Culture senescence and abscisic acid induce saporin production in cultured roots of Saponaria officinalis

Abstract

The presence and variation of activity of the type 1 ribosome-inactivating protein saporin has been evaluated in cultured roots of the soapwort Saponaria officinalis. Results from western analysis and in vitro protein synthesis inhibition indicate that saporin production is increased in senescing cultures, reaching a maximum value during the late stationary phase. Accordingly, cultures treated with the senescence-related hormone abscisic acid show a significant increase in saporin activity, independently from the culture growth phase. Stress conditions, such as the presence of hydrogen peroxide in the culture medium, had no effect on the modulation of enzymatic activity. The putative regulation of saporin production by abscisic acid and its possible role in accomplishing the ageing programme is discussed.

Differential expression of saporin genes upon wounding, ABA treatment and leaf development

“…4B). These patterns sustain that leaf saporin‐L transcription is developmentally regulated, probably reflecting endogenous leaf physiological changes, such as ageing (Di Cola et al 1999, Stirpe et al 1996). The saporin‐S high steady‐state expression suggests links to constitutive activity of leaves (e.g.…”

“…RIPs have often been reported as proteins induced/ regulated by both wounding and ABA, a hormone involved in abiotic stress signalling (Kawade et al 2008, Song et al 2000, Xu et al 2007). Data on saporin protein regulation on some of these conditions suggested similar responses (Di Cola et al 1999). We have thus decided to verify whether the saporin‐L and ‐ S leaf‐specific gene expression could be correlated with previous data.…”

“…With regard to organ development, most of the studies concerning saporin accumulation have been focussed on seeds and leaves (Ferreras et al 1993). In cultured roots, protein levels were found to increase after ABA treatment (Di Cola et al 1999). Moreover, a dual apoplastic and vacuolar localization has been reported for saporins in seed and leaf (Carzaniga et al 1994).…”

Accumulation of a 31‐kDa glycoprotein in association with the expression of embryogenic potential by spinach callus in culture

“…They are plant enzymes with rRNA N‐glycosidase activity that inhibit protein synthesis by cleaving the N‐glycosidic bond of adenine at a site in 28S rRNA at which elongation factor 2 normally binds (Stirpe and Barbieri 1986). Moreover, these enzymes are induced in response to various types of stress (Reinbothe et al. 1994, Rippmann et al.…”

“…They are plant enzymes with rRNA N-glycosidase activity that inhibit protein synthesis by cleaving the N-glycosidic bond of adenine at a site in 28S rRNA at which elongation factor 2 normally binds (Stirpe and Barbieri 1986). Moreover, these enzymes are induced in response to various types of stress (Reinbothe et al 1994, Rippmann et al 1997, Di Cola et al 1999. It is widely accepted that somatic embryogenesis in plant cells is triggered by various types of stress (Dudits et al, 1995) and therefore RIPs might be involved in a primary reaction that leads to the activation of embryogenic potential.…”