The structure, function, and biosynthesis of plant cell wall pectic polysaccharides.

Anthocyanins and betalains play important roles both in plant physiology, visual attraction for pollinators and seed dispersers, but also in food mainly defining its aesthetic value. Since anthocyanin and betalain structures allow to predict only part of their appearance, additional chemical and anatomical functions are required to modulate the appearance of plants and coloured food. Physiological effects that the same pigments exert in plants are supposedly similar to those which they show in humans following ingestion of coloured food. Therefore, anthocyanins and betalains both in fresh and also processed fruit and vegetables serve two functions: They improve the overall appearance, but also contribute to consumers' health and well-being.

Functional properties of anthocyanins and betalains in plants, food, and in human nutrition

How genes paint flowers and seeds

Potato tuber tissue discs, which were aged after wounding in order to acquire hypersensitive reactivity, reduced extracellular cytochrome c and nitroblue tetrazolium (NBT) following inoculation with an incompatible, but not compatible, race of Phytophthora infestans . The cytochrome c -reducing activity rapidly increased from l to 4 h after inoculation along with an increase in the percentage of hypersensitively dead cells, and then decreased from the time when most of the penetrated cells had died. A localized activation of NBT reduction around invading hyphae of the incompatible, but not those of the compatible, race was observed at early stages of penetration before cell death. The reductive activity of the discs was also elicited by treatment with a hypersensitivity-eliciting substance, hyphal wall components of the fungus. Superoxide dismutase (SOD), an enzyme catalysing the conversion of the superoxide anion (O 2 − ) to H 2 O 2 and O 2 inhibited the enhanced reducing activity of the discs when added to the assay solution, indicating that cytochrome c and NBT may be reduced by O 2 − generated from the discs. Pre-infectional, vacuum infiltration of the discs with a solution containing SOD significantly delayed the occurrence of hypersensitive cell death caused by infection with the incompatible race as well as the accumulation of phytoalexin. Application of SH-binding reagents and NADP + , but not respiratory inhibitors, inhibited the elicitation of the reducing activity caused by infection with the incompatible race. These results indicate that an O 2 − -generating system may be activated in potato tissues during the incompatible interaction induced by invading fungi or fungal wall components, and also that the generation of O 2 − may be involved during hypersensitive cell death as a trigger of the sequence of resistance reactions.

Involvement of superoxide anion generation in the hypersensitive response of potato tuber tissues to infection with an incompatible race of Phytophthora infestans and to the hyphal wall components

Ionic stress is one of the most important components of salinity and is brought about by excess Na+ accumulation, especially in the aerial parts of plants. Since Na+ interferes with K+ homeostasis, and especially given its involvement in numerous metabolic processes, maintaining a balanced cytosolic Na+/K+ ratio has become a key salinity tolerance mechanism. Achieving this homeostatic balance requires the activity of Na+ and K+ transporters and/or channels. The mechanism of Na+ and K+ uptake and translocation in glycophytes and halophytes is essentially the same, but glycophytes are more susceptible to ionic stress than halophytes. The transport mechanisms involve Na+ and/or K+ transporters and channels as well as non-selective cation channels. Thus, the question arises of whether the difference in salt tolerance between glycophytes and halophytes could be the result of differences in the proteins or in the expression of genes coding the transporters. The aim of this review is to seek answers to this question by examining the role of major Na+ and K+ transporters and channels in Na+ and K+ uptake, translocation and intracellular homeostasis in glycophytes. It turns out that these transporters and channels are equally important for the adaptation of glycophytes as they are for halophytes, but differential gene expression, structural differences in the proteins (single nucleotide substitutions, impacting affinity) and post-translational modifications (phosphorylation) account for the differences in their activity and hence the differences in tolerance between the two groups. Furthermore, lack of the ability to maintain stable plasma membrane (PM) potentials following Na+-induced depolarization is also crucial for salt stress tolerance. This stable membrane potential is sustained by the activity of Na+/H+ antiporters such as SOS1 at the PM. Moreover, novel regulators of Na+ and K+ transport pathways including the Nax1 and Nax2 loci regulation of SOS1 expression and activity in the stele, and haem oxygenase involvement in stabilizing membrane potential by activating H+-ATPase activity, favorable for K+ uptake through HAK/AKT1, have been shown and are discussed.

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The Role of Na+ and K+ Transporters in Salt Stress Adaptation in Glycophytes.

/pdf/cause-of-blue-petal-colour-2g1705prd0.pdf

Cause of blue petal colour

Petal color change in morning glory Ipomoea tricolor cv. Heavenly Blue, from red to blue, during the flower-opening period is due to an unusual increase in vacuolar pH (pHv) from 6.6 to 7.7 in colored epidermal cells. We clarified that this pHv increase is involved in tonoplast-localized Na+/H+ exchanger (NHX). However, the mechanism of pHv increase and the physiological role of NHX1 in petal cells have remained obscure. In this study, synchrony of petal-color change from red to blue, pHv increase, K+ accumulation, and cell expansion growth during flower-opening period were examined with special reference to ItNHX1. We concluded that ItNHX1 exchanges K+, but not Na+, with H+ to accumulate an ionic osmoticum in the vacuole, which is then followed by cell expansion growth. This function may lead to full opening of petals with a characteristic blue color.

Synchrony between flower opening and petal-color change from red to blue in morning glory, Ipomoea tricolor cv. Heavenly Blue

Elongation of plant stem is governed by two simultaneous processes: irreversible yielding of the cell wall and uptake of water. Among many candidates for the parameters that redulate and/or restrict growth, we focused on the mechanical properties of the cell wall and determined those parameters that govern of IAA-induced growth by means of the pressure-jump method combined with the pressure-probe technique

Auxin changes both the extensibility and the yield threshold of the cell wall of vigna hypocotyls

The role of electrogenic xylem pumps in K+ absorption from the zylem of Vigna unguiculata: the effects of auxin and fusicoccin

cDNA for yieldin of Vigna unguiculata L. was cloned with reverse transcriptase-polymerase chain reaction using synthetic oligonucleotides as primers. The primers were designed on the basis of the N-terminal amino acid sequence of the yieldins isolated from the wall preparation of cowpea hypocotyls. The 1.2 kbp cDNA for yieldin contained an open reading frame of 981 base pairs, encoding 327 amino acids including 23 amino acids as a putative signal sequence. An homology search of the deduced amino acid sequence revealed that the yieldin was homologous to acidic class III endochitinases (EC 3.2.1.14) and concanavalin B. A cDNA fragment containing the yieldin-coding region was introduced to Escherichia coli cells using an expression vector to express the recombinant protein. The recombinant yieldin was obtained from the recombinant E. coli and its effect on the wall mechanical properties was examined by reconstitution experiments. The recombinant yieldin fully restored the acid-induced change of the yield threshold tension (y) of heat denatured glycerinated hollow cylinders (GHCs) of cowpea hypocotyls. Northern hybridization analysis revealed that the yieldin mRNA was expressed mainly in the rapid and moderate elongation region of the etiolated hypocotyl of Vigna unguiculata L.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-3040.2000.00526.x

Kiyoshi Katou

Papers

Cause of blue petal colour

Synchrony between flower opening and petal-color change from red to blue in morning glory, Ipomoea tricolor cv. Heavenly Blue

Auxin changes both the extensibility and the yield threshold of the cell wall of vigna hypocotyls

The role of electrogenic xylem pumps in K+ absorption from the zylem of Vigna unguiculata: the effects of auxin and fusicoccin

Molecular cloning of yieldins regulating the yield threshold of cowpea cell walls: cDNA cloning and characterization of recombinant yieldin.