Regulation of seed dormancy and its link to flowing time in the annual life cycle of plants.

Dormancy is an innate seed property that defines the response of the seed to environmental conditions and therefore the season and precise conditions in which the seed germinates. Understanding seed dormancy and how it is regulated in response to the prevailing environment is therefore crucially important for the establishment of both crops and wild plants. The timing and success of seedling establishment has a direct impact on the sustainable production of profitable crops. In weeds, and in annual plants in more natural situations, it is a major contributor in determining the timing of the whole life cycle, and therefore the competitive nature of weeds and the balance of natural plant populations. Our current knowledge of dormancy has increased greatly in recent years based largely on the use of Arabidopsis as a model system in controlled laboratory environments and models for its control have been developed that centre on a hormone balance between promoting (gibberellins) and inhibiting (abscisic acid) hormones. However, most molecular studies have concentrated on the primary dormant state in which seeds are shed from the mother plant and comparatively little is known of how dormancy is regulated as it enters dormancy cycling (i.e. the level of dormancy goes up and down with seasons) in the soil seed bank. Our previous work has shown that the transitional primary dormant state differs significantly from the more deeply dormant states that follow during cycling. More recently using a highly dormant ecotype from the Cape Verdi islands, (Cvi), we investigated molecular changes during dormancy cycling in field soils. This approach revealed a previously unforeseen temporal organisation of hormone signalling that responds to seasonal environmental signals. In the proposed work we intend to build upon this advance to understand more about how dormancy operates in the field environment and how in conjunction with flowering time it determines the life cycle of annual plants. The work will also help us to understand how natural variation in plants facilitates adaption to climate and environmental change The aims of the project are therefore twofold, firstly to increase understanding of the regulation of Arabidopsis seed dormancy in a field setting where dormancy is naturally cyclic across seasons. To do this we will exploit the Arabidopsis ecotypes Cvi and Bur, which have evolved different responses to environmental signals so they germinate at different times of the year. In addition these ecotypes have dramatically different flowering times with the combined effect that they have different life cycle patterns. Comparison of these two ecotypes is an excellent way to investigate the link between germination timing and flowering time to gain more understanding of different life cycle strategies, and this is the second aim of the proposed work. We will address these aims through the following objectives; 1. Identify differences in the expression patterns of key dormancy regulating genes across the cycle of seasons in ecotypes with different life cycle strategies. 2. Develop improved understanding of the regulation of, and link between, the timing of germination and flowering time. 3. Identify and investigate informative life cycle traits with a view to increased understanding of the potential for annual plants to adapt to climate change. Objectives 2 and 3 will be addressed through a quantitative genetic analysis of a new Recombinant Inbred Line (RIL) population between these two divergent ecotypes. This approach allows us to develop a genetic basis for these life cycle traits and therefore a way to understand and manipulate them. Using a thermogradient tunnel and selected RILs in objective 3 we also intend to conduct a unique and timely investigation of the impact of global warming on plant life cycle strategies and the potential to adapt through natural variation.

This projects aims are twofold, firstly to increase understanding of the regulation of Arabidopsis seed dormancy in a field setting where dormancy is naturally cyclic across seasons. To do this we will exploit the Arabidopsis ecotypes Cvi and Bur, which have evolved divergent regulation of seed dormancy in response to environmental signals. However, these ecotypes also have dramatically different flowering times, which make them ideal for investigating the link between germination timing and flowering time to dissect life cycle strategies within a single species, and this is the second aim of the proposed work. Objectives: 1. Identify differences in the expression patterns of key dormancy regulating genes across the cycle of seasons in the field using ecotypes with different life cycle strategies. 2. Develop improved understanding of the regulation of, and link between, the timing of germination and flowering time. 3. Identify and investigate informative life cycle traits with a view to increased understanding of the potential for annual plants to adapt to climate change. For objectives 2 and 3 we will adopt the following approach. We will identify important life cycle traits and ways of screening them in Arabidopsis. These screens will be applied to a new Recombinant Inbred Line (RIL) population we will construct between these two divergent ecotypes (Cvi x Bur) and subject the data to a quantitative genetic analysis. Under objective 3 we intend to use parents and selected RILs in a thermogradient tunnel apparatus to conduct a unique and timely investigation of the impact of global warming on plant life cycle strategies and the potential to adapt through natural variation. In the work proposed we intend to develop unique knowledge, in a field context, that is fundamental to understanding the competitive nature of weeds in crop production and the potential for climate change adaptation.

The proposed project aims to develop greater understanding of seed dormancy cycling by a combination of physiological, ecological and molecular work in the context of the life history of plants in the field environment. This novel approach taken by our group is already producing fresh insights in to the temporal integration and regulation of the hormone signalling pathways that control dormancy cycling. We therefore believe that the work proposed will have a major academic impact on the way seed dormancy is viewed by molecular biologists that are constrained to the laboratory environment. Our future aim is to use the understanding we are developing to inform the continued development of our germination models, in particular, our combined simulation of the germination and emergence of both crops and weeds (described briefly in Part 1A); this has significant applied value. For example, models produced in the Finch-Savage group have been used to develop general guidelines for the timing of cultural weed control practices in relation to crop sowing time (Defra Project 3406SX). Such cultural (non-herbicide) weed control practices are becoming of increasing importance for sustainable farming practices as the predicted herbicide-limited future of crop production develops due to consumer pressure and EU legislation. The understanding we will develop in this project complements directly our current more applied projects funded by Defra to 'understand the involvement of dormancy in the persistence and competitiveness of weeds in the Brassicaceae' (Defra project IF0116), and to develop understanding of 'life history variation in weed populations' (Defra project IF01103). Both these projects and the recommendations that come from them will benefit from the proposed work. Both projects are in support of developing weed control practices for sustainable farming systems and therefore directly relevant to Food Security a major priority area for BBSRC. Our approach of studying both Arabidopsis and related weeds and crops (BBSRC project BB/E006418/1, IPA with Syngenta) of the Brassicaceae is resulting in a significant contribution to translational biology (e.g. Finch-Savage et al. 2010 Plant Sci. Doi.10.1016/j.plantsci.2010.06.005) another BBSRC priority that has both academic and commercial impact; the latter through the involvement of seed/breeding companies. We believe the proposed work will provide significant insight into to how the life cycles of weeds and other annual plants will respond and adapt to global warming resulting from climate change. Understanding in this area is currently limited; we therefore expect this work to have significant impact in the BBSRC priority area of climate change. In addition, the new RIL population that we will construct will be deposited at the Nottingham Arabidopsis Resource Centre for the use by other researchers in this area. Dormancy is a major issue in the practical operation gene banks that store seeds for conservation. Seed dormancy is also a significant practical problem in establishing plants on reclamation sites hindering efforts to improve biodiversity. Improved understanding of dormancy will benefit both these approaches to preserving biodiversity. In addition to the normal routes of publication and presentations at scientific meetings the results of the proposed work will be widely disseminated as the Finch-Savage group are active participants in the seed science community with considerable experience in collaborating with other research groups, the training and mentoring of students, and in communicating with non-specialist audiences. W. F-S is currently President Elect of the International Society for Seed Science (ISSS) the principal 'professional society for promoting research, education and communication in the scientific understanding of seeds' to academics and the seed industry.