Localization of Arabidopsis SYP125 syntaxin in the plasma membrane sub-apical and distal zones of growing pollen tubes

Abstract

Tip growth in pollen tubes occurs by continuous vesicle secretion and delivery of new wall material, but the exact sub-cellular location of endocytic and exocytic domains remains unclear. Here we studied the localization of the Arabidopsis thaliana pollen specific syntaxin SYP125 using GFP-fusion constructs expressed in Nicotiana tobaccum pollen tubes. In agreement with the predicted role for syntaxins, SYP125 was found to be associated with the plasma membrane and apical vesicles in growing cells. At the plasma membrane, SYP125 was asymmetrically localized with a higher labeling 20-35 μm behind the apex, a distribution which is distinct from SYP124, another pollen-specific syntaxin. Competition with a related dominant negative mutant affected the specific distribution of SYP125 but not tip growth. Co-expression of the phosphatidylinositol-4-monophosphate-5-kinase 4 (PIP5K4) or of the small GTPase Rab11 perturbed polarity and the normal distribution of GFP-SYP but did not inhibit the accumulation in vesicles or at the plasma membrane. Taken together, our results corroborates previous observations that in normal growing pollen tubes, the asymmetric distribution of syntaxins helps to define exocytic sub-domains but requires the involvement of additional signaling and functional mechanisms, namely phosphoinositides and small GTPases. The localization of syntaxins at different membrane domains likely depends on the interaction with specific partners not yet identified.

A role for diacylglycerol kinase 4 in signalling crosstalk during Arabidopsis pollen tube growth

“…affecting actin dynamics and secretion) and ultimately conditioning the perception and response to extracellular guidance cues. The fluctuations reported here in the DGK4 localization in the apical and subapical region might reflect just this, and we have previously observed dynamic positioning of other proteins in the apical and subapical region upon changes in growth rate and directioning: PIP5K4 (Sousa et al ., ), syntaxin SYP125 (Ul‐Rehman et al ., ) and CNGC7 (Tunc‐Ozdemir et al ., ). This would also help to explain the natural variability in pollen tube responses to imposed extracellular stimuli and strengthens the concept that guidance is dependent on a network of signalling and structural elements that interpret extracellular cues while maintaining homeostasis.…”

Ion and lipid signaling in apical growth—a dynamic machinery responding to extracellular cues

“…(B) Tobacco pollen tubes expressing SYP124-GFP (upper image), SYP125-GFP (middle image), and co-expressing both constructs (lower image; SYP124 signal in red and SYP125 signal in green). For methods see Ul-Rehman et al (2011) . Bar = 10 μm.…”

Cold stress alters transcription in meiotic anthers of cold tolerant chickpea (Cicer arietinum L.)

“…It might be possible that the genes for intracellular protein transport (SYP124, vesicular mediated transport) and fatty acid transport (peroxisomal ABC transporter) UP in the cold-treated anthers, fulfill this requirement. It is already established that the peroxisomal ABC transporter plays role in pollen maturation, pollen exine formation and pollen tube growth [ 32 , 33 ] whereas SYP124 in pollen tube growth [ 39 ]. Another gene, WAX2 is required for fertility and seed formation in Arabidopsis [ 40 ].…”