Rapid accumulation and metabolism of polyphosphoinositol and its possible role in phytoalexin biosynthesis in yeast elicitor-treated Cupressus lusitanica cell cultures

Abstract

Inositol 1,4,5-trisphosphate [Ins(1,4,5)P(3)] rapidly accumulates in elicited Cupressus lusitanica Mill. cultured cells by 4- to 5-fold over the control, and then it is metabolized. Correspondingly, phospholipase C (PLC) activity toward phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P(2)] is stimulated to high levels by the elicitor and then decreases whereas Ins(1,4,5)P(3) phosphatase activity declines at the beginning of elicitation and increases later. These observations indicate that elicitor-induced biosynthesis and dephosphorylation of Ins(1,4,5)P(3) occur simultaneously and that the Ins(1,4,5)P(3) level may be regulated by both PtdIns(4,5)P(2)-PLC and Ins(1,4,5)P(3) phosphatases. Studies on the properties of PLC and Ins(1,4,5)P(3) phosphatases indicate that PLC activity toward PtdIns(4,5)P(2) was optimal at a lower Ca(2+) concentration than activity toward phosphatidylinositol whereas Ins(1,4,5)P(3) phosphatase activity is inhibited by high Ca(2+) concentration. This suggests that Ins(1,4,5)P(3) biosynthesis and degradation may be regulated by free cytosolic Ca(2+). In addition, a relationship between Ins(1,4,5)P(3) signaling and accumulation of a phytoalexin (beta-thujaplicin) is suggested because inhibition or promotion of Ins(1,4,5)P(3) accumulation by neomycin or LiCl affects elicitor-induced production of beta-thujaplicin. Moreover, ruthenium red inhibits elicitor-induced accumulation of beta-thujaplicin while thapsigargin alone induces beta-thujaplicin accumulation. These results suggest that Ca(2+) released from intracellular calcium stores may mediate elicitor-induced accumulation of beta-thujaplicin via an Ins(1,4,5)P(3) signaling pathway, since it is widely accepted that Ins(1,4,5)P(3) can mobilize Ca(2+) from intracellular stores. This work demonstrates an elicitor-triggered Ins(1,4,5)P(3) turnover, defines its enzymatic basis and regulation, and suggests a role for Ins(1,4,5)P(3) in elicitor-induced phytoalexin accumulation via a Ca(2+) signaling pathway.

Contributions of PIP2-specific-phospholipase C and free salicylic acid to heat acclimation-induced thermotolerance in pea leaves

“…The properties of PLC toward PIP 2 from pea leaves examined in this study (Fig. 1) are consistent with these previous reports (Arz and Grambow, 1994;Zhao et al, 2004). Deoxycholate, an ionic detergent, reduced the Ca 2+ requirement 10-fold for PIP 2 -PLC ( Fig.…”

“…These two second messengers play key roles in amplifying extracellular signals and regulating various intracellular processes triggered by abiotic and biotic stimuli (Cho et al, 1995;Dewald et al, 2001;Pical et al, 1999;Reggiani and Laoreti, 2000;Ruelland et al, 2002;Takahashi et al, 2001;Zhao et al, 2004). As such, the activation of PLC was usually regarded as an early signal event in response to external stresses.…”

Different responses of shoot and root cultures of Glehnia littoralis to yeast extract

“…1, YE affected root growth positively but leaf growth negatively. Historically, YE has been used as a nutrient [17,18], but, more recently, it has often been employed as an elicitor [19][20][21]. Yeast extract seems to act bifunctionally on the root but only as an elicitor in the leaf of G. littoralis.…”

Phospholipidic signaling and vanillin production in response to salicylic acid and methyl jasmonate in Capsicum chinense J. cells

“…They are present in almost all plant tissues, but levels of these phytoregulators increase in response to stressful conditions [14,15]. Since secondary metabolite accumulation is a common response to stress and both SA and MJ mediate cell response to stress, these compounds have been used as elicitors to increase secondary metabolite production in suspension cell cultures of different species, including Capsicum [16,17]. Capsaicinoids, the secondary metabolites responsible for the pungency of chili peppers, occur only in the Capsicum genus [18].…”