Programmed cell death during androgenesis in Hordeum vulgare L.

Abstract

For the production of (doubled) haploid plants from microspores, via gametophytic embryogenesis, a specific developmental stage (at the verge of mitosis) in combination with stressful pretreatment (starvation in combination with salt and osmotic stresses) of anthers and microspores generally is essential (Heberle-Bors 1989; Hoekstra et al. 1992; 1997). During this pretreatment, microspores change into cells that are called embryogenic microspores (Hoekstra et al. 1993). Little is known about the biological processes occurring during pretreatment, however, understanding these processes is not only of importance for breeding programs in agriculture but also of fundamental interest for the study of developmental switches. In barley, a few studies have been performed to investigate the effects of anther pretreatment on gametophytic embryogenesis. It was found that pretreatment with a salt solution containing mannitol is the best condition for plant production (Hoekstra et al. 1996). Davies and Jones (1991) suggest that, in response to certain stress treatments like osmotic pressure and cold, ABA is produced. Pretreatment of tobacco anthers by mannitol caused an increase in endogenous ABA level (Imamura and Harada 1980). Furthermore, relatively high endogenous ABA levels are correlated with high embryogenic potential of Pennisetum and carrot cells (Rajasekaran et al. 1987a; Rajasekaran et al. 1987b; Kiyosue et al. 1992; Reynolds and Crawford 1996). These observations suggest a possible role for ABA in androgenesis.