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Meiotic Control of Recombination in Crops

Periodic Reporting for period 2 - MEICOM (Meiotic Control of Recombination in Crops)

Reporting period: 2020-01-01 to 2022-06-30

MEICOM was designed to achieve a better understanding of the factors that influence the transitions from DNA double strand breaks (DSBs) formation to meiotic crossovers (COs) in crops and evaluate the most effective methodologies to manipulate this outcome. Crop breeding is necessary to deliver Food Security in the near future, factors such as population growth, urban and industrial development, mass migration and climate change would require a sustained improvement in food production, storage and distribution globally. Crop breeding has a very important role to play in provide these improvements. Crop breeding methods rely on meiotic recombination to generate genetic variation through the formation of COs to produce plants with new genetic combinations to provide new improved crop varieties ready to withstand our changing environment challenges of the future. Nevertheless, meiotic recombination has natural major limitations that plant breeders need to overcome. The main ones are that CO frequency is limited in number (1-3 COs per chromosome pair) and CO localization is restricted to some chromosome regions (with up to 70% of the physical length of individual chromosomes rarely recombining in cereals). If we are able to determine the different factors that regulate CO frequency and localization in crops and evaluate different strategies to manipulate this regulation, we would be able to provide plant breeders with new tools and methodologies to improve crop breeding in the new decades.
To achieve this ambitious goal we assembled a network of leading European plant meiosis research groups (MEICOM) with a wide range of complementary research skills and excellent track record of synergistic interactions. The training also has benefited from close involvement of stakeholder breeding companies who have provided first-hand insight into the major challenges that confront the industry. Importantly, MEICOM has provided a major contribution to ensuring a critical mass of highly trained early career scientists with skills that will be required to tackle the global challenge of Food Security. The overall objectives were: to understand the influence of the genomic environment on crossover formation/control in crops and evaluate how it can be modified to adjust the crossover/non-crossover outcome, to study how meiotic progression in large genome crops is integrated with, and influences the crossover/non-crossover repair fate of DNA double-strand breaks, and to develop and implement novel strategies for modifying crossover patterning in target crops. Results have been very important to realize the differences in the control of meiotic recombination among the different crop species (and specially the model plant Arabidopsis thaliana). Another important result is the possibility of Genome-wide high-throughput pollen genotyping in cereals and the chance to be applied to other crops. Different groups in the network have set up different methods to apply chemicals to gonads which can manipulate the outcomes of meiosis in different crops (e.g.: barley, tomato, brassicas).
This project has been designed with three complementary experimental Work Packages (WPs): WP1: Interplay between the genomic environment and CO formation. WP2: Integration of DSB repair fate and meiotic progression in crops. WP3: Developing and implementing methods that modify recombination patterning. Since the beginning of the project the milestones and deliverables were achieved at the correct time. Obviously, at the beginning of 2020, with the Covid-19 pandemic and the different restrictions imposed nationally and internationally, the different projects were halted. The delivery times had to be postponed but all of them were carried out thanks to different extensions provided by the different institutions for the ESRs to achieve their goals. Delivery meetings and conferences had to be done online but resulted in great success among the ESRs who adapted marvellously to the new circumstances. A proof of it are the different International Conferences that the ESRs have been participating online during that period of time (2020-2022).
The network has achieved several publications in international journals (included Science, PLoS Genetics, etc). 11 students have achieved their doctorates with only one withdrawing in early 2019 due to health issues. The ESRs have participated with posters and oral presentations in face to face International Conferences before Covid-19 Restrictions and on line conferences during the Covid-19 restrictions as well as seminars in their different institutions. The ESRs have been very prolific on outreach events again face to face (University Open Days, GENIE’s Dynamic DNA Leicester 2018, MEICOM Meet the Scientist Think Tank Museum Birmingham 2019). Furthermore, ESR4 designed and conducted a survey in which she asked 23 private sector researchers and 47 public sector researchers on their opinions and perspectives regarding the manipulation of meiotic behavior in plant breeding.
MEICOM has showed how the control of meiotic recombination can diverge in different plant species, especially in crops. This is a very important issue for plant breeders who will need to acknoledge these differences and apply different tools to achieve their breeding goals to manipulate meiotic recombination in different crop species. We have analyzed different crops in this network with different agriculture interests and in several instances we have been found differences with what we thought it was a standard plant model (Arabidopsis) for meiotic recombination in plants.
The different chemical applications techniques to manipulate meiosis in different crops achieved in this project would open new methods and tools for plant breeders which might try to move the localization of recombination along the chromosomes to obtain different trait mixes that might have been impossible to obtain until now. Live imaging of meiosis in maize has been achieved in order to study in more precision the different chromosome and chromatin changes during meiotic recombination. Chromosome axis and synaptonemal complex proteins have been analysed in barley, brassicas and wheat, showing some interesting differences among crops and Arabidopsis mutants in these components. Furthermore, the use of CRISPR/Cas9 technology and recombinant constructs with enzymes involved in DSBs formation have shown limitations of these techniques on tomato, brassica and even in Arabidopsis. The results are pointing into a very specific and complex iteration of Spo11 proteins and other components on DSB formation that can be seriously affected by producing recombinant proteins with genome editing systems like CRISPR/Cas9.
The ESRs have participated in different conferences and disseminate their results on several publications to the scientific community. Due to Covid-19 restrictions some of the meetings to disseminate our science to a broadly audience were not possible. Nevertherless, we were able to hold an important outreach dissemination activity at the Think Tank Museum where we were able to explain our science to a broader audience. Furthermore, MEICOM coordinator presented “Using chromosomes to ensure food security” at a Pint of Science event “our future World at The Exchange. This outreach presentation included major topics and achievements from MEICOM.
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Image Used on PintofScience dissemination by Coordinator at Bham