Lead


Lay summary
Flowering plants generally reproduce sexually, generating progeny through double fertilisation of the egg and central cell. Some flowering plants reproduce without sex employing an alternative, closely related, asexual reproductive strategy, known as apomixis. This deviation from sexual reproduction avoids meiosis (reductional division) and fertilisation and is thought to have evolved from the spatial and temporal deregulation of the sexual processes. More specifically (i) meiosis is circumvented (apomeiosis); (ii) the egg is activated without fertilisation (parthenogenesis); and (iii) functional endosperm is produced. These elements of apomixis are likely to depend on de-regulated gene expression in the nucellus (apomeiosis), the egg cell (parthenogenesis), and the central cell in apomicts that produce autonomous endosperm. Harnessing apomictic technology will permit the development of crop plants that allow agriculture to benefit from the indefinite fixation of hybrid vigour, since apomictic progeny are maternal clones.Experimentally, biological processes can be deregulated using mutagenic approaches, such as mis-expression, silencing or mutation. Since apomixis is a dominant trait, we will adopt a gain-of-function approach to deregulate gene expression in specific cell-types important for reproductive development. We will develop a two-component system that provides reliable, conditional gene activation.The early nucellus and egg cell will be targeted to mis-express tagged genes. An inducible chimeric transcription factor will be expressed in the either early nucellus or the egg cell. Randomly tagged genes will be transactivated in these tissues and plants screened for apomictic qualities. Apomeiotic mutants are likely to be either sterile or produce triploid (3n) progeny after fertilisation. Sterility is easily assayed and triploids can be identified using a simple flow cytometry screen. Parthenogenetic mutants will be isolated using a conditionally male sterile Arabidopsis line. Plants showing aspects of seed development under conditions favouring male sterility will identify genes that, when mis-expressed, produce parthenogenetic qualities.