Biology subjects

Stroock, A.

Publications and source records attributed to Stroock, A..

4 recordsLinked to original sources

bioRxiv2024

A unified framework for hydromechanical signaling: Do plant signals go with the flow?

Local wounding in plants triggers signals that travel locally within the wounded leaf or systemically through the vasculature to distal leaves. The transmission mechanisms of this ubiquitous class of signals remain poorly understood. Here, we develop a unifying framework based on poroelastic dynamics to study two coupled biophysical processes - propagation of pressure changes and transmission of chemical elicitors via mass flows driven by these pressure changes - as potential mechanisms for the initiation and propagation of wound-induced signals. We show that rapid pressure changes in the xylem can transmit mechanical information across the plant, while their coupling with neighboring non-vascular tissue drives swelling and mass flow that can transport chemical elicitors to distal leaves. We confront our model predictions with signaling dynamics measurements in several species, and show that the poroelastic model captures observed mechanical, biochemical, and electrophysiological signals. This framework provides a valuable foundation for assessing mechanisms of signal transmission and for designing future experiments to elucidate factors involved in signal initiation, propagation, and target elicitation.

plant biology↗

bioRxiv2023

Localized measurements of water potential reveal large loss of conductance in living tissues of maize leaves

The water status of the living tissue in leaves between the xylem and stomata (outside xylem zone - OXZ) play a critical role for plant function and global mass and energy balance but has remained largely inaccessible. We resolve the local water relations of OXZ tissue using a nanogel reporter of water potential ({psi}), AquaDust, that enables an in-situ, non-destructive measurement of both{psi} of xylem and highly localized{psi} at the terminus of transpiration in the OXZ. Working in maize, these localized measurements reveal gradients in the OXZ that are several fold larger than those based on conventional methods, and values of{psi} in the mesophyll apoplast well below the macroscopic turgor loss potential. We find a strong loss of hydraulic conductance in both the bundle sheath and the mesophyll with decreasing xylem potential but not with evaporative demand. Our measurements suggest an active role played by the OXZ in regulating the transpiration path and our methods provide novel means to study this phenomenon.

physiology↗

bioRxiv2022

Floral humidity as a signal--not a cue--in a nocturnal pollination system

Although visual and olfactory floral signals attract pollinators from a distance, at the flowers threshold, pollinators can use floral humidity as an index cue for nectar presence. We evaluate the role of floral humidity in the Datura wrightii-Manduca sexta nocturnal pollination system. In addition to our finding that M. sexta shows strong innate attraction toward humid flowers, we identify the hygrosensing sensillum on their antennae, demonstrate its extreme sensitivity to minute changes in RH, and observe the elimination of moths behavioral preference towards humid flowers following experimental occlusion of the sensilla. Despite Manducas attraction toward humid flowers, we find that floral humidity is not a reliable cue for nectar presence in this system. While Datura floral headspace sustains an enormous humidity gradient, it is not a consequence of nectar evaporation, but an outcome of gas exchange through floral stomata and is decoupled from nectar presence. Using interdisciplinary tools, we demonstrate the function of floral humidity as an attractive signal, not a cue, in this pollination system, thus showcasing an underappreciated modality by which flowers may manipulate their visitors.

ecology↗

bioRxiv2019

A VEGF reaction-diffusion mechanism that selects variable densities of endothelial tip cells

The patterned differentiation of endothelial cells into tip and stalk cells represents an important step in the process of angiogenic sprouting. Vascular biologists hypothesize that changes in the density and overall structure of the vasculature can be traced in part to changes in the number of tip cells selected in the endothelium prior to sprout formation. However, the dominant hypotheses for tip cell selection invoke lateral inhibition via Notch; this juxtacrine mechanism predicts that a fixed fraction of endothelial cells become tip cells through a pattern-forming instability. Here, we present and analyze a hypothetical mechanism for tip cell selection that is based on endothelial competition for diffusible vascular endothelial growth factor (VEGF); this mechanism predicts that variable densities of tip cells emerge depending on the local (paracrine) production rate of VEGF. First, we hypothesize a network of VEGF signaling and trafficking based on previous experimental findings that could allow internalization of VEGF to occur with positive feedback. We formalize the hypothesis into a set of nonlinear ordinary differential equations and perform linear stability analysis to elucidate a general criterion for tip cell pattern formation under the mechanism. We use numerical integration to explore the nonlinear dynamics and final steady-states of tip cell patterns under this mechanism; the observed density of tip cells can be tuned from 10% to 84%. We conclude with proposals of future experiments and computational studies to explore how competitive consumption of diffusible VEGF may play a role in determining vascular structure.\n\nStatement of SignificanceThe patterned differentiation of endothelial cells into tip and stalk cells represents an important step in the process of blood vessel growth. Vascular biologists hypothesize that changes in the density and overall structure of the vasculature can be traced in part to changes in the number of tip cells selected during angiogenesis. However, the dominant hypotheses for tip cell selection predict that a locally fixed fraction of endothelial cells become tip cells following stimulation by vascular endothelial growth factor (VEGF). Here, we present and analyze a hypothetical mechanism for tip cell selection based on endothelial competition for diffusible VEGF; this mechanism predicts that variable densities of tip cells emerge depending on the local production rate of VEGF.

systems biology↗