Improving germination performance through a mechanistic understanding of seed priming

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The project will address the important agricultural issue of improving seed germination, in particular in seeds that are pre-treated to enhance germination processes. Seeds underpin sustainable agriculture and food security, providing the majority of global food principally as cereals and legumes. Seeds also play essential roles in crop propagation, and optimal yields require high vigour seed lots that provide rapid, uniform germination and seedling establishment that is tolerant of stress conditions. Germination and seedling establishment are routinely improved in commercial species by pre-treatment of seeds prior to germination. This process, termed priming, involves controlled hydration to activate pre-germinative processes without completion of germination. However, the molecular basis of priming, and the associated loss of seed longevity in primed seeds, is not well understood to-date, but cellular repair processes are likely to have key roles.In this project, we will uncover the molecular mechanisms which confer vigour enhancement in priming, and establish the genetic basis for the associated loss of seed longevity. This builds on our recent discovery that the mechanisms that mediate responses to DNA damage in plants control germination. In dry seeds there is a steady accumulation of background DNA damage which is exacerbated by adverse conditions during seed maturation, storage and germination. This leads to extremely high levels of genome stress experienced by the embryo upon seed rehydration. High levels of DNA repair activity are required early in germination to reverse this damage before growth resumes, as failure in repair processes results in severe mutagenesis of genetic material, impaired development and ultimately death of the plant. Sensing of DNA damage leads to rapid activation of cellular signalling programmes early in germination that function to delay germination, allowing extended time for repair, or activate cell death. As priming functions to reverse this delay to germination, we hypothesise a central role for DNA repair and damage signalling processes in the priming mechanism. Here we will use genetic, biochemical and high throughput analytical approaches to reveal the molecular link between genome integrity and priming, establishing the mechanistic basis of seed priming for the enhancement of seed germination.Primed seeds display reduced storability, resulting in substantial yield economic losses for the seed industry. The underlying causes of this reduced longevity is unknown. However, we recently identified that seeds defective in the repair of chromosomal breaks display highly reduced longevity after priming. This important new result reveals a novel link between increased DNA damage in primed seeds with the accelerated loss of germination potential. We will build on these results to reveal the molecular basis for the reduced longevity of primed seeds, identifying the requirement for specific repair activities that mitigate reduced shelf-life post-priming. Furthermore, identifying the signalling responses associated with reduced longevity provides a powerful approach to reveal the underlying cellular causes of the short lifespan of primed seeds.The ultimate aim of this project is to develop novel lines of plants with improved longevity after priming through modulating the activity of these DNA repair factors. We will test the potential of key factors to genetically improve the resilience of seed germination in Arabidopsis and Brassica oleracea, a crop species important to UK agriculture. These approaches will address the long-standing problem that seeds of many vegetable species suffer from poor germination and establishment after storage, resulting in reduced crop yields. Taken together, the project will enable the application of technologies based on our knowledge of plant stress responses to deliver high quality seeds and support sustainable agriculture.