Dynamic localization of a helper NLR at the plant-pathogen interface underpins pathogen recognition.

Plants employ sensor-helper pairs of NLR immune receptors to recognize pathogen effectors and activate immune responses. Yet, the subcellular localization of NLRs pre- and postactivation during pathogen infection remains poorly understood. Here, we show that NRC4, from the "NRC" solanaceous helper NLR family, undergoes dynamic changes in subcellular localization by shuttling to and from the plant-pathogen haustorium interface established during infection by the Irish potato famine pathogen Phytophthora infestans. Specifically, prior to activation, NRC4 accumulates at the extrahaustorial membrane (EHM), presumably to mediate response to perihaustorial effectors that are recognized by NRC4-dependent sensor NLRs. However, not all NLRs accumulate at the EHM, as the closely related helper NRC2 and the distantly related ZAR1 did not accumulate at the EHM. NRC4 required an intact N-terminal coiled-coil domain to accumulate at the EHM, whereas the functionally conserved MADA motif implicated in cell death activation and membrane insertion was dispensable for this process. Strikingly, a constitutively autoactive NRC4 mutant did not accumulate at the EHM and showed punctate distribution that mainly associated with the plasma membrane, suggesting that postactivation, NRC4 may undergo a conformation switch to form clusters that do not preferentially associate with the EHM. When NRC4 is activated by a sensor NLR during infection, however, NRC4 forms puncta mainly at the EHM and, to a lesser extent, at the plasma membrane. We conclude that following activation at the EHM, NRC4 may spread to other cellular membranes from its primary site of activation to trigger immune responses.

Enhanced germination and electrotactic behaviour ofPhytophthora palmivorazoospores in weak electric fields.

Soil-dwelling microorganisms use a variety of chemical and physical signals to navigate their environment. Plant roots produce endogenous electric fields which result in characteristic current profiles. Such electrical signatures are hypothesised to be used by pathogens and symbionts to track and colonise plant roots. The oomycete pathogenPhytophthora palmivoragenerates motile zoospores which swim towards the positive pole when exposed to an external electric fieldin vitro. Here, we provide a quantitative characterization of their electrotactic behaviour in 3D. We found that a weak electric field (0.7-1.0 V cm-1) is sufficient to induce an accumulation of zoospore at the positive pole, without affecting their encystment rate. We also show that the same external electric field increases the zoospore germination rate and orients the germ tube's growth. We conclude that several early stages of theP. palmivorainfection cycle are affected by external electric fields. Taken together, our results are compatible with the hypothesis that pathogens use plant endogenous electric fields for host targeting.

Family and Educational Strategies for Cyberbullying Prevention: A Systematic Review.

Cyberbullying can be described as a form of bullying carried out by an individual or a group through digital media with the intention to harm others. It has been recognized as a public health issue recently; however, of the vast literature published in recent years on the phenomenon, only a small part concerns strategies adopted to prevent and combat cyberbullying, and the effectiveness of these strategies appears to be scarce. We conducted a systematic review of the literature published in the last five years about different interventions studied to prevent and contrast cyberbullying. Our results show how most of the strategies currently developed focus on the educational aspect, involving schools and families. Other authors describe technology-based practices to set programs to reduce and prevent cyberbullying through the usage of digital instruments, the same used by minors themselves. Finally, remaining tactics use a more comprehensive approach, mixing tools already in use in the aforementioned strategies. Cyberbullying requires wide-ranging methods to combat it, involving the contribution of mental health professionals, educators, and digital experts cooperating synergically. Prevention and contrast instruments should be defined, implemented, tested, and combined in order to deal with cyberbullying.

An N-terminal motif in NLR immune receptors is functionally conserved across distantly related plant species.

The molecular codes underpinning the functions of plant NLR immune receptors are poorly understood. We used in vitro Mu transposition to generate a random truncation library and identify the minimal functional region of NLRs. We applied this method to NRC4-a helper NLR that functions with multiple sensor NLRs within a Solanaceae receptor network. This revealed that the NRC4 N-terminal 29 amino acids are sufficient to induce hypersensitive cell death. This region is defined by the consensus MADAxVSFxVxKLxxLLxxEx (MADA motif) that is conserved at the N-termini of NRC family proteins and ~20% of coiled-coil (CC)-type plant NLRs. The MADA motif matches the N-terminal α1 helix of Arabidopsis NLR protein ZAR1, which undergoes a conformational switch during resistosome activation. Immunoassays revealed that the MADA motif is functionally conserved across NLRs from distantly related plant species. NRC-dependent sensor NLRs lack MADA sequences indicating that this motif has degenerated in sensor NLRs over evolutionary time.