Enhanced Susceptibility of Photosynthesis to Low-Temperature Photoinhibition due to Interruption of Chill-Induced Increase of S-Adenosylmethionine Decarboxylase Activity in Leaves of Spinach (Spinacia oleracea L.)

Abstract

;The possible involvement of polyamines in the chilling tolerance of spinach (Spinacia oleracea L.) was investigated focusing on photosynthesis. During chilling at 8/5°°°°C (day/night) for 6 d, S-adenosylmethionine decarboxylase (SAMDC) activity increased significantly in leaves in parallel with the increase in putrescine and spermidine (Spd) content in leaves and chloroplasts. Treatment of leaves with methylglyoxal-bis(guanylhydrazone) (MGBG), an SAMDC inhibitor, resulted in the deterioration of plant growth and photosynthesis under chilling conditions, which was reversed by the concomitant treatment with Spd through the roots. Plants treated with MGBG showed lower photochemical efficiency of PSII than either the control or plants treated with MGBG plus Spd during chilling and even after transfer to warm conditions, suggesting an increase of photoinhibition due to low Spd in chloroplasts. Indeed, MGBGtreated plants had much lower activities of thylakoid electron transport and enzymes in carbon metabolism as well as higher degrees of lipid peroxidation of thylakoid membranes compared to the control. These results indicate that the enhanced activity of SAMDC with a consequential rise of Spd in chloroplasts is crucial for the cold acclimation of the photosynthetic apparatus in spinach leaves.

Polyamines: potent modulators of plant responses to stress

“…Most widely used inhibitors of various enzymes of PA biosynthesis and catabolism are difluoromethylornithine (DFMO), an irreversible inhibitor of ODC ; difluoromethylarginine (DFMA), an irreversible inhibitor of ADC (Bitonti et al 1987); methylglyoxalbisguanylhydrazine (MGBG), a competitive inhibitor of SAMDC (Williams-Ashman & Schenone 1972); CHA, a competitive inhibitor of SPDS (Hibasami et al 1980); aminoguanidine (AG) for DAO and others. Treatment with biosynthetic inhibitors of PA reduced stress tolerance but this effect is reversed by concomitant application of exogenous PAs (He et al 2002). For instance, DFMA treatment prevented a rise in ADC activity and caused visible injury in barley leaf exposed to ozone relative to the control (Rowland-Bamford et al 1989).…”

Nitric oxide induced by polyamines involves antioxidant systems against chilling stress in tomato (Lycopersicon esculentum Mill.) seedling

“…1a and 1b). To further confirm whether Spd had this effect, we analyzed the levels of NO with MGBG and PTIO pretreatments (Bais and Ravishankar, 2002;He et al, 2002;ArasimowiczJelonek et al, 2009;Gong et al, 2014) before Spd application. Both MGBG and PTIO reduced the NO content induced by Spd under chilling stress (Figs.…”

Improvement of environmental stress tolerance of sweet potato by introduction of genes for spermidine synthase

“…In one experiment, leaf discs were placed in a Petri dish lined with wet filter paper and exposed to 10, 15, 20, and 30°C for 6 hours under a moderate light of 240 mmol m Ϫ2 s Ϫ1 PPFD (chilling treatment). Immediately thereafter, the net photosynthetic rate (O 2 evolution rates in the light) was measured in a Clark-type oxygen electrode (Rank Brothers, Cambridge, UK) at 25°C and a PPFD of 1050 mmol m Ϫ2 s Ϫ1 as described previously (He et al 2002). The net photosynthetic rate of leaf discs that were not subjected to chilling treatment was used as the control.…”

“…A number of physiological studies have indicated important roles of polyamines in plant defense to a wide array of environmental stresses (Bouchereau et al 1999;Shen et al 2000;Bais and Ravishankar 2002;He et al 2002). Now, several gene transfer approaches have shown that the plants overexpressing ADC, ODC or SAMDC transgenes from different sources exhibit enhanced tolerance to salt and drought stresses Wu 2001, 2002;Kumria et al 2002;Mo and Pua 2002;Capell et al 2004).…”