Regulation of the male germline in cereal crops by somatic companion cells

Like animals, most diploid plants reproduce sexually after going through genetic reduction (meiosis) to produce specialized haploid gametes (i.e. sperm cells and egg cells) within the male and female sex organs, respectively. However, the process by which plants establish haploid sexual lineages (or germlines) from diploid somatic tissues late in adult life is not yet understood, but is thought to involve large-scale developmental and whole-genome reprogramming. This proposal focuses on uncovering some of the mechanisms involved in this process. We have evidence that novel small-RNA binding Argonaute proteins (AGOs) specifically found in male reproductive organs of cereals and their associated class of small non-coding RNA molecules control the development of the male germline. Intriguingly, these AGOs are expressed in somatic cells surrounding the male germline and sperm cells, yet defects or mutations in these AGOs causes male sterility. In this proposal, we will use various approaches and experimental techniques (eg. developmental genetics, biochemistry, computational and molecular biology) to determine exactly how somatic companion cells regulate the fate of the male germline using two important model crop plants: maize and wheat. We anticipate that this work will not only advance our basic understanding of how plants set their male germline, but will also provide a novel strategy to engineer new breeding tools in agronomically important cereal crops.

Sexually reproducing organisms must undergo meiosis to generate distinct male and female germlines. Recent studies in animals have shown that genetic and epigenetic factors regulate the development of the germline, however, research is lagging in plants, and many of the key players and precise mechanisms remain elusive. This proposal aims to investigate how neighbouring somatic cells can regulate male germline development and gametogenesis in maize through action of a novel Argonaute protein (named MAGO) and associated new class of small non-coding RNAs found only in monocots. This proposal specifically focuses on revealing the following key objectives:
1. The role of MAGO during male meiosis and gametogenesis.
2. The biochemical and molecular nature of MAGO action in maize somatic germline companion cells.
3. Defining the role of MAGO-associated non-coding RNAs during male germline development.
4. To test the functional conservation of this fundamental pathway in wheat to engineer new breeding approaches.
This work will advance our basic understanding of how cereal crops set the male germline and provide essential know-how for creating novel strategies and breeding tools in cereal crops.

Data and material generated from this proposal will be made freely available. In addition, the University of Warwick, will exploit IP generated through other aspects of the work. We will engage with industrial beneficiaries to the develop novel approaches for the improvement of maize and wheat traits through existing collaborations with two agro-biotechnology partners.
We will disseminate our findings by making our data publicly available through peer-reviewed publication. The resources will be deposited at EMBL-EBI, NCBI and Maize Genetic COOP Stock Center. Training in scientific research skills will be provided to the RPDA and RA by the PI, colleagues at the University of Warwick and NIAB, and by existing collaborations with international scientists. We will disseminate our results to the public through media reports and by interacting directly with plant breeders and plant biotechnology industries through NIAB Innovation Farm events. Pathways to impact will be monitored and evaluated every six months to ensure efficient dissemination of information.