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

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Summary

Introduction

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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