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Quantitative analysis of organelle distribution and dynamics in Physcomitrella patens protonemal cells - PubMed

  • ️Sun Jan 01 2012

Quantitative analysis of organelle distribution and dynamics in Physcomitrella patens protonemal cells

Fabienne Furt et al. BMC Plant Biol. 2012.

Abstract

Background: In the last decade, the moss Physcomitrella patens has emerged as a powerful plant model system, amenable for genetic manipulations not possible in any other plant. This moss is particularly well suited for plant polarized cell growth studies, as in its protonemal phase, expansion is restricted to the tip of its cells. Based on pollen tube and root hair studies, it is well known that tip growth requires active secretion and high polarization of the cellular components. However, such information is still missing in Physcomitrella patens. To gain insight into the mechanisms underlying the participation of organelle organization in tip growth, it is essential to determine the distribution and the dynamics of the organelles in moss cells.

Results: We used fluorescent protein fusions to visualize and track Golgi dictyosomes, mitochondria, and peroxisomes in live protonemal cells. We also visualized and tracked chloroplasts based on chlorophyll auto-fluorescence. We showed that in protonemata all four organelles are distributed in a gradient from the tip of the apical cell to the base of the sub-apical cell. For example, the density of Golgi dictyosomes is 4.7 and 3.4 times higher at the tip than at the base in caulonemata and chloronemata respectively. While Golgi stacks are concentrated at the extreme tip of the caulonemata, chloroplasts and peroxisomes are totally excluded. Interestingly, caulonemata, which grow faster than chloronemata, also contain significantly more Golgi dictyosomes and fewer chloroplasts than chloronemata. Moreover, the motility analysis revealed that organelles in protonemata move with low persistency and average instantaneous speeds ranging from 29 to 75 nm/s, which are at least three orders of magnitude slower than those of pollen tube or root hair organelles.

Conclusions: To our knowledge, this study reports the first quantitative analysis of organelles in Physcomitrella patens and will make possible comparisons of the distribution and dynamics of organelles from different tip growing plant cells, thus enhancing our understanding of the mechanisms of plant polarized cell growth.

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Figures

Figure 1
Figure 1

Experimental design of organelle imaging inPhyscomitrella patensprotonemata. (A) Five zones have been imaged along caulonemata and chloronemata and six areas have been defined for the quantitative analysis with B: Base; N: Nuclear area; To: Tip-oriented area; T: Tip. (B) Representative morphologies of chloroplasts, mitochondria (Mito), Golgi dictyosomes (Golgi) and peroxisomes (Perox) detected in moss protonemal cells. Scale bars 2 μm.

Figure 2
Figure 2

Peroxisomes and chloroplasts distribution inPhyscomitrella patensprotonemata. Bright field and confocal images of 5 distinct zones in caulonemata (A) and chloronemata (B) expressing the CFP-SKL fusion protein to visualize peroxisomes (Perox). The chloroplasts (Chlorop) are visualized by chlorophyll autofluorescence. The top panel shows the bright field (BF). Green and red signals represent CFP and chlorophyll autofluorescence respectively. Bottom panels show the merged image of the green and red signals. Images are displayed as maximal projections of confocal sections. Arrowhead shows dividing chloroplasts. Scale bar 10 μm.

Figure 3
Figure 3

Golgi dictyosomes and chloroplasts distribution inPhyscomitrella patensprotonemata. Bright field and confocal images of 5 distinct zones in caulonemata (A) and chloronemata (B) expressing the YFP-Man fusion protein to visualize Golgi dictyosomes (Golgi). The chloroplasts (Chlorop) are visualized by chlorophyll autofluorescence. The top panel shows the bright field (BF). Green and red signals represent YFP and chlorophyll autofluorescence respectively. Bottom panels show the merged image of the green and red signals. Images are displayed as maximal projections of confocal sections. Arrow and arrowhead show respectively small area deprived of Golgi dictyosomes and dividing chloroplasts. Scale bar 10 μm.

Figure 4
Figure 4

Mitochondria and chloroplasts distribution inPhyscomitrella patensprotonemata. Bright field and confocal images of 5 distinct zones in caulonemata (A) and chloronemata (B) expressing the mEGFP-Cox fusion protein to visualize mitochondria (Mito). The chloroplasts (Chlorop) are visualized by chlorophyll autofluorescence. The top panel shows the bright field (BF). Green and red signals represent mEGFP and chlorophyll autofluorescence respectively. Images are displayed as maximal projections of confocal sections. Scale bar 10 μm.

Figure 5
Figure 5

Organelles density inPhyscomitrella patensprotonemata. Density of chloroplasts (A), peroxisomes (B), Golgi dictyosomes (C) and mitochondria (D) detected in 6 distinct zones of caulonemata and chloronemata with B: Base; N: Nuclear area; To: Tip-oriented area; T: Tip. Results are expressed as the mean value of the number of cells analyzed (chloroplasts, n = 9; peroxisomes, n = 3; Golgi dictyosomes, n = 4 for caulonema and n = 3 for chloronema; Mitochondria, n = 6 for caulonema and n = 3 for chloronema). Error bars indicate the standard error of the mean (samples are statistically different with the following error probabilities: * P < 0.05; ** P < 0.01; *** P < 0.001 by t-test).

Figure 6
Figure 6

Organelles motility in tip gowingPhyscomitrella patenscaulonema. Two representative trajectories of chloroplasts (A), peroxisomes (B), Golgi dictyosomes (C) and mitochondria (D) are shown. Trajectories have been built from time lapse series in which images were acquired at 5 s intervals for 5 min. Scale unit: μm.

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References

    1. Smith LG. Cytoskeletal control of plant cell shape: getting the fine points. Curr Opin Plant Biol. 2003;6:63–73. doi: 10.1016/S1369-5266(02)00012-2. - DOI - PubMed
    1. Geitmann A, Ortega JKE. Mechanics and modeling of plant cell growth. Trends Plant Sci. 2009;14:467–478. doi: 10.1016/j.tplants.2009.07.006. - DOI - PubMed
    1. Szymanski. Plant cells taking shape: new insights into cytoplasmic control. Curr Opin Plant Biol. 2009;12:735–744. doi: 10.1016/j.pbi.2009.10.005. - DOI - PubMed
    1. Schaefer DG, Zrÿd J. Efficient gene targeting in the mossPhyscomitrella patens. Plant J. 1997;11:1195–1206. doi: 10.1046/j.1365-313X.1997.11061195.x. - DOI - PubMed
    1. Bezanilla M, Pan A, Quatrano RS. RNA interference in the mossPhyscomitrella patens. Plant Physiol. 2003;133:470–474. doi: 10.1104/pp.103.024901. - DOI - PMC - PubMed

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