Recovery of heat shock-triggered released apoplastic Ca2+ accompanied by pectin methylesterase activity is required for thermotolerance in soybean seedlings

Synthesis of heat shock proteins (HSPs) in response to heat shock (HS) is essential for thermotolerance. The effect of a Ca2+ chelator, EGTA, was investigated before a lethal HS treatment in soybean (Glycine max) seedlings with acquired thermotolerance induced by preheating. Such seedlings became non-thermotolerant with EGTA treatment. The addition of Ca2+, Sr2+ or Ba2+ to the EGTA-treated samples rescued the seedlings from death by preventing the increased cellular leakage of electrolytes, amino acids, and sugars caused by EGTA. It was confirmed that EGTA did not affect HSP accumulation and physiological functions but interfered with the recovery of HS-released Ca2+ concentration which was required for thermotolerance. Pectin methylesterase (PME, EC 3.1.1.11), a cell wall remodelling enzyme, was activated in response to HS, and its elevated activity caused an increased level of demethylesterified pectin which was related to the recovery of the HS-released Ca2+ concentration. Thus, the recovery of HS-released Ca2+ in Ca2+-pectate reconstitution through PME activity is required for cell wall remodelling during HS in soybean which, in turn, retains plasma membrane integrity and co-ordinates with HSPs to confer thermotolerance

Loss of Cofilin 1 Disturbs Actin Dynamics, Adhesion between Enveloping and Deep Cell Layers and Cell Movements during Gastrulation in Zebrafish

During gastrulation, cohesive migration drives associated cell layers to the completion of epiboly in zebrafish. The association of different layers relies on E-cadherin based cellular junctions, whose stability can be affected by actin turnover. Here, we examined the effect of malfunctioning actin turnover on the epibolic movement by knocking down an actin depolymerizing factor, cofilin 1, using antisense morpholino oligos (MO). Knockdown of cfl1 interfered with epibolic movement of deep cell layer (DEL) but not in the enveloping layer (EVL) and the defect could be specifically rescued by overexpression of cfl1. It appeared that the uncoordinated movements of DEL and EVL were regulated by the differential expression of cfl1 in the DEL, but not EVL as shown by in situ hybridization. The dissociation of DEL and EVL was further evident by the loss of adhesion between layers by using transmission electronic and confocal microscopy analyses. cfl1 morphants also exhibited abnormal convergent extension, cellular migration and actin filaments, but not involution of hypoblast. The cfl1 MO-induced cell migration defect was found to be cell-autonomous in cell transplantation assays. These results suggest that proper actin turnover mediated by Cfl1 is essential for adhesion between DEL and EVL and cell movements during gastrulation in zebrafish

Revealing the Functions of the Transketolase Enzyme Isoforms in Rhodopseudomonas palustris Using a Systems Biology Approach

BACKGROUND: Rhodopseudomonas palustris (R. palustris) is a purple non-sulfur anoxygenic phototrophic bacterium that belongs to the class of proteobacteria. It is capable of absorbing atmospheric carbon dioxide and converting it to biomass via the process of photosynthesis and the Calvin-Benson-Bassham (CBB) cycle. Transketolase is a key enzyme involved in the CBB cycle. Here, we reveal the functions of transketolase isoforms I and II in R. palustris using a systems biology approach. METHODOLOGY/PRINCIPAL FINDINGS: By measuring growth ability, we found that transketolase could enhance the autotrophic growth and biomass production of R. palustris. Microarray and real-time quantitative PCR revealed that transketolase isoforms I and II were involved in different carbon metabolic pathways. In addition, immunogold staining demonstrated that the two transketolase isoforms had different spatial localizations: transketolase I was primarily associated with the intracytoplasmic membrane (ICM) but transketolase II was mostly distributed in the cytoplasm. Comparative proteomic analysis and network construction of transketolase over-expression and negative control (NC) strains revealed that protein folding, transcriptional regulation, amino acid transport and CBB cycle-associated carbon metabolism were enriched in the transketolase I over-expressed strain. In contrast, ATP synthesis, carbohydrate transport, glycolysis-associated carbon metabolism and CBB cycle-associated carbon metabolism were enriched in the transketolase II over-expressed strain. Furthermore, ATP synthesis assays showed a significant increase in ATP synthesis in the transketolase II over-expressed strain. A PEPCK activity assay showed that PEPCK activity was higher in transketolase over-expressed strains than in the negative control strain. CONCLUSIONS/SIGNIFICANCE: Taken together, our results indicate that the two isoforms of transketolase in R. palustris could affect photoautotrophic growth through both common and divergent metabolic mechanisms

Comparative Study on the Stinging Trichomes and Some Related Epidermal Structures in the Leaves of Dendrocnide meyeniana, Girardinia diversifolia, and Urtica thunbergiana

In this study, the morphology and distribution of the stinging trichomes and the related epidermal structures in the mature leaves of Dendrocnide meyeniana, Girardinia diversifolia, and Urtica thunbergiana are compared. On the adaxial and abaxial leaf surfaces, stinging trichomes, glandular, and non-glandular (hispid and pustulate) were observed. Among these studied species, the stinging trichome of Dendrocnide meyeniana is the shortest, but the density on the adaxial surface is the highest. In Girardinia diversifolia, the stinging trichomes are the longest, but the density is the lowest. The major elements of stinging cells of all the studied plants are silicon and calcium. In Dendrocnide meyeniana, the average silicon/calcium ratio is the highest, while the lowest silicon/calcium ratio was found in the stinging cells located on the veins of abaxial surface in Urtica thunbergiana. In Girardinia diversifolia, the amount and surrounding area of pedestal cells are the highest while in Dendrocnide meyeniana, however, are the lowest. On the leaf surface of Urtica thunbergiana, not any hydathode was observed, while pearl glands were only found in the leaves of Dendrocnide meyeniana. Calcium carbonate and oxalate depositions were found in all the studied stinging species

Various Microscopic Methods for Investigating the Venuloid Idioblasts of Pteris grevilleana Wall.

Venuloid idioblasts are vein-like structures. In Pteris, they are long epidermal cells with very thick cell walls. In this study, venuloid idioblasts of Pteris grevilleana were investigated with various light microscopic (LM) and scanning electron microscopic (SEM) techniques and the main purposes of these microscopic techniques are summarized and discussed. To investigate the morphology and distribution of venuloid idioblasts, partial polarization LM technique and cryo-tabletop-SEM technique were used. The idioblasts had lobed margins, acute or round ends, and could be found on both upper and lower epidermis of fertile fronds and sterile fronds. They are distributed on veins, interveinal regions, and leaf margins, but not on costules, costae, and false indusia. By using histochemical staining and SEM with energy dispersive X-ray spectrometer (EDS), it was confirmed that the idioblasts contained silicon. In addition, the venuloid-idioblast-like silica bodies were extracted by wet oxidation method. These indicate that the venuloid indioblast in P. grevilleana is a kind of spicular cell (long epidermal cells containing silica bodies, which are found in Adiantoids and Vittarioids)

Extracellular Pgk1 interacts neural membrane protein enolase-2 to improve the neurite outgrowth of motor neurons

Abstract Understanding the molecular interaction between ligand and receptor is important for providing the basis for the development of regenerative drugs. Although it has been reported that extracellular phosphoglycerate kinase 1 (Pgk1) can promote the neurite outgrowth of motoneurons, the Pgk1-interacting neural receptor remains unknown. Here we show that neural membranous Enolase-2 exhibits strong affinity with recombinant Pgk1-Flag, which is also evidently demonstrated by immunoelectron microscopy. The 325th-417th domain of Pgk1 interacts with the 405th-431st domain of Enolase-2, but neither Enolase-1 nor Enolase-3, promoting neurite outgrowth. Combining Pgk1 incubation and Enolase-2 overexpression, we demonstrate a highly significant enhancement of neurite outgrowth of motoneurons through a reduced p-P38-T180/p-Limk1-S323/p-Cofilin signaling. Collectively, extracellular Pgk1 interacts neural membrane receptor Enolase-2 to reduce the P38/Limk1/Cofilin signaling which results in promoting neurite outgrowth. The extracellular Pgk1-specific neural receptor found in this study should provide a material for screening potential small molecule drugs that promote motor nerve regeneration