The disordered plant dehydrin Lti30 protects the membrane during water-related stress by cross-linking lipids

Abstract

Edited by Karen G. Fleming Dehydrins are intrinsically disordered proteins, generally expressed in plants as a response to embryogenesis and waterrelated stress. Their suggested functions are in membrane stabilization and cell protection. All dehydrins contain at least one copy of the highly conserved K-segment, proposed to be a membrane-binding motif. The dehydrin Lti30 (Arabidopsis thaliana) is up-regulated during cold and drought stress conditions and comprises six K-segments, each with two adjacent histidines. Lti30 interacts with the membrane electrostatically via pH-dependent protonation of the histidines. In this work, we seek a molecular understanding of the membrane interaction mechanism of Lti30 by determining the diffusion and molecular organization of Lti30 on model membrane systems by imaging total internal reflection-fluorescence correlation spectroscopy (ITIR-FCS) and molecular dynamics (MD) simulations. The dependence of the diffusion coefficient explored by ITIR-FCS together with MD simulations yields insights into Lti30 binding, domain partitioning, and aggregation. The effect of Lti30 on membrane lipid diffusion was studied on fluorescently labeled supported lipid bilayers of different lipid compositions at mechanistically important pH conditions. In parallel, we compared the mode of diffusion for short individual K-segment peptides. The results indicate that Lti30 binds the lipid bilayer via electrostatics, which restricts the mobility of lipids and bound protein molecules. At low pH, Lti30 binding induced lipid microdomain formation as well as protein aggregation, which could be correlated with one another. Moreover, at physiological pH, Lti30 forms nanoscale aggregates when proximal to the membrane suggesting that Lti30 may protect the cell by "cross-linking" the membrane lipids.Dehydrins are intrinsically disordered stress-related plant proteins that are up-regulated in cold and drought conditions

Analysing plasma membrane asymmetry of lipid organisation by fluorescence lifetime and correlation spectroscopy

“…Due to the domains, FLIM detects a mixture of lifetimes leading to a broad distribution of fluorescence lifetimes indicating the existence of a wide variety of transient assemblies 16 . In order to obtain complementary information to membrane organization as measured by FLIM we use ITIR-FCS, to measure membrane dynamics [18][19][20][21] . ITIR-FCS is an imaging modality that allows multiplexed FCS measurements on the whole region of interest simultaneously and provides spatially resolved diffusion coefficient and number of particle maps.…”

Dehydrins: an overview of current approaches and advancement

“…The molecular function and structural effect of DHNs is still unclear, but increasing evidence suggests that they play a role in maintaining the composition and functional dynamics of cell membranes (Eriksson et al, 2016). DHNs are located close to the membranes and their interactions change certain membrane properties, such as the phase transition temperature and water content (Eriksson et al, 2011;Gupta et al, 2019) DHNs can also bind to anionic phospholipids and the binding requires the presence of basic amino acids such as arginine and lysine in the binding sites of DHNs (Kooijman et al, 2007;Koag et al, 2009). The interaction of DHNs with charged lipids in the membranes occurs through electrostatic interactions (Koag et al, 2009;Eriksson et al, 2011).…”

“…Lipid binding at low pH was found to induce protein aggregation as well as microdomain formation. It has also been shown that Lti30 and other membrane-binding DHNs can maintain cell integrity by modulating the membrane structure during stress and possibly by lipid "crosslinking" (Gupta et al, 2019).…”

Functional Characteristics Analysis of Dehydrins in Larix kaempferi under Osmotic Stress

“…OsDHN-rab16d ( Oryza sativa ) combines with OsFKBP (a prolyl cis-trans isomerase) to form a complex that is involved in the signal transduction of the abscisic acid (ABA) response to drought stress in rice [ 18 ]. The Lti30 dehydrin in A.thaliana interacts with the membrane electrostatically where anionic lipid headgroups are exposed [ 19 , 20 ].…”