Antisense Oligodeoxynucleotide-Mediated Gene Knockdown in Pollen Tubes

Investigating vesicle-mediated regulation of pollen tube growth through BFA inhibition and AS-ODN targeting of TfRABA4D in Torenia fournieri

In flowering plants, pollen tube growth is essential for delivering immotile sperm cells during double fertilization, directly influencing seed yield. This process relies on vesicle-mediated trafficking to sustain tip growth and fertility. However, investigating pollen tube growth is challenging in non-model plants due to the lack of transgenic tools. Here, we developed a method to transiently inhibit vesicle activity in pollen tubes of the wishbone flower (Torenia fournieri), a classic plant for sexual reproduction studies, using brefeldin A (BFA) and antisense oligodeoxynucleotides (AS-ODNs) targeting key genes. BFA broadly disrupted vesicle gradient homeostasis in T. fournieri pollen tubes, leading to widespread changes in cell wall deposition, ROS distribution, and pollen tube morphology. To assess the role of specific genes, we designed AS-ODNs against TfANX, the sole ANXUR homolog in T. fournieri, which successfully penetrated cell membranes and suppressed TfANX expression. This inhibition impaired pollen tube tip growth, causing pollen tube leakage at the shank region and, in some cases, multiple leakages. Similarly, AS-ODN targeting TfRABA4D, a pollen-specific vesicle regulator, induced a bulging phenotype and disrupted pectin deposition and reduced ROS distribution, mirroring BFA effects. These findings elucidate vesicle-mediated regulation in pollen tube tip growth and introduce an accessible method for genetic manipulation in reproductive research of non-model plants.

Regulation of Exocyst Function in Pollen Tube Growth by Phosphorylation of Exocyst Subunit EXO70C2

Exocyst is a heterooctameric protein complex crucial for the tethering of secretory vesicles to the plasma membrane during exocytosis. Compared to other eukaryotes, exocyst subunit EXO70 is represented by many isoforms in land plants whose cell biological and biological roles, as well as modes of regulation remain largely unknown. Here, we present data on the phospho-regulation of exocyst isoform EXO70C2, which we previously identified as a putative negative regulator of exocyst function in pollen tube growth. A comprehensive phosphoproteomic analysis revealed phosphorylation of EXO70C2 at multiple sites. We have now performed localization and functional studies of phospho-dead and phospho-mimetic variants of Arabidopsis EXO70C2 in transiently transformed tobacco pollen tubes and stably transformed Arabidopsis wild type and exo70C2 mutant plants. Our data reveal a dose-dependent effect of AtEXO70C2 overexpression on pollen tube growth rate and cellular architecture. We show that changes of the AtEXO70C2 phosphorylation status lead to distinct outcomes in wild type and exo70c2 mutant cells, suggesting a complex regulatory pattern. On the other side, phosphorylation does not affect the cytoplasmic localization of AtEXO70C2 or its interaction with putative secretion inhibitor ROH1 in the yeast two-hybrid system.