The role of FMT and FIS1A in mitochondrial morphology and salt stress in Arabidopsis thaliana

Salt stress is known to have severe effects on plant health and fecundity, and mitochondria are known to be an essential part of the plant salt stress response. Arabidopsis thaliana serves as an excellent model to study the effects of salt stress as well as mitochondrial morphology. Arabidopsis contains several homologues to known mitochondrial proteins, including the fission protein FIS1A, and FMT, a homologue of the CLU subfamily. We sought to examine the effects of salt stress on knockout lines of FIS1A and FMT, as well as a transgenic line overexpressing FMT (FMT-OE) in columella cells in the root cap of Arabidopsis. fmt mutants displayed defects in both root and leaf growth, as well as a delay in flowering time. These mutants also showed a pronounced increase in mitochondrial clustering and number. FMT-OE mutants displayed severe defects in germination, including a decrease in total germination, and an increase in the number of days to germination. fis1A mutants exhibited shorter roots and slightly shorter leaves, as well as a tendency towards random mitochondrial clustering in root cells. Salt stress was shown to affect various mitochondrial parameters, including an increase in mitochondrial number and clustering, as well as a decrease in mitochondrial area. These results reveal a previously unknown role for FMT in germination and flowering in Arabidopsis, as well as insight into the effects of salt stress on mitochondrial morphology. FMT, along with FIS1A, may also help to regulate mitochondrial number and clustering, as well as root and leaf growth, under both control and salt-stressed conditions. This has implications for both FMT and FIS1A in whole-plant morphology as well as the plant salt stress response

The Interaction of Early Salt Stress-Induced 2 (ESI2) and the Ran G Protein in Arabidopsis

The Early Salt Stress-Induced 2 protein, ESI2, was identified as an interacting protein with the GTP-binding protein RAN via a His6-tag pull-down assay and by bimolecular fluorescent complementation. Fluorescent protein fusions transiently expressed in Nicotiana benthamiana were observed using confocal fluorescent microscopy. The proteins fused to independent fluorescent partners localized to separate cellular compartments, with RAN primarily localized to the nucleus and ESI2 localized primarily to the tonoplast and cytoplasm. This interaction suggests a potential mechanism for the role of ESI2 in the sequestration of RAN and possible regulation of cell division in response to stress. To further explore the role of ESI2, the protein was overexpressed in Arabidopsis however plant phenotypes were not found to differ from wild type plants

Heterotrimeric Gα subunit from wheat (Triticum aestivum), GA3, interacts with the calcium-binding protein, Clo3, and the phosphoinositide-specific phospholipase C, PI-PLC1

The canonical Gα subunit of the heterotrimeric G protein complex from wheat (Triticum aestivum), GA3, and the calcium-binding protein, Clo3, were revealed to interact both in vivo and in vitro and Clo3 was shown to enhance the GTPase activity of GA3. Clo3 is a member of the caleosin gene family in wheat with a single EF-hand domain and is induced during cold acclimation. Bimolecular Fluorescent Complementation (BiFC) was used to localize the interaction between Clo3 and GA3 to the plasma membrane (PM). Even though heterotrimeric G-protein signaling and Ca2+ signaling have both been shown to play a role in the response to environmental stresses in plants, little is known about the interaction between calcium-binding proteins and Gα. The GAP activity of Clo3 towards GA3 suggests it may play a role in the inactivation of GA3 as part of the stress response in plants. GA3 was also shown to interact with the phosphoinositide-specific phospholipase C, PI-PLC1, not only in the PM but also in the endoplasmic reticulum (ER). Surprisingly, Clo3 was also shown to interact with PI-PLC1 in the PM and ER. In vitro analysis of the protein–protein interaction showed that the interaction of Clo3 with GA3 and PI-PLC1 is enhanced by high Ca2+ levels. Three-way affinity characterizations with GA3, Clo3 and PI-PLC1 showed the interaction with Clo3 to be competitive, which suggests that Clo3 may play a role in the Ca2+-triggered feedback regulation of both GA3 and PI-PLC1. This hypothesis was further supported by the demonstration that Clo3 has GAP activity with GA3

Generally-healthy individuals with aberrant bowel movement frequencies show enrichment for microbially-derived blood metabolites associated with impaired kidney function.

OBIECTIVE: Bowel movement frequency (BMF) variation has been linked to changes in the composition of the human gut microbiome and to many chronic conditions, like metabolic disorders, neurodegenerative diseases, chronic kidney disease (CKD), and other intestinal pathologies like irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). Slow intestinal transit times (constipation) are thought to lead to compromised intestinal barrier integrity and a switch from saccharolytic to proteolytic fermentation within the microbiota, giving rise to microbially-derived toxins that may make their way into circulation and cause damage to organ systems. However, these phenomena have not been characterized in generally-healthy populations, and the connections between microbial metabolism and the early-stage development and progression of chronic disease remain underexplored. DESIGN: Here, we examine the phenotypic impact of BMF variation across a cohort of over 2,000 generally-healthy, community dwelling adults with detailed clinical, lifestyle, and multi-omic data. RESULTS: We show significant differences in key blood plasma metabolites, proteins, chemistries, gut bacterial genera, and lifestyle factors across BMF groups that have been linked, in particular, to inflammation and CKD severity and progression. DISCUSSION: In addition to dissecting BMF-related heterogeneity in blood metabolites, proteins, and the gut microbiome, we identify self-reported diet, lifestyle, and psychological factors associated with BMF variation, which suggest several potential strategies for mitigating constipation and diarrhea. Overall, this work highlights the potential for managing BMF to prevent disease. WHAT IS ALREADY KNOWN ABOUT THIS TOPIC: Constipation and diarrhea are linked to several chronic diseases, like IBD, CKD, and neurodegenerative disorders. Chronic constipation, in particular, is associated with the increased production of microbially-derived uremic toxins in the gut due to an ecosystem-wide switch from fiber fermentation to protein fermentation. A build-up of these gut-derived toxins in blood, like p-cresol, has been associated with CKD disease progression and severity. WHAT THIS STUDY ADDS: While prior work has demonstrated associations between microbially-derived uremic toxins, constipation, and CKD severity/progression, here we show similar signatures in a generally-healthy cohort. Overall, we map out the molecular phenotypic effects of aberrant BMFs across individuals without any apparent disease, and show how these effects precede, and may contribute to, the development of chronic disease. We find that certain lifestyle and dietary patterns, like higher levels of exercise, reduced anxiety levels, a more plant-based diet, and drinking more water, are associated with a more optimal BMF range. HOW THIS STUDY MIGHT AFFECT RESEARCH POLICY OR PRACTICE: Overall, we suggest that even mild levels of chronic constipation may cause damage to organ systems over time and ultimately give rise to chronic diseases, like CKD or neurodegeneration. These findings pave the way for future research into early interventions for individuals at risk of developing chronic diseases related to BMF abnormalities. Managing BMF abnormalities prior to disease development may be an important disease prevention strategy, but this will require further evidence through longitudinal human intervention trials