Lolium perenne antifreeze protein, part of a freeze-tolerance strategy
Lauersen, Kyle J.
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Antifreeze proteins (AFPs) are a novel class of ice-binding stress response proteins produced by organisms which experience freezing at some point within their respective life histories. These proteins are structurally and evolutionarily diverse, are found in a range of different organisms, and are often related to stress or pathogen response proteins. AFPs are found in certain plant species, many of which are within the Poaceae family of monocotyledonous plants and are largely found within the Pooideae subfamily. Lolium perenne, (Lp) the perennial ryegrass, produces an antifreeze protein, LpAFP, and, like many plant AFPs, it does not dramatically depress the freezing point. However, LpAFP demonstrates great capacity in ice recrystallization inhibition (IRI). This robust IRI has led to interest in industrial applications of this protein, from cryoprotection to use as a frozen food additive, and most notably, to its potential use in transgenic crop enhancement. LpAFP has potential for crop enhancement strategies since its superior IRI allows controlled intercellular ice crystal formation, thus limiting the cellular membrane damage caused by freeze-thaw events. This thesis has generated a greater understanding of the nature of LpAFP, through selective characterization of its recombinant and native states, functional analysis through attempted gene knockdown, and investigation of its export pathways. In addition, it provides suggestions and strategies to work towards the development of transgenic trait applications.