One of the possible mechanisms for the inhibition effect of Tb(III) on peroxidase activity in horseradish (Armoracia rusticana) treated with Tb(III)

Proc. Natl. Acad. Sci. U.S.A.

Zhou

et al. 2014

Self Cite

125

It has long been observed that rare earth elements (REEs) regulate multiple facets of plant growth and development. However, the underlying mechanisms remain largely unclear. Here, using electron microscopic autoradiography, we show the life cycle of a light REE (lanthanum) and a heavy REE (terbium) in horseradish leaf cells. Our data indicate that REEs were first anchored on the plasma membrane in the form of nanoscale particles, and then entered the cells by endocytosis. Consistently, REEs activated endocytosis in plant cells, which may be the cellular basis of REE actions in plants. Moreover, we discovered that a portion of REEs was successively released into the cytoplasm, self-assembled to form nanoscale clusters, and finally deposited in horseradish leaf cells. Taken together, our data reveal the life cycle of REEs and their cellular behaviors in plant cells, which shed light on the cellular mechanisms of REE actions in living organisms.activation | endocytic vesicle S ome trace elements, such as rare earth elements (REEs), have been observed for a long time to be beneficial to plant growth (1, 2). REEs are f-block elements in the periodic table, including 15 lanthanides, plus scandium and yttrium (2). The beneficial effect of REEs on plants was first reported in 1917, when it was found that cerium, an REE, improved physiological activities of water-floss (Spirogyra) (3). Since the 1970s, REEs have been widely used in agriculture as plant growth stimulants (4). Currently, more than 100 of crop species have been applied with REEs, which has increased crop yields by 5-15% (4). In addition, REEs also serve to protect plants against certain plant diseases and some stresses, such as drought, cold, acid rain, or heavy metals (2). The wide use of REEs has caused an overaccumulation of REEs in the ecosystem, including soil (5), atmosphere (6), and water (7). Moreover, it was shown that REEs have dual effects on plant growth: low concentrations of REEs exert positive effects on growth and yield of crops, whereas high concentrations of REEs seem to be harmful for plants, indicating that REEs are not absolutely good for plants (2). Therefore, it is imperative to elucidate how REEs act on plant cells to ensure food safety.Despite of many advances achieved in recent years, the action mechanisms of REEs on plant cells still remain poorly understood (2). Several explanations, which are mainly focused on the physiological roles of REEs in plant cells, have been proposed (2). These mechanisms include the possible changes of photosynthesis, mineral nutrient uptake and metabolism, catalytic activities of some enzymes, hormonal balance, and so forth (2). However, these hypotheses are not connected to any cellular or molecular principles and are therefore far from explaining the action mechanisms of REEs in plants (2,8). In addition, little consensus has yet been reached regarding the life cycle of REEs in plant cells. Some studies report that REEs cannot enter the plant cells but only be localized in apoplast (8-14); other st...

mentioning

confidence: 99%

Rare earth elements activate endocytosis in plant cells

Proc. Natl. Acad. Sci. U.S.A.

Zhou

et al. 2014

Self Cite

125

“…Our previous research has proved that Ca(II) can be substituted by Tb(III), because Tb(III) have been described as Ca(II) analogs and the high charge density of Tb(III) makes them bind more tightly than Ca(II), and about four mole of Tb(III) is bound to one mole of HRP (Guo et al 2008). In this paper, it was found from the results of the MALDI-TOF/MS and ICP-MS that La(III) cannot replace Ca(II), and about one mole of La binds to one mole of HRP.…”

Section: Maldi-tof/ms and Icp-ms Measurementsmentioning

confidence: 99%

“…Our previous study has found that one of the heavy rare earth, terbium, could interact with HRP, leading to the formation of a new terbium-HRP protein. Meanwhile, the formation of the Tb-HRP protein causes the decrease in the activity of HRP (Guo et al 2008). However, the biochemical behavior of light REEs in plant is different from heavy REEs (Ding et al 2006).…”

Section: Introductionmentioning

confidence: 98%

The formation of a new horseradish peroxidase binding rare earth

Jiang

et al. 2009

Environ Chem Lett

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The charge distribution, the isolation, purification, and characterization of horseradish peroxidase (HRP) were investigated. A new HRP protein binding La (La-HRP) was found for the first time in vivo. The molecular weight of the La-HRP protein is about 43,833 Da. The activity index (Rz) of the La-HRP protein (Rz = 2.4) is lower than that of HRP (Rz = 3.1). The La-HRP protein is absorbed in the plasma membrane of the plant and animal, leading to the change in the function of the cell membrane. Therefore, the La-HRP protein is harmful to living organisms.

“…Many toxic mechanisms of REEs on plants have been proposed, including changes in photosynthesis, mineral nutrition, respiration, antioxidant system, and many other processes [1,[19][20][21][22]. In previous studies, we observed that REE ions (III) decreases the activity of peroxidase in horseradish (HRP), one type of antioxidant enzymes, leading to an excessive increase in the free radical content and the subsequent peroxidation of cell membrane lipids in horseradish [23][24][25][26][27][28]. However, peroxidase also plays an important role in the lignification of cell wall [29], indicating that peroxidase is not absolutely good for plants.…”

Section: Introductionmentioning

confidence: 99%

Roles of Horseradish Peroxidase in Response to Terbium Stress

Zhang

Zhou

2014

Biol Trace Elem Res

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The pollution of the environment by rare earth elements (REEs) causes deleterious effects on plants. Peroxidase plays important roles in plant response to various environmental stresses. Here, to further understand the overall roles of peroxidase in response to REE stress, the effects of the REE terbium ion (Tb(3+)) on the peroxidase activity and H2O2 and lignin contents in the leaves and roots of horseradish during different growth stages were simultaneously investigated. The results showed that after 24 and 48 h of Tb(3+) treatment, the peroxidase activity in horseradish leaves decreased, while the H2O2 and lignin contents increased. After a long-term (8 and 16 days) treatment with Tb(3+), these effects were also observed in the roots. The analysis of the changes in peroxidase activity and H2O2 and lignin contents revealed that peroxidase plays important roles in not only reactive oxygen species scavenging but also cell wall lignification in horseradish under Tb(3+) stress. These roles were closely related to the dose of Tb(3+), duration of stress, and growth stages of horseradish.