Stress-induced changes to the dendritic architecture of neurons have been demonstrated in numerous mammalian and invertebrate systems. Remodeling of dendrites varies tremendously among neuron types. During the stress-induced dauer stage of Caenorhabditis elegans, the IL2 neurons arborize to cover the anterior body wall. In contrast, the FLP neurons arborize to cover an identical receptive field during reproductive development. Using timecourse imaging, we show that branching between these two neuron types is highly coordinated. Furthermore, we find that the IL2 and FLP arbors have a similar dendritic architecture and use an identical downstream effector complex to control branching; however, regulation of this complex differs between stress-induced IL2 branching and FLP branching during reproductive development. We demonstrate that the unfolded protein response (UPR) sensor IRE-1, required for localization of the complex in FLP branching, is dispensable for IL2 branching at standard cultivation temperatures. Exposure of ire-1 mutants to elevated temperatures results in defective IL2 branching, thereby demonstrating a previously unknown genotype by environment interaction within the UPR. We find that the FOXO homolog, DAF-16, is required cell-autonomously to control arborization during stress-induced arborization. Likewise, several aspects of the dauer formation pathway are necessary for the neuron to remodel, including the phosphatase PTEN/DAF-18 and Cytochrome P450/DAF-9. Finally, we find that the TOR associated protein, RAPTOR/DAF-15 regulates mutually exclusive branching of the IL2 and FLP dendrites. DAF-15 promotes IL2 branching during dauer and inhibits precocious FLP growth. Together, our results shed light on molecular processes that regulate stress-mediated remodeling of dendrites across neuron classes.

Stress influences the shape of dendritic arbors in neurons. During the stress-induced dauer stage of Caenorhabditis elegans, the IL2 neurons arborize to cover the anterior body wall. In contrast, the FLP neurons arborize to cover the anterior body wall during non-dauer development.Previous work showed that the membrane-bound receptor DMA-1 regulates FLP branching as part of a larger protein complex. Using forward genetics, we show that the IL2 neurons also use the DMA-1 complex to regulate branching. To understand the coordination of the IL2s and FLPs we conducted a time-course examination of FLPs and found previously undescribed branching patterns indicating a neighborhood effect wherein the FLPs and IL2s in the anterior have differential branching compared to the more posteriorly located PVD arborizing neurons. To determine how the IL2s and FLPs differentially regulate branching, we examined several regulators of DMA-1 localization. We show that the unfolded protein response sensor IRE-1, required for FLP branching, is only required for dauer-specific branching at elevated temperatures. Interestingly, we found that ire-1 mutants have broad, organism-wide temperaturedependent effects on dauer remodeling, suggesting a previously undescribed role for IRE-1 in phenotypic plasticity. We also found that defects in other regulators of dauer remodeling including DAF-16/FOXO, DAF-9/Cytochrome P450, and DAF-18/PTEN are required for proper IL2 arborization, but dispensable for FLP branching. Interestingly, we find that TOR adaptor protein DAF-15/RAPTOR is both required for promoting IL2 branching and inhibiting precocious development of the FLPs. Our results demonstrate specific genotypic by environmental interactions regulating dendrite arborization.

Phosphite (Phi)-based fungicides are used to control the oomycete Phytophthora infestans which causes late blight disease, the most devastating disease in potatoes. In order to examine the effects of Phi-based fungicides on potato tubers through foliar or post-harvest application, a metabolite profiling approach based on gas chromatography coupled to mass spectrometry (GC-MS) has been established. A total of 132 metabolites were detected using the GC-MS approach. Among these, 34 metabolites were identified after normalization and annotated with a compound name with standard mass spectral library. Metabolomic analysis of Phi-treated plants showed significant differences in the levels of many metabolites especially amino acids. Multivariate statistical approaches, such as principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA), were employed to explore the relationships between metabolites to detect group differences. A good discrimination between the control and the Phi-treated plants was observed, which demonstrated that significant changes in the metabolite profile have been caused by the two different Phi applications (foliar or post-harvest). This finding suggests that the alteration of specific metabolite levels by accumulation of Phi can lead to resistance against the pathogen.