Dying with Style: Death Decision in Plant Embryogenesis

Abstract

Embryogenesis is a fascinating event during the plant life cycle encompassing several steps whereby the zygote develops into a fully developed embryo which, in angiosperms, is composed of an axis separating the apical meristems, and two cotyledons. Recapitulation of embryogenesis can also occur in vitro through somatic embryogenesis, where somatic cells are induced to form embryos, and androgenesis, in which embryos originate from immature male gametophytes. Besides cell division and differentiation, embryo patterning in vivo and in vitro requires the dismantling and selective elimination of cells and tissues via programmed cell death (PCD). While the manifestation of the death program has long been acknowledged in vivo, especially in relation to the elimination of the suspensor during the late phases of embryo development, PCD during in vitro embryogenesis has only been described in more recent years. Independent studies using the gymnosperm Norway spruce and the angiosperm maize have shown that the death program is crucial for the proper formation and further development of immature somatic embryos. This chapter summarizes the recent advances in the field of PCD during embryogenesis and proposes novel regulatory mechanisms activating the death program in plants.

Suppression of Metacaspase- and Autophagy-Dependent Cell Death Improves Stress-Induced Microspore Embryogenesis in Brassica napus

“…Since the mechanisms that control microspore reprogramming upon exposure to stress are not yet fully understood, efficient protocols for microspore embryogenesis are not available for many species of agronomic interest that show recalcitrant responses to stress treatment. In particular, increased cell death is a common stress response shared by all microspore embryogenesis in vitro systems, that impairs developmental reprogramming process leading to decreased embryo yield (Satpute et al, 2005;Rodríguez-Serrano et al, 2012;Huang et al, 2016;Bárány et al, 2018;Berenguer et al, 2019). Understanding the mechanisms controlling cell death in microspore cultures will help to identify new targets for improving biotechnological methods.…”

Morpho‐histology of co‐occurrence of somatic embryos, shoots, and inflorescences within a callus of Limonium ‘Misty Blue’

“…The dying of neighboring cells accomplished successful somatic embryo and shoot bud development. These neighboring cells probably supplied nutrients and other extracellular materials to the cells of the embryo proper at the initial stage of growth, as reported byHuang et al (2016). The significance of PCD during two phases of somatic embryo development, i.e., the conversion from proembryogenic masses to somatic embryos and correct pattern formation in Picea abies, was clearly demonstrated byFilonova et al (2000).…”

Redirecting Cell Fate During in vitro Embryogenesis: Phytoglobins as Molecular Switches

“…Together with stress, plant growth regulators, especially auxin, have been linked to the somatic-embryogenic transition. Inclusion of different types of auxins in the culture medium is routinely used to trigger cellular dedifferentiation in both gymnosperms and angiosperms (Huang et al, 2016 ). An often cited example on the requirement of auxin for this event is the carrot culture system where embryo development from single cells is initiated by addition of the synthetic auxin 2,4-D (Nomura et al, 1995 ).…”

“…Together with division and differentiation, PCD is a conserved developmental process manifested during plant embryogenesis and required to dismantle the suspensor and degrade subordinate embryos in gymnosperms seeds (review in Huang et al, 2016 ). Execution of PCD is also an integral component of in vitro embryogenesis and was first described in spruce (Filonova et al, 2002 ).…”