Syntaxin of plants31 (SYP31) and SYP32 is essential for Golgi morphology maintenance and pollen development

Abstract

Pollen development is a key process for the sexual reproduction of angiosperms. The Golgi plays critical roles in pollen development via the synthesis and transport of cell wall materials. However, little is known about the molecular mechanisms underlying the maintenance of Golgi integrity in plants. In Arabidopsis thaliana, syntaxin of plants (SYP) 3 family proteins SYP31 and SYP32 are the only two Golgi-localized Qa-soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNAREs) with unknown endogenous functions. Here, we demonstrate the roles of SYP31 and SYP32 in modulating Golgi morphology and pollen development. Two independent lines of syp31/+ syp32/+ double mutants were male gametophytic lethal; the zero transmission rate of syp31 syp32 mutations was restored to largely normal levels by pSYP32:SYP32 but not pSYP32:SYP31 transgenes, indicating their functional differences in pollen development. The initial arrest of syp31 syp32 pollen occurred during the transition from the microspore to the bicellular stage, where cell plate formation in pollen mitosis I (PMI) and deposition of intine were abnormal. In syp31 syp32 pollen, the number and length of Golgi cisterna were significantly reduced, accompanied by many surrounding vesicles, which could be largely attributed to defects in anterograde and retrograde trafficking routes. SYP31 and SYP32 directly interacted with COG3, a subunit of the conserved oligomeric Golgi (COG) complex, and were responsible for its Golgi localization, providing an underlying mechanism for SYP31/32 function in intra-Golgi trafficking. We propose that SYP31 and SYP32 play partially redundant roles in pollen development by modulating protein trafficking and Golgi structure.

SEC1A is a major Arabidopsis Sec1/Munc18 gene in vesicle trafficking during pollen tube tip growth

“…SM proteins promote membrane fusion by regulating SNARE complex assembly through the binding of Qa‐SNAREs or assembling trans ‐SNARE complexes (Baker & Hughson, 2016; Risselada & Mayer, 2020). Several SNARE proteins with functions in pollen have been identified (Sanderfoot et al., 2001; Slane et al., 2017; Sogawa et al., 2020; Rui et al., 2021). Of particular interest here are three Qa‐SNAREs of the SYP family (SYP124, SYP125 and SYP131), which are all exclusively expressed in male gametophytes (Silva et al., 2010; Ichikawa et al., 2015; Slane et al., 2017).…”

Endosomally Localized RGLG-Type E3 RING-Finger Ligases Modulate Sorting of Ubiquitylation-Mimic PIN2

“…To learn about the subcellular localization of RGLG1:Venus signals in more detail, we made use of selected Wave marker lines [ 19 ], which we combined with RGLG1::RGLG1:Venus by crossing. A pronounced co-localization was observed between RGLG1:Venus and tagged Golgi structures-localized SYNTAXIN OF PLANTS 32 (SYP32:mCherry) [ 20 ] ( Figure 2 A). In addition, RGLG1:Venus shows co-localization with the presumptive secretory/recycling endosome marker RabA5d:mCherry ( Figure 2 B) and with late endosome/PVC marker RabF2b/ARA7:mCherry ( Figure 2 C).…”

SNAREs Regulate Vesicle Trafficking During Root Growth and Development

“…In pollen with syp31 syp32 double mutations, secretion of JIM7 (labeled highly methylesterified pectins)-positive vesicles from the Golgi/trans-Golgi network into the ectoplasm is blocked. Partial loss of the association of the endomembrane protein12 (EMP12) with the Golgi apparatus in syp31 syp32 double mutations pollen ( Gao et al, 2012 ; Li et al, 2019 ; Rui et al, 2021 ). Furthermore, mCherry-HDEL trafficking between the ER and Golgi was disrupted, and it was mistargeted to vacuoles.…”

“…Furthermore, mCherry-HDEL trafficking between the ER and Golgi was disrupted, and it was mistargeted to vacuoles. SYP31 and SYP32 interact directly with conserved oligomeric Golgi 3 (COG3), which is a subunit of the COG complex and is responsible for its Golgi localization, indicating a role of SYP31/32 in intra-Golgi trafficking ( Tan et al, 2016 ; Rui et al, 2021 ). Qc-SNARE BET12 localizes to both the Golgi and TGN, and it is involved in protein transport in the early secretory pathway.…”