A comparative structural analysis of direct and indirect shoot ...

More documents

Recommendations

Info

Aluminium sensitivity of root cells related to aluminium internalization 4209 Fig. 8. Effect of aluminium on internalization of endocytic marker FM4-64. Control root after 10 min labelling with FM4-64 dye (A). Formation of BFA-induced compartments by 35 lM BFA in FM4-64-labelled roots (B). Treatment with 90 lM aluminium for 90 min did not change considerably the pattern of FM4-64 labelling (C), but it prevented formation of BFA-induced compartments after application of 35 lM BFA (D). Representative of five seedlings per treatment. Bar¼10 lm. induced by aluminium were reversible under the experimental conditions in the recovering cells of both DTZ and PTZ. Consistent with developmentally dependent differences in sensing aluminium, the process of plasma membrane recovery was slower in the cells of the DTZ as compared to those of PTZ. The cellular distribution of aluminium Aluminium either accumulates on the cell surface in the cell walls (Horst et al., 1999; Marienfeld et al., 2000; Wang et al., 2004) or it enters the cells (Tice et al., 1992; Lazof et al., 1994, 1996; Vázquez et al., 1999; Silva et al., 2000; Jones et al., 2006) during exposure to aluminium. However, information about the fate of aluminium associated with cell surfaces during recovery is missing. It is shown here that root cells can restore membrane functions in recovery experiments. The restoration of membrane functions together with the removal of the critical aluminium from the cell surface via its internalization and sequestering within the vacuole may contribute to the recovery of the growth. This scenario has been proposed in the present study. The vacuolar deposits in aluminium-treated maize roots support the tentative conclusion that vacuolar localization of the internalized aluminium might be the mechanism of its intracellular detoxification (Vázquez et al., 1999). Interestingly, the high rate of aluminium internalization was typical only for meristematic cells and for the cells of the distal portion, but not of the proximal portion of the transition zone. Extracellular aluminium is mainly associated with cell wall pectins as was manifested by the correlation between the pectin content in the cell walls and the accumulation of aluminium (Horst et al., 1999; Schmohl and Horst, 2000; Hossain et al., 2006). It is speculated at this early stage that the internalization of aluminium into the cells might be closely related to the endocytosis of cell wall pectins. However, consistent with the pattern of aluminium internalization, internalization and recycling of cell wall pectins is also accomplished only in the cells of the meristem and the distal portion of the transition zone, but not in the region of rapid cell elongation (Baluška et al., 2002, 2005a; Yuet al., 2002; Paciorek et al., 2005; Dhonukshe et al., 2006). Indeed, endocytosis was active during the recovery phase as proved by the internalization of the endocytic marker FM4-64. Endocytosis proceeded in all cells
4210 Illéš et al. Fig. 9. Detection of NO production by DAF-2DA labelling in control root tip (A), root tips treated with 90 lM aluminium for 60 min (B), and 10 lM cPTIO, the NO-scavenger, for 60 min (C). Fluorescence of DAF-2DA is green, FM4-64 is red. Fluorescence intensity (D) and distribution (insert) of DAF-2DA labelling along root developmental zones. Note the disappearance of the NO production peak in DTZ after aluminium treatment. Average intensities of 20 roots per treatment. of the root apex including the PTZ and the elongation zone (see FM4-64 labelling of the tonoplast), although internalization of aluminium was spatially restricted to the pectinrecycling zone (Baluška et al., 2002), and did not occur in the PTZ and the elongation zone. Inside the cells, endosomal-sorting processes might be implicated in releasing the aluminium from the pectin complexes; pectins would be recycled back to the cell wall while aluminium would continue in the endocytic pathway towards the vacuole. Pectin molecules reaching the cell wall may represent a new pool for binding of free and loosely bound apoplastic aluminium and thus support the gradual removal of morinstained apoplastic aluminium during recovery. Supporting data for such endocytic internalization of aluminium come from the presence of aluminium in myelin figures (Vázquez, 2002), which closely resemble the multilamellar endosomes occurring in the pectin internalization pathway (Baluška et al., 2005a). Difficulties with the visualization of these intermediary structures under experimental conditions could be caused by weakening of the morin fluorescent signal intensity. A decrease of the fluorescent signal in the morin detection method after aluminium binding to pectins in vitro was shown by Eticha et al. (2005). However, this finding obtained by both the use of hand sections and
Page 1 and 2:
J. Plant Physiol. 157. 281-289 (200
Page 3 and 4:
Shoot regeneration in opium poppy 2
Page 5 and 6:
Page 7 and 8:
Page 9 and 10: Shoot regeneration in opium poppy 2
Page 11 and 12: M. OVECKA & M. BOBf~K point of view
Page 13 and 14: o "i J
Page 15 and 16: M. OVECKA & M. BOB,4K Fig. 1. Scann
Page 17 and 18: M. OVECKA & M. BOBAK et al. 1997/98
Page 19 and 20: M. OVECKA ,~ M. BOBAK around somati
Page 21 and 22: E Balus"ka et al.: Mitogen-activate
Page 23 and 24: E Balus'ka et al.: Mitogen-activate
Page 25 and 26: E Balugka et al.: Mitogen-activated
Page 27 and 28: Stress MAP kinase SIMK in plant tip
Page 37 and 38: Cell Biology International 27 (2003
Page 39 and 40: J. Samaj et al. / Cell Biology Inte
Page 41 and 42: 52 M. Volgger et al. Fig. 1 Zones o
Page 43 and 44: 54 M. Volgger et al. fluorescence a
Page 45 and 46: 56 M. Volgger et al. The plasma mem
Page 47 and 48: 58 M. Volgger et al. Fig. 6 a-h Aft
Page 49 and 50: 60 M. Volgger et al. other candidat
Page 51 and 52: 62 M. Volgger et al. Ovečka M, Lan
Page 53 and 54: 4202 Illéš et al. cell wall thick
Page 55 and 56: 4204 Illéš et al. Fig. 2. Effect
Page 57 and 58: 4206 Illéš et al. Fig. 5. Changes
Page 59: 4208 Illéš et al. Fig. 7. Interna
Page 63 and 64: 4212 Illéš et al. Bolte S, Talbot
show all

A comparative structural analysis of direct and indirect shoot ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?