Aznar-Moreno, J. A. | Search bioRxiv

bioRxiv2026

Synaptotagmin-mediated plasma membrane homeostasis is required to recruit the endocytic machinery during cold stress

Endocytosis depends on plasma membrane (PM) lipid composition, yet how plants sustain endocytic machinery recruitment during stress remains unclear. We investigated whether synaptotagmins SYT1 and SYT3 function in membrane homeostasis and endocytosis in Arabidopsis thaliana. In this work, we revealed that cold stress reversibly blocked FM4-64 internalization in syt1syt3 double mutants by displacing peripheral and core TPC subunits from the PM. Loss of SYT1 reduced brassinosteroid receptor internalization during cold stress, while double mutants showed enhanced brassinosteroid signaling. SYTs and VAP27 genes showed a condition-dependent genetic interaction in endocytosis: the syt1/vap27-1/vap27-3 triple mutant resembles vap27-1/vap27-3 under control conditions and syt1 during cold stress, suggesting overlapping contributions to endocytic regulation. Using molecular dynamics simulations of protein-membrane interactions, phosphoinositide depletion combined with increased diacylglycerol weakened TPC core membrane association. Our findings identify SYT1 and SYT3 as essential components for sustaining endocytosis during abiotic stress and support a model in which lipid homeostasis at endoplasmic reticulum-PM contact sites preserves the membrane composition required for TPC-dependent endocytosis.

plant biology↗

bioRxiv2020

Temporal changes in metabolism late in seed development affect biomass composition in soybean

The inverse correlation between protein and oil production in soybeans is well-documented; however, it has been based primarily on the composition of mature seeds. Though this is the cumulative result of events over the course of soybean seed development, it does not convey information specific to metabolic fluctuations during developmental growth regimes. Maternal nutrient supply via seed coat exudate measurements and metabolite levels within the cotyledon were assessed across development to identify trends in the accumulation of central carbon and nitrogen metabolic intermediates. Active metabolic operation during late seed development was probed through transient labeling with 13C substrates. The results indicated: i) a drop in lipid during seed maturation with a concomitant increase in carbohydrates, ii) a transition from seed filling to maturation phase characterized by quantitatively balanced changes in the carbon use and CO2 release, iii) changes in measured carbon and nitrogen resources supplied maternally over development, iv) 13C metabolites processed through gluconeogenesis towards sustained carbohydrate accumulation as the maternal nutrient supply diminishes, and v) oligosaccharide biosynthetic metabolism during seed coat senescence at maturation. These results highlight temporal engineering targets for altering final biomass composition to increase the value of soybeans and a path to breaking the inverse seed protein and oil correlation. One-sentence summaryAssessment of temporal changes in metabolism during soybean seed development indicated that lipid turnover during maturation contributes carbon for gluconeogenic production of carbohydrates.

plant biology↗