Growth and cellular organization of Arabidopsis pollen tubes in vitro

Abstract

Tricellular pollen tubes of Arabidopsis thaliana were cultured in vitro on solid media and studied with respect to growth, cellular organization and ultrastructure, cytoskeletal organization, organelle movement, deposition and structure of the wall and the occurrence of coated pits, all elements assumed to be relevant for tip growth. For our ultrastructural studies we used freeze fixation and freeze substitution. Although Arabidopsis pollen tubes are broadly similar to those of bicellular species such as Nicotiana tabacum and Lilium spec. and in vivo grown pollen tubes of Arabidopsis, some differences occurred. The density of the equally distributed, relatively small (85 nm) secretory vesicles (SV) in the tip is low (five/µm 2 ). In between the SV of the tip, membranous material, possibly smooth endoplasmic reticulum, fragments of rough endoplasmic reticulum and loose ribosomes are present. The wall in the tip is not amorphous but layered and a secondary wall is formed already in the flanks of the tip. The general pattern of organelle motion is reverse fountain-like, but individual organelles move in distinct lanes at speeds of up to 2 µm/s, and about half of the organelle population shows a moderate velocity or Brownian movement. These properties are discussed in relation to the low growth rate (10 µm/h) of Arabidopsis pollen grown in vitro. The two similar sperm cells are closely attached and are always found near the vegetative nucleus. No surrounding wall and no cytoskeletal elements were obvious in the sperm cells. The preferential location of the mitochondria at the wall and the large (up to 400 nm) coated pits are unique for angiosperm pollen tubes. The size of the coated pits may allow not only membrane retrieval but also pinocytosis.

γ-Tubulin Is Essential for Microtubule Organization and Development inArabidopsis

“…The pollen was viewed by UV epiillumination using a Leica DMRB microscope. Pollen germination tests were performed as described (Derksen et al, 2002).…”

SETH1andSETH2, Two Components of the Glycosylphosphatidylinositol Anchor Biosynthetic Pathway, Are Required for Pollen Germination and Tube Growth in Arabidopsis [W]

“…Individual open flowers were collected in microtiter plates (TC microwell 96F; Nucleon Biosciences, Glasgow, Scotland) containing 50 L of germination medium (Derksen et al, 2002) per well. Plates were sealed and incubated overnight at 22ЊC under continuous light.…”

Analysis of Transposon Insertion Mutants Highlights the Diversity of Mechanisms Underlying Male Progamic Development in Arabidopsis

“…Despite such postpollination (progamic) development, which inadvances, progress toward demonstrating their funcvolves rapid directional pollen tube growth within the tional roles is still limited. Reverse genetic approaches female reproductive tissues (reviewed in Pruitt 1999; have shown that pollen germination and tube growth Johnson and Preuss 2002;Lord 2003). Although postdepend upon the gametophytic synthesis of cellular pollination events have been extensively described at components involved in various signaling networks the cellular level, the identification and characterization (Muschietti et al 1994;Kost et al 1999;Li et al 1999; of mutants affecting male progamic phase functions Tang et al 2002), including calcium-mediated signaling remains a challenge because of two major constraints:…”

“…Phenotypic analyses of developing microspores and pollen using DAPI staining were performed as described tions, we developed routine genetic and cytological apin Park et al (1998). In vitro germination assays were perproaches that we have applied here to the analysis of 5 formed using conditions modified from Derksen et al (2002) seth mutations. (Hamamatsu Photonics, Japan).…”