RECBREED

Recombination: an old and new tool for plant breeding

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 Obiettivo del progetto (Objective)

'Successful and efficient plant breeding depends on rapid recombination of advantageous traits to form new crop varieties. In recent years new breeding techniques have been introduced which rely on transgenic alteration of somatic cells and regeneration into plants with novel properties. The precision and effectiveness of both strategies rely upon homologous recombination (HR). The objective of this proposal is to provide plant breeders with new tools allowing better control over HR in both somatic and meiotic cells. The expected outcomes of the proposed research are efficient gene targeting (GT) technologies for precise engineering of plant genomes and control of rates of meiotic recombination between homologous or homeologous chromosomes in classical breeding. The major components of the HR machinery are common to somatic and meiotic cells, enabling us to address both processes in a synergistic way. HR can be divided into different steps: initiation by formation of a DNA double-strand break (DSB); recognition and invasion of an homologous DNA sequence; resolution of recombination structures. Each stage contains a bottleneck for both GT and meiotic HR that we will address. Work package 1 (WP1) aims at enhancing HR through targeted DSB induction. DSBs will be induced by Zinc-finger nucleases that can be custom-designed for target sequences anywhere in the genome. In WP2, we will test the influence of HR factors affecting homologue invasion and heteroduplex formation, such as RAD51 and its paralogues, the RAD52 homologue, genes that affect cytosine methylation in DNA, and mismatch repair. In WP3 we will concentrate on proteins involved in resolution and crossing-over. WP4 will test combinations of those approaches found in the first three WPs to build optimal strategies for application. Most experiments will be performed in the model plant Arabidopsis and implemented into crops such as tomato and maize to guarantee quick applicability for breeding.'

Introduzione (Teaser)

Rising population numbers have raised the demand for food, clothing and other necessities. EU funding is helping to breed plants with desirable traits such as improved fungi resistance, drought resistance and high yield to meet these growing needs.

Descrizione progetto (Article)

The EU-funded project 'Recombination: An old and new tool for plant breeding' (http://recbreed.eu/ (RECBREED)) was initiated to realise the development of 'super' plants. The RECBREED consortium worked on optimising plant breeding by developing a better toolkit to produce plants with desirable traits and weed out undesirable traits.

They explored different homologous recombination (HR) techniques enables the exchange of genetic material for purposes of DNA repair, reproduction (also called meiosis) and artificial gene transfer between different species or strains. Techniques included gene targeting (GT), meiotic recombination and DNA double-stranded break induction (DSB) by artificial nucleases.

RECBREED achieved several milestones in the accurate engineering of plant genomes. Each stage in HR was studied in depth by characterising important genes and elucidating their function using selected crops such as tomato, maize and Arabidopsis. Suitable molecular markers were identified through bioinformatics analyses and used for testing and validation.

Scientists successfully performed DSB-induced mutagenesis and GT in Arabidopsis and tomato using zinc finger nucelases and transcription activator-like effector nucleases. No toxic or negative plant growth effects were observed with either of these methods. An innovative GT method called in planta was developed that separates the transformation and GT steps, and its efficacy was demonstrated in maize and Arabidopsis. Another key achievement was a 10-fold increase in precise GT rate achieved by enhancing GT frequencies through over-expression of the protein AtRAD52-1A.

Particular emphasis was placed on understanding and modulating factors affecting meiotic recombination. Key parameters such as Rad51 paralog proteins, DNA methylation states, chromatin structure and recombinases (Rad51 and Dmc1) were successfully identified.

Conventional agricultural techniques have been proven inadequate when it comes to meeting the rapidly growing demands for food and feed. Use of GT technology could prove to be viable for industrial production of superior high-yield, high-nutrition plants. This has important socioeconomic implications for the European agricultural sector with a current market share of about EUR 4 000 million in seed sales alone. Combining agriculture with biotechnology will only serve to further strengthen the EU position in this arena.