Abstract
We have recently characterised NET2A as a pollen-specific actin-binding protein that binds F-actin at the plasma membrane of growing pollen tubes. However, the role of NET2 proteins in pollen development and fertilisation have yet to be elucidated. To further characterise the role of Arabidopsis NET2 proteins in pollen development and fertilisation, we analysed the subcellular localisation of NET2A over the course of pollen grain development and investigated the role of the NET2 family using net2 loss-of-function mutants. We observed NET2A to localise to the F-actin cytoskeleton in developing pollen grains as it underwent striking structural reorganisations at specific stages of development and during germination and pollen tube growth. Furthermore, net2 loss-of-function mutants exhibited striking morphological defects in the early stages of pollen tube growth, arising from frequent changes to pollen tube growth trajectory. We observed defects in the cortical actin cytoskeleton and actin-driven subcellular processes in net2 mutant pollen tubes. We demonstrate that NET2 proteins are essential for normal actin-driven pollen development highlighting an important role for the NET2 family members in regulating pollen tube growth during fertilisation.
Highlights
The male reproductive cycle of angiosperms is an elaborate process, comprising the development and generation of highly specialised pollen grain cells within the anther locule; a process known as microgametogenesis
Actin is implicated in regulating specific reorganisations of cellular structure that occur in developing pollen, including fragmentation and dispersal of the pollen vacuole, and structuring of the plasma membrane, both of which are dependent on clathrinmediated endocytosis (CME; Kang et al, 2003; Yamamoto et al, 2003; Kim et al, 2013)
We demonstrated that NETWORKED 2A (NET2A) bound F-actin to the plasma membrane through interaction with the membrane-integral receptors, POLLEN RECEPTOR-LIKE KINASEs 4 and 5 (PRK4 and PRK5), to form physical links between the actin cytoskeleton and plasma membrane, so-called ‘actin-membrane contact sites’ (AMCSs; Duckney et al, 2017)
Summary
The male reproductive cycle of angiosperms is an elaborate process, comprising the development and generation of highly specialised pollen grain cells within the anther locule; a process known as microgametogenesis. The actin cytoskeleton is crucial for pollen development, germination and pollen tube growth (Gervais et al, 1994; Zonia et al, 1999; Gibbon et al, 1999; Vidali et al, 2001). During microgametogenesis actin regulates some processes including nuclear migration, mitotic divisions and cell expansion. Actin is implicated in regulating specific reorganisations of cellular structure that occur in developing pollen, including fragmentation and dispersal of the pollen vacuole, and structuring of the plasma membrane, both of which are dependent on clathrinmediated endocytosis (CME; Kang et al, 2003; Yamamoto et al, 2003; Kim et al, 2013). In pollen germination and tube growth, actin regulates targeting of Golgi-derived secretory vesicles to the growing tip, cytoplasmic streaming and endocytosis
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
