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Translocation of phospholipase A2α to apoplasts is modulated by developmental stages and bacterial infection in Arabidopsis.

Jung J, Kumar K, Lee HY, Park YI, Cho HT, Ryu SB - Front Plant Sci (2012)

Bottom Line: The present study shows that PLA(2)α possesses unique characteristics in terms of spatiotemporal subcellular localization, as compared with the other paralogs that remain in the ER and/or Golgi apparatus during secretory processes.When Pseudomonas syringae pv.~tomato DC3000 carrying the avirulent factor avrRpm1 infects the apoplasts of host plants, PLA(2)α rapidly translocates to the apoplasts where bacteria attempt to become established.It would be interesting to investigate if PLA(2)α functions in plant defense responses at apoplasts where secreted PLA(2)α confronts with invading pathogens.

View Article: PubMed Central - PubMed

Affiliation: Environmental Biotechnology Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, Korea.

ABSTRACT
Phospholipase A(2) (PLA(2)) hydrolyzes phospholipids at the sn-2 position to yield lysophospholipids and free fatty acids. Of the four paralogs expressed in Arabidopsis, the cellular functions of PLA(2)α in planta are poorly understood. The present study shows that PLA(2)α possesses unique characteristics in terms of spatiotemporal subcellular localization, as compared with the other paralogs that remain in the ER and/or Golgi apparatus during secretory processes. Only PLA(2)α is secreted out to extracellular spaces, and its secretion to apoplasts is modulated according to the developmental stages of plant tissues. Observation of PLA(2)α-RFP transgenic plants suggests that PLA(2)α localizes mostly at the Golgi bodies in actively growing leaf tissues, but is gradually translocated to apoplasts as the leaves become mature. When Pseudomonas syringae pv.~tomato DC3000 carrying the avirulent factor avrRpm1 infects the apoplasts of host plants, PLA(2)α rapidly translocates to the apoplasts where bacteria attempt to become established. PLA(2)α promoter::GUS assays show that PLA(2)α gene expression is controlled in a developmental stage- and tissue-specific manner. It would be interesting to investigate if PLA(2)α functions in plant defense responses at apoplasts where secreted PLA(2)α confronts with invading pathogens.

No MeSH data available.


Subcellular localization of PLA2α at different leaf ages in PLA2α-RFP transgenic Arabidopsis plants.(A,B) Epidermal cells in pre-mature leaf tissues (A) and mature leaf tissues (B) from Pro35SPLA2α-RFP transgenic Arabidopsis plants (4-week-old) were viewed using confocal microscopy. (C) Mature leaf tissues were incubated in 1 N KNO3 to induce plasmolysis before being viewed with confocal microscopy. The slightly decreased clarity of images in (C) appears to result from the diffusion of PLA2α-RFP into the expanded apoplasts due to plasmolysis. White arrows in (C) indicate the plasmolyzed plasma membrane, whereas black arrows indicate extracellular spaces. Fluorescent (top), bright field (middle), and merged images (bottom) are presented. Bars = 20 μm.
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Figure 2: Subcellular localization of PLA2α at different leaf ages in PLA2α-RFP transgenic Arabidopsis plants.(A,B) Epidermal cells in pre-mature leaf tissues (A) and mature leaf tissues (B) from Pro35SPLA2α-RFP transgenic Arabidopsis plants (4-week-old) were viewed using confocal microscopy. (C) Mature leaf tissues were incubated in 1 N KNO3 to induce plasmolysis before being viewed with confocal microscopy. The slightly decreased clarity of images in (C) appears to result from the diffusion of PLA2α-RFP into the expanded apoplasts due to plasmolysis. White arrows in (C) indicate the plasmolyzed plasma membrane, whereas black arrows indicate extracellular spaces. Fluorescent (top), bright field (middle), and merged images (bottom) are presented. Bars = 20 μm.

Mentions: Lee et al. (2010) reported that fluorescence signals for PLA2α-fusion proteins were observed at the Golgi apparatus of root hair cells. However, Froidure et al. (2010) showed time-dependent localization of PLA2α using a transient expression system incorporating N. tabacum. The YFP reporter fused with PLA2α was detected in cytoplasmic vesicles around the nucleus 36 h after agroinfiltration to tobacco leaves, and was detected at the extracellular spaces outside the cells at a later time point (48 h after agroinfiltration). To resolve these inconsistencies, we investigated in more detail the subcellular localization of PLA2α by analyzing the fluorescence of fusion proteins in transgenic plants carrying Pro35S::PLA2α-RFP. The leaves of 4-week-old PLA2α-RFP transgenic seedlings were viewed using a laser scanning confocal microscope. The results showed that the subcellular localization of PLA2α was dependent on the developmental stages of leaf tissue. PLA2α-RFP fusion proteins were present primarily at the Golgi apparatus in pre-mature young leaves (Figure 2A), whereas in mature leaves, they were detected primarily in the apoplasts (Figure 2B). Even after cell plasmolysis was induced by treatment with 1 N KNO3 for 5 min, the PLA2α-RFP signal remained in the extracellular spaces or diffused into the gap between the cell wall and the plasma membrane that is induced by plasmolysis (Figure 2C). These results indicate that PLA2α is indeed localized in the apoplasts of mature leaves.


Translocation of phospholipase A2α to apoplasts is modulated by developmental stages and bacterial infection in Arabidopsis.

Jung J, Kumar K, Lee HY, Park YI, Cho HT, Ryu SB - Front Plant Sci (2012)

Subcellular localization of PLA2α at different leaf ages in PLA2α-RFP transgenic Arabidopsis plants.(A,B) Epidermal cells in pre-mature leaf tissues (A) and mature leaf tissues (B) from Pro35SPLA2α-RFP transgenic Arabidopsis plants (4-week-old) were viewed using confocal microscopy. (C) Mature leaf tissues were incubated in 1 N KNO3 to induce plasmolysis before being viewed with confocal microscopy. The slightly decreased clarity of images in (C) appears to result from the diffusion of PLA2α-RFP into the expanded apoplasts due to plasmolysis. White arrows in (C) indicate the plasmolyzed plasma membrane, whereas black arrows indicate extracellular spaces. Fluorescent (top), bright field (middle), and merged images (bottom) are presented. Bars = 20 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3376726&req=5

Figure 2: Subcellular localization of PLA2α at different leaf ages in PLA2α-RFP transgenic Arabidopsis plants.(A,B) Epidermal cells in pre-mature leaf tissues (A) and mature leaf tissues (B) from Pro35SPLA2α-RFP transgenic Arabidopsis plants (4-week-old) were viewed using confocal microscopy. (C) Mature leaf tissues were incubated in 1 N KNO3 to induce plasmolysis before being viewed with confocal microscopy. The slightly decreased clarity of images in (C) appears to result from the diffusion of PLA2α-RFP into the expanded apoplasts due to plasmolysis. White arrows in (C) indicate the plasmolyzed plasma membrane, whereas black arrows indicate extracellular spaces. Fluorescent (top), bright field (middle), and merged images (bottom) are presented. Bars = 20 μm.
Mentions: Lee et al. (2010) reported that fluorescence signals for PLA2α-fusion proteins were observed at the Golgi apparatus of root hair cells. However, Froidure et al. (2010) showed time-dependent localization of PLA2α using a transient expression system incorporating N. tabacum. The YFP reporter fused with PLA2α was detected in cytoplasmic vesicles around the nucleus 36 h after agroinfiltration to tobacco leaves, and was detected at the extracellular spaces outside the cells at a later time point (48 h after agroinfiltration). To resolve these inconsistencies, we investigated in more detail the subcellular localization of PLA2α by analyzing the fluorescence of fusion proteins in transgenic plants carrying Pro35S::PLA2α-RFP. The leaves of 4-week-old PLA2α-RFP transgenic seedlings were viewed using a laser scanning confocal microscope. The results showed that the subcellular localization of PLA2α was dependent on the developmental stages of leaf tissue. PLA2α-RFP fusion proteins were present primarily at the Golgi apparatus in pre-mature young leaves (Figure 2A), whereas in mature leaves, they were detected primarily in the apoplasts (Figure 2B). Even after cell plasmolysis was induced by treatment with 1 N KNO3 for 5 min, the PLA2α-RFP signal remained in the extracellular spaces or diffused into the gap between the cell wall and the plasma membrane that is induced by plasmolysis (Figure 2C). These results indicate that PLA2α is indeed localized in the apoplasts of mature leaves.

Bottom Line: The present study shows that PLA(2)α possesses unique characteristics in terms of spatiotemporal subcellular localization, as compared with the other paralogs that remain in the ER and/or Golgi apparatus during secretory processes.When Pseudomonas syringae pv.~tomato DC3000 carrying the avirulent factor avrRpm1 infects the apoplasts of host plants, PLA(2)α rapidly translocates to the apoplasts where bacteria attempt to become established.It would be interesting to investigate if PLA(2)α functions in plant defense responses at apoplasts where secreted PLA(2)α confronts with invading pathogens.

View Article: PubMed Central - PubMed

Affiliation: Environmental Biotechnology Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, Korea.

ABSTRACT
Phospholipase A(2) (PLA(2)) hydrolyzes phospholipids at the sn-2 position to yield lysophospholipids and free fatty acids. Of the four paralogs expressed in Arabidopsis, the cellular functions of PLA(2)α in planta are poorly understood. The present study shows that PLA(2)α possesses unique characteristics in terms of spatiotemporal subcellular localization, as compared with the other paralogs that remain in the ER and/or Golgi apparatus during secretory processes. Only PLA(2)α is secreted out to extracellular spaces, and its secretion to apoplasts is modulated according to the developmental stages of plant tissues. Observation of PLA(2)α-RFP transgenic plants suggests that PLA(2)α localizes mostly at the Golgi bodies in actively growing leaf tissues, but is gradually translocated to apoplasts as the leaves become mature. When Pseudomonas syringae pv.~tomato DC3000 carrying the avirulent factor avrRpm1 infects the apoplasts of host plants, PLA(2)α rapidly translocates to the apoplasts where bacteria attempt to become established. PLA(2)α promoter::GUS assays show that PLA(2)α gene expression is controlled in a developmental stage- and tissue-specific manner. It would be interesting to investigate if PLA(2)α functions in plant defense responses at apoplasts where secreted PLA(2)α confronts with invading pathogens.

No MeSH data available.