Ferre, J. | Search bioRxiv

bioRxiv2023

Non-Stationary Dynamic Mode Decomposition

Many physical processes display complex high-dimensional time-varying behavior, from global weather patterns to brain activity. An outstanding challenge is to express high dimensional data in terms of a dynamical model that reveals their spatiotemporal structure. Dynamic Mode Decomposition is a means to achieve this goal, allowing the identification of key spatiotemporal modes through the diagonalization of a finite dimensional approximation of the Koopman operator. However, DMD methods apply best to time-translationally invariant or stationary data, while in many typical cases, dynamics vary across time and conditions. To capture this temporal evolution, we developed a method, Non-Stationary Dynamic Mode Decomposition (NS-DMD), that generalizes DMD by fitting global modulations of drifting spatiotemporal modes. This method accurately predicts the temporal evolution of modes in simulations and recovers previously known results from simpler methods. To demonstrate its properties, the method is applied to multi-channel recordings from an awake behaving non-human primate performing a cognitive task.

neuroscience↗

bioRxiv2020

Reduced levels of membrane-bound alkaline phosphatase in Vip3Aa-resistant Heliothis virescens

The Vip3Aa insecticidal protein from Bacillus thuringiensis (Bt) is produced by specific transgenic corn and cotton varieties for efficient control of target lepidopteran pests. The main threat to this technology is the evolution of resistance in targeted insect pests, thus understanding the mechanistic basis of resistance is crucial to deploy the most appropriate strategies for resistance management. In this work, a laboratory-selected colony of Heliothis virescens (Vip-Sel) highly resistant to the Vip3Aa protein was used to test whether an alteration of membrane receptors in the insect midgut might explain the resistance phenotype. Binding of 125I-labeled Vip3Aa to brush border membrane vesicles (BBMV) from 3rd instar larvae from Vip-Sel was not significantly different from binding in the reference susceptible colony. Interestingly, BBMV from Vip-Sel larvae show dramatically reduced levels of alkaline phosphatase activity, which was further confirmed by a strong down-regulation of the membrane-bound alkaline phosphatase 1 (HvmALP1) gene. However, its involvement as a receptor for the Vip3Aa protein was not supported by ligand blotting and viability assays with insect cells expressing HvmALP1. These data support that reduced alkaline phosphatase, previously observed in insect colonies resistant to Cry proteins from Bt, may also serve as an indirect marker that is not mechanistically involved in resistance to Vip3Aa. IMPORTANCEThe Vip3Aa insecticidal protein remains the only lepidopteran-specific trait in transgenic Bt crops with no cases of field-evolved resistance. While laboratory-selected resistance to Vip3A has been reported elsewhere, the mechanism for resistance is unknown. Results in this work show lack of significant Vip3Aa binding alterations in resistant and reference colonies of H. virescens. These observations are in contrast to most cases of high levels of resistance to insecticidal Bt proteins for which decreased binding is commonly detected. In addition, this study provides the first evidence of down-regulation of membrane bound alkaline phosphatase (mALP) associated with Vip3Aa resistance, a phenomenon commonly associated with resistance to Cry proteins from Bt. Results from this work suggest that mALP down-regulation may be a useful biomarker yet reject its direct participation in resistance to Vip3Aa.

microbiology↗