To acquire sufficient mineral nutrients such as phosphate (Pi) from the soil, most plants engage in symbiosis with arbuscular mycorrhizal (AM) fungi. Attracted by plant-secreted strigolactones, the fungi colonize the roots and form highly-branched hyphal structures called arbuscules inside inner cortex cells. The host plant must control the different steps of this interaction to maintain its symbiotic nature. However, how plants sense the amount of Pi obtained from the fungus, and how this determines the arbuscule lifespan, are far from understood. Here, we show that Medicago truncatula SPX-domain containing proteins SPX1 and SPX3 regulate root Pi starvation responses, in part by interacting with PHOSPHATE RESPONSE REGULATOR2, as well as fungal colonization and arbuscule degradation. SPX1 and SPX3 are induced upon Pi starvation but become more restricted to arbuscule-containing cells upon the establishment of symbiosis. This induction in arbuscule-containing cells is associated with the presence of cis-regulatory AW-boxes and transcriptional regulation by the WRINKLED1-like transcription factor WRI5a. Under Pi-limiting conditions, SPX1 and SPX3 facilitate the expression of the strigolactone biosynthesis gene DWARF27, which could help explain the increased fungal branching in response to root exudates. Later, in arbuscule-containing cells, SPX1 and SPX3 redundantly control arbuscule degradation. Thus, SPX proteins play important roles as phosphate sensors to maintain a beneficial AM symbiosis.

• Arguably, symbiotic arbuscular mycorrhizal (AM) fungi have the broadest host range of all fungi, being able to intracellularly colonize root cells in the vast majority of all land plants. This raises the question how AM fungi effectively deal with the immune systems of such a widely diverse range of plants. •Here, we studied the role of a nuclear-localization signal containing effector from Rhizophagus irregularis, called Nuclear Localized Effector1 (RiNLE1), that is highly and specifically expressed in arbuscules. •We show that RiNLE1 is able to translocate to the host nucleus where it interacts with the plant core nucleosome protein Histone 2B (H2B). RiNLE1 is able to impair the mono-ubiquitination of H2B, which results in the suppression of defense-related gene expression and enhanced colonization levels. • This study highlights a novel mechanism by which AM fungi can effectively control plant epigenetic modifications through direct interaction with a core nucleosome component. Homologs of RiNLE1 are found in a range of fungi that establish intimate interactions with plants, suggesting that this type of effector may be more widely recruited to manipulate host defense responses.

RW, et al. Following cytochrome c release, autophagy is inhibited during chemotherapy-induced apoptosis by caspase 8-mediated cleavage of Beclin 1.

A single and simple ortho-sulfonyl benzonitrile template was developed to achieve remote C-H olefination of six different classes of N-heterocycles. We demonstrate that, by varying precatalysts and conditions, the same template can be applied to the remote C-H activation of six structurally distinct heterocyclic scaffolds, and the site-selectivity can be predicted based on distance and geometry. Furthermore, this new development shows that template-directed remote C-H activation is possible through macrocyclopalladation processes with smaller ring sizes.