In Arabidopsis (Arabidopsis thaliana), the Pseudomonas syringae effector proteins AvrB and AvrRpm1 are both detected by the RESISTANCE TO PSEUDOMONAS MACULICOLA1 (RPM1) disease resistance (R) protein. By contrast, soybean (Glycine max) can distinguish between these effectors, with AvrB and AvrRpm1 being detected by the Resistance to Pseudomonas glycinea 1b (Rpg1b) and Rpg1r R proteins, respectively. We have been using these genes to investigate the evolution of R gene specificity and have previously identified RPM1 and Rpg1b. Here, we report the cloning of Rpg1r, which, like RPM1 and Rpg1b, encodes a coiledcoil (CC)-nucleotide-binding (NB)-leucine-rich repeat (LRR) protein. As previously found for Rpg1b, we determined that Rpg1r is not orthologous with RPM1, indicating that the ability to detect both AvrB and AvrRpm1 evolved independently in soybean and Arabidopsis. The tightly linked soybean Rpg1b and Rpg1r genes share a close evolutionary relationship, with Rpg1b containing a recombination event that combined a NB domain closely related to Rpg1r with CC and LRR domains from a more distantly related CC-NB-LRR gene. Using structural modeling, we mapped polymorphisms between Rpg1b and Rpg1r onto the predicted tertiary structure of Rpg1b, which revealed highly polymorphic surfaces within both the CC and LRR domains. Assessment of chimeras between Rpg1b and Rpg1r using a transient expression system revealed that AvrB versus AvrRpm1 specificity is determined by the C-terminal portion of the LRR domain. The P. syringae effector AvrRpt2, which targets RPM1 INTERACTOR4 (RIN4) proteins in both Arabidopsis and soybean, partially blocked recognition of both AvrB and AvrRpm1 in soybean, suggesting that both Rpg1b and Rpg1r may detect these effectors via modification of a RIN4 homolog.
By monitoring or following trails layed on the ground a mobile robot can perform several useful navigation tasks. An example would be following a trail layed on an outwurd journey in order to laterfind the way back to the starting point. This paper describes the latest stage in the development of a robot navigalion system based on laying down and detecting trails of volatile chemicals. Previously a prototype olfactory sensor was developed which showed the feasibility of having a mobile robot follow an odour trail on the floor. This prototype sensor has now been improved by managing airflow in the vicinity of the sensor. This has decreased the sensor response time and improved rejeclion of spurious odour signuls carried by mirflow in the room. A simple and effective applicalor has also hccn developed for laying odour trails. 1: IntroductionIn this paper we describe the dcvclopmcnt of an improved robotic olfactory sensor suitablc for detecting and tracking odour markings on the floor. When combincd with an odour applicator there arc many potential uses for such an odour marking and detection systcm. Insects survive, fccd and reproduce very effectively -especially considering their relatively small nervous system. The honcy bee is estimated to have 850,000 neurones in its brain [ l ] compared to 10,000,000,000 for homo sapiens 121. In orticr to operate effectively in the variable and unstrricturcd real world environment, insects employ many strategics. Laying down and detecting odours is the basis of scvcral of these strategies. Similar techniques can bc implcmentcd to improve the competence of robotic systems.It has been shown that honeybees usc an olkictory marker to increase their efficiency when gathcring ncctar [3]. After visiting a flower and gathering its nectar the honeybee marks the flower with a short-lived odour. Thc odour provides a warning that h e flower has no1 had timc to make more nectar. Honeybees dctecting the odour will not waste time landing on a flower that has no ncctar. Robotic floor cleaners could use a similar strategy to mark areas of the floor that have been cleancd already 131. In this way the floor cleaner will not wastc timc cleaning parts of the floor more than once. A robot night watchman could 1050-4729/94 $03.00 0 1994 IEEE inark its path with an odour trail. Arriving at a junction in its path the robot would choose the path marked with the oldcst odour trail. In this way one or multiple night watchincn robots could provide even coverage without central conuol, planning or dircct communication between robols.Ants cstablish and maintain an odour trail bctween their nesi and a sourcc ol' food 151. The trail guides both outgoing ants and incoming ants ladcn with food. A similar tcchniquc could bc employcd by mobile robots to transport largc quantities of materiel. A path between the starting point and goal could bc surveyed by a mobile robot cquippcd with a rangc of navigation sensors and the intclligcncc ncccssary to dctcrmine a suitable path to the goal by intcrprcting the scnsor ...
The Pseudomonas syringae effector AvrB triggers a hypersensitive resistance response in Arabidopsis and soybean plants expressing the disease resistance (R) proteins RPM1 and Rpg1b, respectively. In Arabidopsis, AvrB induces RPM1-interacting protein kinase (RIPK) to phosphorylate a disease regulator known as RIN4, which subsequently activates RPM1-mediated defenses. Here, we show that AvrPphB can suppress activation of RPM1 by AvrB and this suppression is correlated with the cleavage of RIPK by AvrPphB. Significantly, AvrPphB does not suppress activation of RPM1 by AvrRpm1, suggesting that RIPK is not required for AvrRpm1-induced modification of RIN4. This observation indicates that AvrB and AvrRpm1 recognition is mediated by different mechanisms in Arabidopsis, despite their recognition being determined by a single R protein. Moreover, AvrB recognition but not AvrRpm1 recognition is suppressed by AvrPphB in soybean, suggesting that AvrB recognition requires a similar molecular mechanism in soybean and Arabidopsis. In support of this, we found that phosphodeficient mutations in the soybean GmRIN4a and GmRIN4b proteins are sufficient to block Rpg1b-mediated hypersensitive response in transient assays in Nicotiana glutinosa. Taken together, our results indicate that AvrB and AvrPphB target a conserved defense signaling pathway in Arabidopsis and soybean that includes RIPK and RIN4.
Beer draught lines are frequently contaminated with biofilm-forming microorganisms, which forces retailers to spend considerable time and money cleaning and replacing lines. In light of this financial burden, draught tubing composition was examined for its role in the prevention of biofouling in beer lines. Three types of draught tubing - vinyl, polyethylene, and nylon barrier - were inoculated with a combination of biofilm-forming microorganisms (Hafnia paralvei, Raoultella planticola, Pediococcus damnosus and Saccharomyces cerevisiae) and used to simulate a bar environment for sixteen weeks. Following simulation, the degree of biofouling in each draught line was determined by spectrophotometry and microscopy. Absorption values and fluorescence images showed that nylon barrier tubing was superior to the other lines at resisting biofilm maturation.These results suggest that tubing composition plays a significant role in the prevention of biofilm formation in beer draught lines and supports the adoption of nylon barrier tubing as an effective strategy against biofouling in a variety of applications.
Electric field sensing exists in a number of aquatic animals, which use this ability to sense their environments. This paper provides a preliminary report of a project investigating the use of electric "field sensing for navigation and guidance of a robot submersible crag.
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