Nemesia Root Hair Response to Paper Pulp Substrate for Micropropagation

Agar substrates for in vitro culture are well adapted to plant micropropagation, but not to plant rooting and acclimatization. Conversely, paper-pulp-based substrates appear as potentially well adapted for in vitro culture and functional root production. To reinforce this hypothesis, this study compares in vitro development of nemesia on several substrates. Strong differences between nemesia roots growing in agar or in paper-pulp substrates were evidenced through scanning electron microscopy. Roots developed in agar have shorter hairs, larger rhizodermal cells, and less organized root caps than those growing on paper pulp. In conclusion, it should be noted that in this study, in vitro microporous substrates such as paper pulp lead to the production of similar root hairs to those found in greenhouse peat substrates. Consequently, if agar could be used for micropropagation, rooting, and plant acclimatization, enhancement could be achieved if rooting stage was performed on micro-porous substrates such as paper pulp

Direct Immunological Detection of Wood Cell Wall Polysaccharides after Microwave- Assisted Ionic Liquid Disruption

International audienceWe present here a new cell wall polysaccharide analysis method based on the fast and efficient ionic liquid solubilization of wood samples followed by direct immunological detections of their polysaccharide contents. To reduce both the time and the temperature of the analysis, wood powder samples are first totally disrupted in 1-ethyl-3-methylimidazolium under controlled microwave irradiation. The solubilized extracts are then directly spotted ontonitrocellulose membranes in order to specifically detect their polysaccharide contents with a set of monoclonal antibodies. Compared to the long sequential method classically used for biomass analysis, the technique described in this article allows the simultaneous treatments of higher numbers of smaller samples. It represents an interesting toolkit to rapidly screen various biomass resources for their polysaccharide contents

In vivo activity of recombinant human Lewis fucosyltransferase III in leaves of Nicotiana tabacum

International audienceFucosylation in plants occurs in glycoproteins and polysaccharides but the function of fucosylation is largely unknown. We aimed to analyze the effects of over-expression of human fucosyltransferase III (hFucT III) on in vivo N-glycan accumulation in tobacco plant leaves and focused on comparing the amount of Lewis a (Lea)-epitope accumulation in transgenic and in wild-type plants. Fucosyltransferase assays, Western blot and mass spectrometry were used to identify, quantify and analyse Lea N-glycans. We found that constitutive overexpression of hFucT III activity had no effect on Lea complex type N-glycans accumulation. Our results suggest that tobacco recombinant hFucT III acts more as a hydrolase than as a transferase

Effects of humic substances on the rooting and development of woody plant cuttings.

International audienceHumic substances are known to be natural product that could be used as an alternative to artificial fertilizer. The aim of this work was to study the effects of a commercial product containing humic substances, Humyk-Fer (Duclos International), on woody cutting-plant development (Lantana camara). Infrared, fluorescence, atomic absorption and 13C-NMR spectrometry's analysis indicate that Humyk-Fer is com¬posed respectively of 73% and 27% of humic (HA) and fulvic (FA) acids but equally present a high content of metal ions (Fe2+, K+, Na+). The biological effects of Humyk-Fer were then investigated on plant development. Different levels (0, 1, 2 and 4% (v/v)) and various numbers of treatments (1 and 2) were tested in greenhouse for L. camara. First results show that Humyk-Fer drastically increase the growth (170 x), but also reduce the delay of floral transition of L. camara. In addition, a strong reduc¬tion of ferric chlorosis occurred on treated plants. Complementary studies were then conducted to determine the respective functions of HA and FA on growth stimulation as on floral development. In these experiments, agronomic parameters were coupled with molecular analysis of an homeotic MADS-box AGAMOUS-like (AGL) genes. Preliminary results seem to suggest that AGL gene is up-regulated by humic acid treatment suggesting that low amount of humic substances increase plant organo¬genesis, and probably flower development

NaCl effect on the distribution of wall ingrowth polymers and arabinogalactan proteins in type A transfer cells of Medicago sativa Gabès leaves

International audienceWe studied the distribution of wall ingrowth (WI) polymers by probing thin sections of companion cells specialized as transfer cells in minor veins of Medicago sativa cv Gabès blade with affinity probes and antibodies specific to polysaccharides and glycoproteins. The wall polymers in the controls were similar in WIs and in the primary wall but differently distributed. The extent of labeling in these papillate WIs differed for JIM5 and JIM7 homogalacturonans but was in the same range for LM5 and LM6 rhamnogalacturonans and xyloglucans. These data show that WI enhancement probably requires arabinogalactan proteins (JIM8) mainly localized on the outer part of the primary wall and WIs. By comparison, NaCl-treated plants exhibited cell wall polysaccharide modifications indicating (1) an increase in unesterified homogalacturonans (JIM5), probably implicated in Na+ binding and/or polysaccharide network interaction for limiting turgor variations in mesophyll cells; (2) enhancement of the xyloglucan network with an accumulation of fucosylated xyloglucans (CCRC-M1) known to increase the capacity of cellulose binding; and (3) specific recognition of JIM8 arabinogalactan proteins that could participate in both wall enlargement and cohesion by increasing the number of molecular interactions with the other polymers. In conclusion, the cell wall polysaccharide distribution in enlarged WIs might (1) participate in wall resistance to sequestration of Na+, allowing a better control of hydric homeostasis in mesophyll cells to maintain metabolic activity in source leaves, and (2) maintain tolerance of M. sativa to NaCl

Cloning and expression analysis of a wood-associated xylosidase gene (PtaBXL1) in poplar tension wood.

International audienceIn stems of woody angiosperms responding to mechanical stress, imposed for instance by tilting the stem or formation of a branch, tension wood (TW) forms above the affected part, while anatomically distinct opposite wood (OW) forms below it. In poplar TW the S3 layer of the secondary walls is substituted by a "gelatinous layer" that is almost entirely composed of cellulose and has much lower hemicellulose contents than unstressed wood. However, changes in xylan contents (the predominant hemicelluloses), their interactions with other wall components and the mechanisms involved in TW formation have been little studied. Therefore, in the study reported here we determined the structure and distribution of xylans, cloned the genes encoding the xylan remodeling enzymes beta-xylosidases (PtaBXLi), and examined their expression patterns during tension wood, normal wood and opposite wood xylogenesis in poplar. We confirm that poplar wood xylans are substituted solely by 4-O-methylglucuronic acid in both TW and OW. However, although glucuronoxylans are strongly represented in both primary and secondary layers of OW, no 4-O-methylGlcA xylan was found in G-layers of TW. Four full-length BXL cDNAs encoding putative beta-xylosidases were cloned. One, PtaBXL1, for which xylosidase activity was confirmed by heterologous expression in Escherichia coli, exhibited a wood-specific expression pattern in TW. In conclusion, xylan as PtaBXL1, encoding beta4-xylosidase activity, are down-regulated in TW

Cell wall thickening in two Ulva species in response to heavy metal marine pollution

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