Autophagy is essential for prolonging yeast survival during nutrient deprivation; however, this report shows that some autophagy proteins may also be accelerating population death in those conditio...

Eukaryotes use a common set of genes to perform two mechanistically similar autophagic processes. Bulk autophagy harvests proteins nonselectively and reuses their constitutents when nutrients are s...

Background: Pyridine-2,6-bis(thiocarboxylic acid) (pdtc) is a small secreted metabolite that has a high affinity for transition metals, increases iron uptake efficiency by 20% in Pseudomonas stutzeri, has the ability to reduce both soluble and mineral forms of iron, and has antimicrobial activity towards several species of bacteria. Six GenBank sequences code for proteins similar in structure to MoeZ, a P. stutzeri protein necessary for the synthesis of pdtc. Results: Analysis of sequences similar to P. stutzeri MoeZ revealed that it is a member of a superfamily consisting of related but structurally distinct proteins that are members of pathways involved in the transfer of sulfur-containing moieties to metabolites. Members of this family of enzymes are referred to here as MoeB, MoeBR, MoeZ, and MoeZdR. MoeB, the molybdopterin synthase activating enzyme in the molybdopterin cofactor biosynthesis pathway, is the most characterized protein from this family. Remarkably, lengths of greater than 73% nucleic acid homology ranging from 35 to 486 bp exist between Pseudomonas stutzeri moeZ and genomic sequences found in some Mycobacterium, Mesorhizobium, Pseudomonas, Streptomyces, and cyanobacteria species. Conclusions: The phylogenetic relationship among moeZ sequences suggests that P. stutzeri may have acquired moeZ through lateral gene transfer from a donor more closely related to mycobacteria and cyanobacteria than to proteobacteria. The importance of this relationship lies in the fact that pdtc, the product of the P. stutzeri pathway that includes moeZ, has an impressive set of capabilities, some of which could make it a potent pathogenicity factor.

In this study, we show that the potato ( Solanum tuberosum ) pattern recognition receptor (PRR) NEMATODE-INDUCED LEUCINE-RICH REPEAT (LRR)-RLK1 (StNILR1) functions as a dual receptor, recognizing both nematode-associated molecular pattern ascaroside #18 (Ascr18) and plant hormone brassinosteroid (BR) to activate two different physiological outputs: pattern-triggered immunity (PTI) and BR response. Ascr18/BR-StNILR1 signaling requires the coreceptor potato BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED RECEPTOR KINASE 1 (StBAK1) and perception of either ligand strengthens StNILR1 interaction with StBAK1 in plant cells. Significantly, the parasitically successful potato cyst nematode ( Globodera pallida ) utilizes the effector RHA1B, which is a functional ubiquitin ligase, to target StNILR1 for ubiquitination-mediated proteasome-dependent degradation, thereby countering Ascr18/BR-StNILR1-mediated PTI in potato and facilitating nematode parasitism. These findings broaden our understanding of PRR specificity and reveal a nematode parasitic mechanism that targets a PTI signaling pathway.

Potato cyst nematodes (PCNs), such as Globodera pallida and Globodera rostochiensis, are some of the most agriculturally and economically important pests of potato. Upon nematode infection, a principal component of plant defense is the generation of the reactive oxygen species (ROSs). ROSs are highly toxic molecules that cause damage to pathogens and host alike. To infect the plant, nematodes protect themselves from ROSs by activating their own antioxidant processes and ROS scavenging enzymes. One of these enzymes is a superoxide dismutase (SOD; EC 1.15.1.1), which prevents cellular damage by catalyzing conversion of the superoxide radical (O₂^−·) to hydrogen peroxide (H₂O₂) and molecular oxygen (O₂). We have isolated a putatively secreted isoform of a Cu–Zn SOD (SOD-3) from G. pallida and localized the expression of this gene in the posterior region of the nematode. Furthermore, we studied the expression of the SOD-3 gene during early parasitic stages of infection (24 to 72 h) in the susceptible potato cultivar Desiree, the resistant potato cultivar Innovator, and an immune host, Solanum sisymbriifolium. The SOD-3 gene was significantly upregulated, regardless of the host type; however, the expression pattern differed between the susceptible and the resistant or immune hosts. This finding suggests that SOD-3 gene is responding to infection in plant roots differently depending on whether the nematode is experiencing a compatible or an incompatible interaction.

The plant-parasitic nematode Globodera pallida is an obligate biotroph that only reproduces on select species in the Solanum family. The establishment of the feeding site, the syncytium, involves secretion of effectors into the plant cell to combat the plant defense response and facilitate transformation of root cells into the syncytium. Despite the important predicted roles of effectors in the plant−pathogen interactions, the functionality of G. pallida effectors is largely unknown. In this study, we identified and characterized a G. pallida effector protein disulfide isomerase (GpPDI1). GpPDI1 contains two thioredoxin domains that function together to reduce disulfide bonds, as manifested by the nullification of enzymatic activity when either domain is absent. The transcript of GpPDI1 is localized in the dorsal gland of the nematode during the J2 stage. In addition, GpPDI1 can trigger defense-related cell death in Nicotiana benthamiana and tomato (Solanum lycopersicum) leaf tissue and localizes in the plant host cell’s cytoplasm and nucleus when transiently expressed in plant cells. Significantly, the ability of elicitation of cell death is not dependent on the enzymatic activity of GpPDI1 or correlated with the subcellular distribution of GpPDI1, suggesting that a nondisulfide reducing function or structural feature of GpPDI1 is responsible for the recognition by the host immune system to elicit cell death.