Abstract
Self-incompatibility affects not only the formation of seeds, but also the evolution of species diversity. A robust understanding of the molecular mechanisms of self-incompatibility is essential for breeding efforts, as well as conservation biology research. In recent years, phenotypic and multiple omics studies have revealed that self-incompatibility in Orchidaceae is mainly concentrated in the subfamily Epidendroideae, and the self-incompatibility phenotypes are diverse, even in the same genus, and hormones (auxin and ethylene), and new male and female determinants might be involved in SI response. This work provides a good foundation for future studies of the evolution and molecular mechanisms of self-incompatibility. We review recent research progress on self-incompatibility in orchids at the morphological, physiological, and molecular levels, provide a general overview of self-incompatibility in orchids, and propose future research directions.
Highlights
Self-incompatibility (SI) refers to the inability of hermaphroditic angiosperms to selfpollinate, which promotes outcrossing or hybridization [1]
SI is divided into two categories based on genetic characteristics: gametophytic self-incompatibility (GSI) and sporophytic self-incompatibility (SSI)
We focus on recent research progress on orchid at the morphologiorchids
Summary
Self-incompatibility (SI) refers to the inability of hermaphroditic angiosperms to selfpollinate, which promotes outcrossing or hybridization [1]. The growth of the pollen tube in more than half of the self-incompatible species stops in the style, and these species are distributed in different branches of Dendrobium phylogenetic tree [28,29], which is the main SI phenotype and consistent with the GSI phenotype. The diverse pollen germination and pollen tube growth phenotypes suggest that there might be more than one molecular mechanism of SI in Dendrobium species. The emergence times of the SI phenotypes after self-pollination varies from species to species, mostly at three to five days, but even at two to three weeks, which much longer than that (mostly from tens of minutes to hours [35,36]) in other angiosperm families with their molecular mechanisms known. Investigation of more other orchids SI species is needed, which may reveal more SI phenotypes
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