Soybean androgenesis II: non-gametophytic morphologies in isolated microspore culture

Gametophytic embryogenesis is a process capable of accelerating trait discovery and cultivar development in plant-breeding programs. However, recalcitrance to morphogenic stimuli has limited such work in many crops of interest, especially among fabaceous species such as soybean ( Glycine max [L.] Merrill). In complementary studies, donor plant and culture conditions were documented to successfully divert isolated soybean microspores from a gametophytic pathway; these findings were reinforced through transcriptomic analysis of microspores subjected to pretreatment temperature stress, suggesting cellular dedifferentiation through suppression of the pollen developmental program. In the present study, cytological characteristics were observed in isolated microspore culture, which evidenced non-gametophytic development. These phenotypes included (i) inhibition of daughter cell specialization, (ii) pollen dimorphism, and (iii) exine rupture, among others. The outlined morphologies were placed into the context of established gametophytic embryogenesis platforms, further supporting previous claims of cell fate redirection in soybean microspores. The present study provides insight into gametophytic embryogenesis induction via isolated microspore culture and may prove useful for the investigation of soybean androgenesis.