Structural changes induced by NaCl in companion and transfer cells of Medicago sativa blades

Boughanmi, Néziha; Michonneau, Philippe; Verdus, Marie‐Claire; Piton, Françoise; Ferjani, Ezzedine El; Bizid, Essia; Fleurat‐Lessard, Pierrette

doi:10.1007/s00709-002-0043-6

Cited by 16 publications

(13 citation statements)

References 29 publications

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“…Recently, a CC expressed metal binding protein, NaKR1, was found to reduce sodium accumulation in leaves by upregulating phloem loading and export of sodium (Tian et al, 2010). The NaKR1 function maps onto earlier findings that exposure of Trifolium alexandrium (Winter, 1982) and Medicago sativa (Boughanmi et al, 2003), to elevated sodium levels induced CCs of leaf transport phloem to undergo trans -differentiation to a TC morphology. In addition, observed salt-induced increases in levels of unmethylated pectins, fucosylated xyloglucans, and arabinogalactans in wall ingrowths of CC/TCs might act to buffer free sodium levels in leaf apoplasms (Boughanmi et al, 2010).…”

Section: Functional Role Of Transfer Cells In Phloem Transportmentioning

confidence: 59%

Intersection of transfer cells with phloem biology—broad evolutionary trends, function, and induction

Andriunas¹,

Zhang²,

Xia³

et al. 2013

Front. Plant Sci.

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Transfer cells (TCs) are ubiquitous throughout the plant kingdom. Their unique ingrowth wall labyrinths, supporting a plasma membrane enriched in transporter proteins, provides these cells with an enhanced membrane transport capacity for resources. In certain plant species, TCs have been shown to function to facilitate phloem loading and/or unloading at cellular sites of intense resource exchange between symplasmic/apoplasmic compartments. Within the phloem, the key cellular locations of TCs are leaf minor veins of collection phloem and stem nodes of transport phloem. In these locations, companion and phloem parenchyma cells trans-differentiate to a TC morphology consistent with facilitating loading and re-distribution of resources, respectively. At a species level, occurrence of TCs is significantly higher in transport than in collection phloem. TCs are absent from release phloem, but occur within post-sieve element unloading pathways and particularly at interfaces between generations of developing Angiosperm seeds. Experimental accessibility of seed TCs has provided opportunities to investigate their inductive signaling, regulation of ingrowth wall formation and membrane transport function. This review uses this information base to explore current knowledge of phloem transport function and inductive signaling for phloem-associated TCs. The functional role of collection phloem and seed TCs is supported by definitive evidence, but no such information is available for stem node TCs that present an almost intractable experimental challenge. There is an emerging understanding of inductive signals and signaling pathways responsible for initiating trans-differentiation to a TC morphology in developing seeds. However, scant information is available to comment on a potential role for inductive signals (auxin, ethylene and reactive oxygen species) that induce seed TCs, in regulating induction of phloem-associated TCs. Biotic phloem invaders have been used as a model to speculate on involvement of these signals.

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Section: Functional Role Of Transfer Cells In Phloem Transportmentioning

confidence: 59%

Intersection of transfer cells with phloem biology—broad evolutionary trends, function, and induction

Andriunas¹,

Zhang²,

Xia³

et al. 2013

Front. Plant Sci.

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“…Na + accumulation into vacuoles may contribute to osmotic adjustment, since it is the least demanding form of physiological or biochemical adjustment (consuming only 3-4 moles of ATP per mole of ion in comparison with 30-50 moles of ATP for the synthesis of organic solutes such as proline or sucrose) (Raven 1985). Low leaf accumulation and higher stem Na + content could also indicate the export of this toxic ion by phloem in M. ciliaris lines, as shown in Medicago sativa, in which transfer cells play a crucial role at controlling nutrient and ion fluxes (Boughanmi et al 2003).…”

Section: Discussionmentioning

confidence: 97%

Variability in the response of six genotypes of N2-fixing Medicago ciliaris to NaCl

et al. 2011

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Genotypic variability was assessed within six Medicago ciliaris genotypes growing symbiotically with Sinorhizobium medicae in order to identify physiological criteria (growth, ion content, and plant health) associated with salt tolerance. Response to salt stress depended on the line and the level of salt. Two lines with lower dry biomass under non-saline conditions (TNC 1.8 from a semi-arid area and TNC 10.8 from a sub-humid area), were more tolerant to NaCl, whereas the most productive lines (TNC 11.5 and TNC 11.9 from a humid bioclime) were more sensitive in terms of growth and nitrogen fixation. Susceptibility of symbiotic nitrogen fixation to saline stress was not associated with a higher accumulation of Na + in nodules, since the most tolerant lines TNC 1.8 and TNC 10.8 accumulated the highest Na + amount in nodules. Leaf area and net photosynthate assimilation rate were conserved in line TNC 1.8 and to a lesser extent in line TNC 10.8 potentially owing to a greater ability to protect aerial organs and nodules from Na + damage and to insure a better supply of leaves with nitrogen. Our results suggest that nodule growth and number and nodule Na + content should not be used as selection tools for tolerance or susceptibility, since two of the tested lines maintained consistent growth in spite of reduced nodule and high Na + content. Instead, the most reliable physiological indicators for tolerance appear to be consistent growth (i.e., no growth changes) and reduced leaf Na + accumulation with increasing concentrations of NaCl.

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“…Moreover, tetraploidy confers a considerable phenotypical plasticity to this cultivar, and adaptative mechanisms are hypothesized to develop in response to long-term high NaCl exposure. The effect of a 150 mM NaCl treatment on the ultrastructure of leaf veins in this cultivar of considerable agronomic interest has been reported previously (Boughanmi et al, 2003). Changes induced by salt differed between the minor and the main veins of the upper and lower exporting leaves.…”

Section: Introductionmentioning

confidence: 88%

“…Particularly in the chloroplasts, an accumulation of starch might result from a reduced activity of the enzymes involved in its degradation (Salama et al, 1994) and/or an alteration of companion cells, involved in assimilate collection in minor veins (Boughanmi et al, 2003). The damage of thylakoids and grana is thought to be the consequence of saltinduced oxidative stress (Mitsuya et al, 2000).…”

Section: Nacl Accelerated Leaf Senescencementioning

confidence: 99%

Adaptation of Medicago sativa cv. Gabès to long‐term NaCl stress

Boughanmi¹,

Michonneau

Daghfous

et al. 2005

Z. Pflanzenernähr. Bodenk.

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The perennial Medicago sativa cv. Gabs is widely grown on saline soils in Tunisian oases. The mechanisms by which this NaCl-tolerant cultivar maintains a positive growth balance were analyzed. In this plant of considerable agronomic interest, biochemical analyses were conducted in order to study the effects of salinity on mature leaves. Free-radical detoxification mechanisms and changes induced by the accumulation of reactive oxygen species (ROS) in response to the NaCl stress were compared between the upper (young) and lower (old) carbohydrate source leaves. Long-term NaCl (150 mM) treatment significantly reduced the size of source leaves supporting growth. Salinity damage was greater in the lower than in the upper leaves. This damage was associated with a high Na + : K + ratio and a decrease in the activity of H 2 O 2 -scavenging enzymes, leading to lipid peroxidation. In lower source leaves that were mainly affected by ionic stress, superoxide dismutase (SOD) was overexpressed and guaiacol peroxidase (GPX) activity increased. In contrast, in upper source leaves that were mainly exposed to water deficit, catalase and ascorbate peroxidase (APX) activities increased whereas GPX activity was unchanged. The upper source leaves maintained adequate ionic and water status and an efficient ROS detoxification, allowing sinks to be supplied with photoassimilates and maintaining a positive growth balance in this cultivar of alfalfa.

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Structural changes induced by NaCl in companion and transfer cells of Medicago sativa blades

Cited by 16 publications

References 29 publications

Intersection of transfer cells with phloem biology—broad evolutionary trends, function, and induction

Intersection of transfer cells with phloem biology—broad evolutionary trends, function, and induction

Variability in the response of six genotypes of N2-fixing Medicago ciliaris to NaCl

Adaptation of Medicago sativa cv. Gabès to long‐term NaCl stress

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