure/conformation and activity. In this work, we determined the effects of ATP, ADP and 2-OG levels on the in vitro uridylylation of Herbaspirillum seropedicae PII proteins, GlnB and GlnK. Both proteins were uridylylated by GlnD in the presence of ATP or ADP, although the uridylylation levels were higher in the presence of ATP and under high 2-OG levels. Under excess of 2-OG, the GlnB uridylylation level was higher in the presence of ATP than with ADP, while GlnK uridylylation was similar with ATP or ADP. Moreover, in the presence of ADP/ATP molar ratios varying from 10/1 to 1/10, GlnB uridylylation level decreased as ADP concentration increased, whereas GlnK uridylylation remained constant. The results suggest that uridylylation of both GlnB and GlnK responds to 2-OG levels, but only GlnB responds effectively to variation on ADP/ATP ratio.     

The Bacterial signal transduction protein GlnB regulates the committed step in fatty acid biosynthesis by acting as a dissociable regulatory subunit of acetyl‐CoA carboxylase

Biosynthesis of fatty acids is one of the most fundamental biochemical pathways in nature. In bacteria and plant chloroplasts, the committed and rate‐limiting step in fatty acid biosynthesis is catalyzed by a multi‐subunit form of the acetyl‐CoA carboxylase enzyme (ACC). This enzyme carboxylates acetyl‐CoA to produce malonyl‐CoA, which in turn acts as the building block for fatty acid elongation. In Escherichia coli, ACC is comprised of three functional modules: the biotin carboxylase (BC), the biotin carboxyl carrier protein (BCCP) and the carboxyl transferase (CT). Previous data showed that both bacterial and plant BCCP interact with signal transduction proteins belonging to the P_II family. Here we show that the GlnB paralogues of the P_II proteins from E. coli and Azospirillum brasiliense, but not the GlnK paralogues, can specifically form a ternary complex with the BC‐BCCP components of ACC. This interaction results in ACC inhibition by decreasing the enzyme turnover number. Both the BC‐BCCP‐GlnB interaction and ACC inhibition were relieved by 2‐oxoglutarate and by GlnB uridylylation. We propose that the GlnB protein acts as a 2‐oxoglutarate‐sensitive dissociable regulatory subunit of ACC in Bacteria.     

Historical trends in frog populations in New Zealand based on public perceptions

Surveys were distributed to New Zealand land users in 1998 and 2008 to acquire information about New Zealand frogs with the aim of compiling and mapping their distribution and inferred population trends without costly and time-consuming field surveys. The overall frog population trend was reported as declining, with possible causes reported as an increase in agriculture, an increase in the distribution of predatory fish and disease. The resultant maps could be used for four main purposes: 1) to identify regions where Litoria populations are known to occur, which can be eliminated when considering suitable regions for translocation of Leiopelma; 2) to identify growing or stable populations of Litoria species, which may assist future disease surveys, population monitoring and to identify sources of genetic material that may serve as an Ark for declining Australian populations; 3) to highlight populations that are in decline to enable effective targeting of detailed disease studies; and 4) to approximate the stability of amphibian populations in the absence of more accurate, but costly, scientific monitoring.     

Search for novel targets of the PII signal transduction protein in Bacteria identifies the BCCP component of acetyl‐CoA carboxylase as a PII binding partner

The P_II family comprises a group of widely distributed signal transduction proteins. The archetypal function of P_II is to regulate nitrogen metabolism in bacteria. As P_II can sense a range of metabolic signals, it has been suggested that the number of metabolic pathways regulated by P_II may be much greater than described in the literature. In order to provide experimental evidence for this hypothesis a P_II protein affinity column was used to identify P_II targets in Azospirillum brasilense. One of the P_II partners identified was the biotin carboxyl carrier protein (BCCP), a component of the acetyl‐CoA carboxylase which catalyses the committed step in fatty acid biosynthesis. As BCCP had been previously identified as a P_II target in Arabidopsis thaliana we hypothesized that the P_II–BCCP interaction would be conserved throughout Bacteria. In vitro experiments using purified proteins confirmed that the P_II–BCCP interaction is conserved in Escherichia coli. The BCCP–P_II interaction required MgATP and was dissociated by increasing 2‐oxoglutarate. The interaction was modestly affected by the post‐translational uridylylation status of P_II; however, it was completely dependent on the post‐translational biotinylation of BCCP.