Basis of apomixis in flowering plants – state of the art and research perspectives

In most angiosperm plants, seeds are produced through a sexual process. Some angiosperms have developed an alternative reproductive strategy termed apomixis which involves producing seeds without the key steps of sexual development (i.e. meiosis, fertilization) and results in progeny genetically identical to the mother plant. Despite significant research advances, the evolutionary origin and molecular nature of apomixis remain unclear. Recent findings suggest that apomixis may have emerged from a sexual pathway deregulated by genetic and epigenetic modifications and stress signals (both endogenous and exogenous) that led to the alteration or omission of selected stages of sexual development. Apomixis, as a natural phenomenon that enables clonal reproduction by seeds, is a desirable trait with great potential in plant breeding, especially in terms of preserving hybrid vigor and gene combinations of elite phenotypes over subsequent generations. Notwithstanding, apomixis does not occur in major crops and therefore research programs focus on how to introgress, induce, or mimic apomixis in agronomically significant sexual species. The present review outlines the history of research on apomixis in flowering plants, its mechanisms, and a summary of the latest and most impactful research advances that may pave the way for the introduction of apomixis to sexually reproducing crops. The reader's attention is also drawn to the partially explained issue of intercellular communication in ovules during early apomictic processes in the context of the cell wall's changed chemical composition in cells that enter the apomictic developmental pathway.