Cellular approach to the study of androgenesis in maize anthers: Immunocytochemical evidence of the involvement of the ubiquitin degradative pathway in androgenesis induction
Jd. Alche et al., Cellular approach to the study of androgenesis in maize anthers: Immunocytochemical evidence of the involvement of the ubiquitin degradative pathway in androgenesis induction, J PLANT PHY, 156(2), 2000, pp. 146-155
Maize anthers in the late-uninucleate stage, corresponding to a DH 109 x ZK
191/a F1 hybrid line, were induced to produce embryoids by cold pre-treatm
ent and incubation onto a modified YP medium. LM observation of sections of
the anthers showed the existence of bicellular microspores two days after
starting the culture. Several types of multicellular microspores (MCM) and
multinucleate microspores (MNM) appeared from the fifth day after culture o
nwards, together with many degenerated, non-induced microspores. This abund
ance of forms reveals the presence of different patterns of division and de
velopment. Ultrastructural observation of these cellular forms showed parti
cular features, such as the presence of numerous nuclear pores in early sta
ges of induction and the formation of a thick independent cell wall underne
ath the microspore intine. A certain degree of polarity in these structures
was also frequently observed. Proembryoids appeared after 10-13 days of cu
lture, whereas embryo-like structures were observed several days later (16
days of culture).
Immunocytochemical studies were carried out on semithin sections of the ant
hers using a commercially available polyclonal antibody to ubiquitin. Sligh
t labeling nas consistently found in most cell types, excluding degenerated
and non-induced microspores. The intensity of the labeling was found to be
substantially greater in putative androgenic MCM. A model for the involvem
ent: of the ubiquitin-mediated degradation pathway in pollen cell cycle con
trol and androgenesis induction is proposed.