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Lecture

UNSUREPlants responding to cold and freezing stress.pdf

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Department
Biology
Course
BIOL 341
Professor
Kenton Ko
Semester
Winter

Description
Plants responding to cold and freezing stress Cold shock vs cold acclimationQuick cold shock damages plant Types of damageMembranesaffecting fluidity Affect ability to control what goes in and out important in cell organizationIce crystal formation plants try to restrict this to apoplast in cell wall and between cell and NOT inside the cellProtein denaturation affecting protein stability and ability to catalyze if temp goes too low too rigid or too high too loose distorted active siteOsmolyte and water loose freezing is like drought plants have no access to frozen water Membrane damageSemi fluid bilayer with cold becomes gellike and more rigidpacks together and changing environment the proteins embedded in it are working in like transporters cant move things across if rigid Dehydration damageWhen water turns to ice in apoplastlower water potential then in cell Water moves down gradient and leaves in extracellular space where the ice isdehydrationFast freezing problem because doesnt allow time for acclimationPhotosynthetic machineryParticularly sensitive to this damage because embedded in membraneChange consistency theyre working in changes ability to do their jobMore reactive oxygen species produced with high light but cold Plants defense against coldEhnaced membrane fluiditiy by modificationOsmolytes accumuation reduce freezing temp of water and lower soute conc to maybe prevent water from leavingChaperones help other proteins fold or refold to prevent denaturation do renaturationAntioxidant compounds to scavenge free radical speciesAntifreeze proteins slow control growth of crystalsSupercooling cell actively cools and maintain liquid state inside cell even below zeroABA one of most important stress hormones Induced in drought salinity and freezingtells plant there is some sort of water stress to induce plant response Mutants with no ABA tend to have decreased tolerance broadly to change in water stresses Ca2 influx during coldPlant fluorecesses when exposed to ca2 When put in cold stress can semiquantitavly measure how much ca2 is expressed Amount of ca2 correlated with ability to defend in cold stress response Membrane modificationChange composition desaturases convert saturated FAs to unsaturated FAs
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