Naslov
Ammonium-related metabolic changes affect somatic embryogenesis in pumpkin (Cucurbita pepo L.)

Autori
Mihaljević, Snježana ; Radić, Sandra ; Bauer, Nataša ; Garić, Rade ; Mihaljević, Branka ; Horvat, Gordana ; Leljak-Levanić, Dunja ; Jelaska, Sibila

Izvornik
Journal of plant physiology (0176-1617) 168 (2011), 16; 1943-1951

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
antioxidative enzymes ; Cucurbita pepo ; glutamine synthetase ; nitrogen supply ; phenylalanine ammonia-lyase

Sažetak
Somatic embryogenesis in pumpkin can be induced on auxin-containing medium but also on hormone-free medium containing 1 mM ammonium (NH4+) as the sole source of nitrogen. Growth of NH4+-induced embryogenic tissue was slow and caused considerable acidification of the culture medium. Small spherical cells with dense cytoplasma formed proembryogenic cell clusters that could not develop into late stage embryos. Buffering of NH4+medium with 25 mM 2-(N-morpholino)-ethane-sulfonic acid enhanced tissue proliferation, but no further differentiation was observed. Later stage embryos developed only after re-supply of nitrogen in form of nitrate or L-glutamine. Effects of nitrogen status and pH of culture media on ammonium assimilation were analyzined by following the activity of glutamine synthetase (GS) in relation to phenylalanine ammonia-lyase (PAL). Increased activity of GS and PAL in NH4-induced tissue coincided with significantly higher activity of stress-related enzymes superoxide dismutase (SOD) and soluble peroxidase (POD) what indicated oxidative stress response of embryogenic tissue to NH4+as the sole source of nitrogen. In addition, considerable increase was observed in callose accumulation and esterase activity, the early markers of somatic emrbyogenesis. Activity of stress-related enzymes decreased after the re-supply of nitrate (20 mM) or Gln (10 mM) in combination with NH4+ (1 mM) that subsequently triggered globular embryo development. Together, results suggest that stress responses, as affected by nitrogen supply, contribute to the regulation of embryogenic competence in pumpkin.

Izvorni jezik
Engleski

Znanstvena područja
Biologija

POVEZANOST RADA