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Burst of reactive oxygen species in pedicel-mediated fruit abscission after carbohydrate supply was cut off in longan (Dimocarpus longan).

Yang Z, Zhong X, Fan Y, Wang H, Li J, Huang X - Front Plant Sci (2015)

Bottom Line: H2O2 was found exclusively in the cell walls 2 DAT, almost disappeared 3 DAT, and reappeared in the mitochondria and cell walls 4 DAT.The burst of ROS coincided with a sharp increase in the activity of PM-bound NADPH oxidase in the pedicel.Accompanying the reduction in H2O2 abundance, there was a sharp decrease in PM-bound NADPH oxidase activity after 1 DAT in the treated fruit.

View Article: PubMed Central - PubMed

Affiliation: Physiological Laboratory for South China Fruits, College of Horticulture, South China Agricultural University , Guangzhou, China ; Tropical Crops Genetic Resources Institute, Chinese Academy of Tropical Agricultural Sciences , Danzhou, China.

ABSTRACT
Cutting off carbohydrate supply to longan (Dimocarpus longan Lour.) fruit by girdling and defoliation or by detachment induced 100% abscission within a few days. We used these treatments to study the involvement of reactive oxygen species (ROS) in fruit abscission. Girdling plus defoliation decreased sugar concentrations in the fruit and pedicel and depleted starch grains in the chloroplasts in the cells of abscission zone. Prior to the occurrence of intensive fruit abscission, there was a burst in ROS in the pedicel, which peaked at 1 day after treatment (DAT), when H2O2 in the abscission zone was found to be chiefly located along the plasma membrane (PM). H2O2 was found exclusively in the cell walls 2 DAT, almost disappeared 3 DAT, and reappeared in the mitochondria and cell walls 4 DAT. Signs of cell death such as cytoplasm breakdown were apparent from 3 DAT. The burst of ROS coincided with a sharp increase in the activity of PM-bound NADPH oxidase in the pedicel. At the same time, activities of antioxidant enzymes including superoxide dismutase (SOD), catalase, and peroxidase (POD) were all increased by the treatment and maintained higher than those in the control. Accompanying the reduction in H2O2 abundance, there was a sharp decrease in PM-bound NADPH oxidase activity after 1 DAT in the treated fruit. H2O2 scavenger dimethylthiourea (DMTU, 1 g L(-1)) significantly inhibited fruit abscission in detached fruit clusters and suppressed the increase in cellulase activity in the abscission zone. These results suggest that fruit abscission induced by carbohydrate stress is mediated by ROS. Roles of ROS in regulating fruit abscission were discussed in relation to its subcellular distribution.

No MeSH data available.


Related in: MedlinePlus

Effect of girdling plus defoliation on the activities of PM-bound NADPH oxidase (A), superoxide dismutase (SOD) (B), catalase (CAT) (C), and peroxidase (POD) (D) in the pedicel of longan. Vertical bars indicate standard errors. Asterisks indicate that the paired means were significantly different at P = 0.05, t-test (n = 5).
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Figure 5: Effect of girdling plus defoliation on the activities of PM-bound NADPH oxidase (A), superoxide dismutase (SOD) (B), catalase (CAT) (C), and peroxidase (POD) (D) in the pedicel of longan. Vertical bars indicate standard errors. Asterisks indicate that the paired means were significantly different at P = 0.05, t-test (n = 5).

Mentions: Coinciding with the changes in the abundance of ROS, the activity of PM-bound NADPH oxidase in the pedicel increased drastically within 12 h after girdling plus defoliation, peaked around 24 h after the treatment, and then decreased sharply although remained higher than the control (Figure 5A). The treatment also induced significant increase in SOD activity (Figure 5B), which converts superoxide anion radical generated by PM-bound NADPH oxidase into H2O2. From 24 to 72 h after the girdling plus defoliation, the activities of H2O2-scavenging enzymes, i.e., CAT (Figure 5C) and POD (Figure 5D) were significantly higher in the treated pedicel than in the control. The two enzymes displayed opposite trends, CAT decreasing while POD increasing during fruit development.


Burst of reactive oxygen species in pedicel-mediated fruit abscission after carbohydrate supply was cut off in longan (Dimocarpus longan).

Yang Z, Zhong X, Fan Y, Wang H, Li J, Huang X - Front Plant Sci (2015)

Effect of girdling plus defoliation on the activities of PM-bound NADPH oxidase (A), superoxide dismutase (SOD) (B), catalase (CAT) (C), and peroxidase (POD) (D) in the pedicel of longan. Vertical bars indicate standard errors. Asterisks indicate that the paired means were significantly different at P = 0.05, t-test (n = 5).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4443251&req=5

Figure 5: Effect of girdling plus defoliation on the activities of PM-bound NADPH oxidase (A), superoxide dismutase (SOD) (B), catalase (CAT) (C), and peroxidase (POD) (D) in the pedicel of longan. Vertical bars indicate standard errors. Asterisks indicate that the paired means were significantly different at P = 0.05, t-test (n = 5).
Mentions: Coinciding with the changes in the abundance of ROS, the activity of PM-bound NADPH oxidase in the pedicel increased drastically within 12 h after girdling plus defoliation, peaked around 24 h after the treatment, and then decreased sharply although remained higher than the control (Figure 5A). The treatment also induced significant increase in SOD activity (Figure 5B), which converts superoxide anion radical generated by PM-bound NADPH oxidase into H2O2. From 24 to 72 h after the girdling plus defoliation, the activities of H2O2-scavenging enzymes, i.e., CAT (Figure 5C) and POD (Figure 5D) were significantly higher in the treated pedicel than in the control. The two enzymes displayed opposite trends, CAT decreasing while POD increasing during fruit development.

Bottom Line: H2O2 was found exclusively in the cell walls 2 DAT, almost disappeared 3 DAT, and reappeared in the mitochondria and cell walls 4 DAT.The burst of ROS coincided with a sharp increase in the activity of PM-bound NADPH oxidase in the pedicel.Accompanying the reduction in H2O2 abundance, there was a sharp decrease in PM-bound NADPH oxidase activity after 1 DAT in the treated fruit.

View Article: PubMed Central - PubMed

Affiliation: Physiological Laboratory for South China Fruits, College of Horticulture, South China Agricultural University , Guangzhou, China ; Tropical Crops Genetic Resources Institute, Chinese Academy of Tropical Agricultural Sciences , Danzhou, China.

ABSTRACT
Cutting off carbohydrate supply to longan (Dimocarpus longan Lour.) fruit by girdling and defoliation or by detachment induced 100% abscission within a few days. We used these treatments to study the involvement of reactive oxygen species (ROS) in fruit abscission. Girdling plus defoliation decreased sugar concentrations in the fruit and pedicel and depleted starch grains in the chloroplasts in the cells of abscission zone. Prior to the occurrence of intensive fruit abscission, there was a burst in ROS in the pedicel, which peaked at 1 day after treatment (DAT), when H2O2 in the abscission zone was found to be chiefly located along the plasma membrane (PM). H2O2 was found exclusively in the cell walls 2 DAT, almost disappeared 3 DAT, and reappeared in the mitochondria and cell walls 4 DAT. Signs of cell death such as cytoplasm breakdown were apparent from 3 DAT. The burst of ROS coincided with a sharp increase in the activity of PM-bound NADPH oxidase in the pedicel. At the same time, activities of antioxidant enzymes including superoxide dismutase (SOD), catalase, and peroxidase (POD) were all increased by the treatment and maintained higher than those in the control. Accompanying the reduction in H2O2 abundance, there was a sharp decrease in PM-bound NADPH oxidase activity after 1 DAT in the treated fruit. H2O2 scavenger dimethylthiourea (DMTU, 1 g L(-1)) significantly inhibited fruit abscission in detached fruit clusters and suppressed the increase in cellulase activity in the abscission zone. These results suggest that fruit abscission induced by carbohydrate stress is mediated by ROS. Roles of ROS in regulating fruit abscission were discussed in relation to its subcellular distribution.

No MeSH data available.


Related in: MedlinePlus