Abstract
Reproductive biology varies between plants. Some plants can inbreed (self-fertilise) while others must outcross for successful reproduction. Manipulation of a plants ability to inbreed or outcross is important in improving efficiency in many crop breeding programs. Inbreeding is useful to fix desirable or purge deleterious traits, while both inbreeding and outcrossing are required for breeding F1 hybrid crops which benefit from heterosis. This research project centres around two different mechanisms by which fertility is manipulated in plants: male sterility systems and self-incompatibility systems.
Male sterility is when a plant is unable to produce viable pollen. Current male sterility systems have been proven to have varying efficiency and other limitations. Therefore, the first goal of this research is to restore fertility to transgenic male-sterile A. thaliana in order to help develop a reversible, dominant, male sterility system. Such a system will enable more efficient generation of F1 hybrid seed and stable biocontainment of genetically modified crops or weed species.
This research showed that male sterility induced by a dominant sterility gene, an artificial microRNA targeting the essential tapetal gene AMS, could be restored by introduction of a mutated version of the AMS gene in A. thaliana. However, restoration of fertility was not consistent. It was also observed that introduction of the mutated AMS gene was capable of inducing male sterility in A. thaliana, likely by increasing levels of the AMS protein and causing a loss of synchronisation between tapetal and microspore development.
Self-incompatibility is a trait which causes self-fertilisation to be inhibited, resulting from molecular interaction between male and the female components of the same plant. The second goal of this research is to test whether the protein DUF247 is the female component of the S-locus in the perennial ryegrass self-incompatibility system by investigating tissue specific expression, subcellular localisation, and protein-protein interactions. Since this research began it has been revealed that there are likely three components at the S-locus in grasses and that two of these components are DUF247 genes and the third is a gene referred to as SP. Both DUF247 and SP appear to be expressed in the ryegrass stigma, however, more work is required to determine what interaction may be occurring to give rise to self-incompatibility. Characterising the genes involved in the ryegrass SI reaction will provide opportunities to manipulate SI for more efficient ryegrass breeding and for generation of F1 hybrids.