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Polyphenol oxidase affects normal nodule development in red clover (Trifolium pratense L.).

Webb KJ, Cookson A, Allison G, Sullivan ML, Winters AL - Front Plant Sci (2014)

Bottom Line: However, absence of PPO resulted in a more reduced environment in all tissues, as measured by redox potential, and caused subtle developmental changes in nodules.Developing nodules lacking PPO were longer, and there were more cell layers within the squashed cell layer (SCL), but the walls of these cells were less thickened and the cells were less squashed.Within the N2-fixing zone, bacteroids appeared more granular and were less tightly packed together, and were similar to developmentally compromised bacteroids elicited by catalase mutant rhizobia reported elsewhere.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biological, Environmental and Rural Sciences, Aberystwyth University Aberystwyth, UK.

ABSTRACT
Polyphenol oxidase (PPO) may have multiple functions in tissues depending on its cellular or tissue localization. Here we use PPO RNAi transformants of red clover (Trifolium pratense) to determine the role PPO plays in normal development of plants, and especially in N2-fixing nodules. In red clover, PPO was not essential for either growth or nodule production, or for nodule function in plants grown under optimal, N-free conditions. However, absence of PPO resulted in a more reduced environment in all tissues, as measured by redox potential, and caused subtle developmental changes in nodules. Leaves and, to a lesser extent nodules, lacking PPO tended to accumulate phenolic compounds. A comparison of nodules of two representative contrasting clones by microscopy revealed that nodules lacking PPO were morphologically and anatomically subtly altered, and that phenolics accumulated in different cells and tissues. Developing nodules lacking PPO were longer, and there were more cell layers within the squashed cell layer (SCL), but the walls of these cells were less thickened and the cells were less squashed. Within the N2-fixing zone, bacteroids appeared more granular and were less tightly packed together, and were similar to developmentally compromised bacteroids elicited by catalase mutant rhizobia reported elsewhere.

No MeSH data available.


Related in: MedlinePlus

Light and TEM micrographs of nodules of sections of two contrasting PPO phenotypes, WT RC11 and RNAi RC4 plants. (A) and (B), Light micrographs showing nodule cortex (nc), nodule parenchyma (np), SCL and bacteroids (b). (A) WT RC11 nodules had 3–4 celled SCL and rounded bacteroids. Average width cells of SCL = 37.53 ± 0.860 μm, average area cells nc = 493.7 ± 25.62 μm2. B, RNAi RC4 nodules showing wider 5–6 celled SCL, which are less squashed and, more granular bacteroids (b). Average width cells of SCL = 60.05 ± 1.079 μm, average area cells nc = 1164.8 ± 117.32 μm2. (C,D) TEM micrographs showing bacteroids within nodules (b). (C) WT RC11 rounded tightly packed bacteroids. (D) RNAi RC4 elongated granular bacteroids (b). Bars (A,B) = 25 μm, (C,D) = 500 nm.
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Figure 2: Light and TEM micrographs of nodules of sections of two contrasting PPO phenotypes, WT RC11 and RNAi RC4 plants. (A) and (B), Light micrographs showing nodule cortex (nc), nodule parenchyma (np), SCL and bacteroids (b). (A) WT RC11 nodules had 3–4 celled SCL and rounded bacteroids. Average width cells of SCL = 37.53 ± 0.860 μm, average area cells nc = 493.7 ± 25.62 μm2. B, RNAi RC4 nodules showing wider 5–6 celled SCL, which are less squashed and, more granular bacteroids (b). Average width cells of SCL = 60.05 ± 1.079 μm, average area cells nc = 1164.8 ± 117.32 μm2. (C,D) TEM micrographs showing bacteroids within nodules (b). (C) WT RC11 rounded tightly packed bacteroids. (D) RNAi RC4 elongated granular bacteroids (b). Bars (A,B) = 25 μm, (C,D) = 500 nm.

Mentions: Distribution of phenolics in nodule sections of two contrasting polyphenol oxidase (PPO) phenotypes, wild-type (WT) RC11 and RNAi RC4 plants as visualized by Raman microspectrometry overlaying an image generated by white reflected light. Raman images were collected using a 514 nm laser from 1400 to 1800 cm-1 and over-laid the same image collected by reflected white light in unstained ultrathin sections of two nodules in longitudinal section (A) WT RC11 and (B) RNAi RC4. The nodule meristem (m), epidermis (e), nodule cortex (nc), nodule parenchyma (np) and N2-fixing bacteroids (b) are clearly visible, along with the fully developed squashed cell layer (SCL). The white, dashed rectangles indicate the regions either side of the meristem where the SCL begins to differentiate; this region in another nodule is analyzed further by transmission electron microscopy (TEM) in Figure 2. The colors represent concentration of phenolics (as visualized by Raman emission at 1601 cm-1), from transparent equating with low levels of phenolics through black – purple – blue – white – green – yellow – orange – to red equating with high levels of phenolics. Bars = 200 μm.


Polyphenol oxidase affects normal nodule development in red clover (Trifolium pratense L.).

Webb KJ, Cookson A, Allison G, Sullivan ML, Winters AL - Front Plant Sci (2014)

Light and TEM micrographs of nodules of sections of two contrasting PPO phenotypes, WT RC11 and RNAi RC4 plants. (A) and (B), Light micrographs showing nodule cortex (nc), nodule parenchyma (np), SCL and bacteroids (b). (A) WT RC11 nodules had 3–4 celled SCL and rounded bacteroids. Average width cells of SCL = 37.53 ± 0.860 μm, average area cells nc = 493.7 ± 25.62 μm2. B, RNAi RC4 nodules showing wider 5–6 celled SCL, which are less squashed and, more granular bacteroids (b). Average width cells of SCL = 60.05 ± 1.079 μm, average area cells nc = 1164.8 ± 117.32 μm2. (C,D) TEM micrographs showing bacteroids within nodules (b). (C) WT RC11 rounded tightly packed bacteroids. (D) RNAi RC4 elongated granular bacteroids (b). Bars (A,B) = 25 μm, (C,D) = 500 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4269121&req=5

Figure 2: Light and TEM micrographs of nodules of sections of two contrasting PPO phenotypes, WT RC11 and RNAi RC4 plants. (A) and (B), Light micrographs showing nodule cortex (nc), nodule parenchyma (np), SCL and bacteroids (b). (A) WT RC11 nodules had 3–4 celled SCL and rounded bacteroids. Average width cells of SCL = 37.53 ± 0.860 μm, average area cells nc = 493.7 ± 25.62 μm2. B, RNAi RC4 nodules showing wider 5–6 celled SCL, which are less squashed and, more granular bacteroids (b). Average width cells of SCL = 60.05 ± 1.079 μm, average area cells nc = 1164.8 ± 117.32 μm2. (C,D) TEM micrographs showing bacteroids within nodules (b). (C) WT RC11 rounded tightly packed bacteroids. (D) RNAi RC4 elongated granular bacteroids (b). Bars (A,B) = 25 μm, (C,D) = 500 nm.
Mentions: Distribution of phenolics in nodule sections of two contrasting polyphenol oxidase (PPO) phenotypes, wild-type (WT) RC11 and RNAi RC4 plants as visualized by Raman microspectrometry overlaying an image generated by white reflected light. Raman images were collected using a 514 nm laser from 1400 to 1800 cm-1 and over-laid the same image collected by reflected white light in unstained ultrathin sections of two nodules in longitudinal section (A) WT RC11 and (B) RNAi RC4. The nodule meristem (m), epidermis (e), nodule cortex (nc), nodule parenchyma (np) and N2-fixing bacteroids (b) are clearly visible, along with the fully developed squashed cell layer (SCL). The white, dashed rectangles indicate the regions either side of the meristem where the SCL begins to differentiate; this region in another nodule is analyzed further by transmission electron microscopy (TEM) in Figure 2. The colors represent concentration of phenolics (as visualized by Raman emission at 1601 cm-1), from transparent equating with low levels of phenolics through black – purple – blue – white – green – yellow – orange – to red equating with high levels of phenolics. Bars = 200 μm.

Bottom Line: However, absence of PPO resulted in a more reduced environment in all tissues, as measured by redox potential, and caused subtle developmental changes in nodules.Developing nodules lacking PPO were longer, and there were more cell layers within the squashed cell layer (SCL), but the walls of these cells were less thickened and the cells were less squashed.Within the N2-fixing zone, bacteroids appeared more granular and were less tightly packed together, and were similar to developmentally compromised bacteroids elicited by catalase mutant rhizobia reported elsewhere.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biological, Environmental and Rural Sciences, Aberystwyth University Aberystwyth, UK.

ABSTRACT
Polyphenol oxidase (PPO) may have multiple functions in tissues depending on its cellular or tissue localization. Here we use PPO RNAi transformants of red clover (Trifolium pratense) to determine the role PPO plays in normal development of plants, and especially in N2-fixing nodules. In red clover, PPO was not essential for either growth or nodule production, or for nodule function in plants grown under optimal, N-free conditions. However, absence of PPO resulted in a more reduced environment in all tissues, as measured by redox potential, and caused subtle developmental changes in nodules. Leaves and, to a lesser extent nodules, lacking PPO tended to accumulate phenolic compounds. A comparison of nodules of two representative contrasting clones by microscopy revealed that nodules lacking PPO were morphologically and anatomically subtly altered, and that phenolics accumulated in different cells and tissues. Developing nodules lacking PPO were longer, and there were more cell layers within the squashed cell layer (SCL), but the walls of these cells were less thickened and the cells were less squashed. Within the N2-fixing zone, bacteroids appeared more granular and were less tightly packed together, and were similar to developmentally compromised bacteroids elicited by catalase mutant rhizobia reported elsewhere.

No MeSH data available.


Related in: MedlinePlus