Abstract
The development of male and female gametophytes is a pre-requisite for successful reproduction of angiosperms. Factors mediating vesicular trafficking are among the key regulators controlling gametophytic development. Fusion between vesicles and target membranes requires the assembly of a fusogenic soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNAREs) complex, whose disassembly in turn ensures the recycle of individual SNARE components. The disassembly of post-fusion SNARE complexes is controlled by the AAA+ ATPase N-ethylmaleimide-sensitive factor (Sec18/NSF) and soluble NSF attachment protein (Sec17/α-SNAP) in yeast and metazoans. Although non-canonical α-SNAPs have been functionally characterized in soybeans, the biological function of canonical α-SNAPs has yet to be demonstrated in plants. We report here that the canonical α-SNAP in Arabidopsis is essential for male and female gametophytic development. Functional loss of the canonical α-SNAP in Arabidopsis results in gametophytic lethality by arresting the first mitosis during gametogenesis. We further show that Arabidopsis α-SNAP encodes two isoforms due to alternative splicing. Both isoforms interact with the Arabidopsis homolog of NSF whereas have distinct subcellular localizations. The presence of similar alternative splicing of human α-SNAP indicates that functional distinction of two α-SNAP isoforms is evolutionarily conserved.
Highlights
The development of male and female gametophytes is a pre-requisite for successful reproduction of angiosperms
Fusion between vesicle and target membranes is mediated by tetrameric sensitive factor attachment protein receptors (SNAREs) complexes, whose disassembly ensures the recycle of individual SNARE components
The disassembly of postfusion SNARE complexes is controlled by NSF/Sec18 and α-SNAP/Sec17 both in yeast and metazoans
Summary
The development of male and female gametophytes is a pre-requisite for successful reproduction of angiosperms. Megagametogenesis [1] and microgametogenesis [2, 3] produce female and male gametophytes, respectively. Meiosis of a megaspore mother cell produces four megaspores, among which only one survives as functional megaspore (FM). Meiosis of a microspore mother cell gives rise to a tetrad of microspores. After being released from the tetrad, each microspore goes through an asymmetric cell division, referred to as pollen mitosis I (PMI), to produce a bicellular microspore containing a generative cell and a vegetative nucleus. The generative cell undergoes another mitotic event, called pollen mitosis II (PMII), to produce two sperm cells enclosed in pollen together with the vegetative nucleus [2, 3]
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