Chlorogenic acids (CGAs) and the biopolymer lignin are both products of the phenylpropanoid pathway. Whereas CGAs have been reported to play a role during stress responses, lignin is a major ...component of secondary cell walls, providing physical strength and hydrophobicity to supportive and water-conducting tissues. Because the chemical structure of CGAs largely resembles those of some lignin intermediates and because CGAs can be converted back to hydroxycinnamoyl-CoAs in vitro, CGAs have been considered authentic intermediates of the lignin biosynthetic pathway. However, it is still unclear whether and how the CGA pool can be channeled towards the production of lignin monomers in response to developmental or environmental signals. Comprehensive studies on the catalytic activity of recombinant enzymes together with functional characterizations in planta have been very useful in understanding the potential interdependence between these two metabolic routes. Here we present the current understanding on CGA metabolism and discuss the biochemical and molecular evidence of the metabolic re-routing of CGAs towards lignin.
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•Chlorogenic acids (CGAs) and lignin are products of the phenylpropanoid pathway.•The chemical structure of CGAs largely resembles those of some lignin intermediates.•It is still unclear whether and how CGAs are channeled towards lignin biosynthesis.•Caffeoyl shikimate esterase might be the missing link between CGAs and lignin.
Lignin is a polymer of phenylpropanoid compounds formed through a complex biosynthesis route, represented by a metabolic grid for which most of the genes involved have been sequenced in several ...plants, mainly in the model-plants Arabidopsis thaliana and Populus. Plants are exposed to different stresses, which may change lignin content and composition. In many cases, particularly for plant-microbe interactions, this has been suggested as defence responses of plants to the stress. Thus, understanding how a stressor modulates expression of the genes related with lignin biosynthesis may allow us to develop study-models to increase our knowledge on the metabolic control of lignin deposition in the cell wall. This review focuses on recent literature reporting on the main types of abiotic and biotic stresses that alter the biosynthesis of lignin in plants.
Key message
Eucalypt seedlings differently modulate root morphology in response to phosphorus availability, with changes in the length or density of root hairs being more common that changes in root ...length.
Phosphorus (P) is an essential nutrient for plant growth and development and thus can restrict biomass accumulation when it is at low levels in the soil. Eucalypts cover large areas of planted forests in the world, including regions with naturally low P availability. This study was conducted to evaluate the morphological changes in the roots of seedlings of five eucalypt species:
Eucalyptus acmenoides
,
E. globulus
,
E. grandis
,
E. tereticornis
and
Corymbia maculata
in response to low P concentration. Seedlings were grown in pots with vermiculite and received a nutrient solution of low (25 μM), and sufficient concentration (500 μM) of P. Root hair length and density were evaluated in secondary root segments, and the production of plant biomass and P concentration in the shoots were determined. The species modulated root morphology differently in response to P limitation.
E. tereticornis
showed the lowest plasticity of these morphological traits in response to P concentration. The total root length increased in some species, but changes in the length and/or density of root hairs were the commonest response to low P concentration. P concentrations in the shoots and biomass production were not related to increase of root length or root hair density and length.
Lignin is a heterogeneous aromatic polymer responsible for cell wall stiffness and protection from pathogen attack. However, lignin represents a bottleneck to biomass degradation due to its ...recalcitrance related to the natural cell wall resistance to release sugars for fermentation or further processing. A biological approach involving genetics and molecular biology was used to disrupt lignin pathway synthesis and decrease lignin deposition. Here, we imaged three-dimensional fragments of the petioles of wild type and C4H lignin mutant Arabidopsis thaliana plants by synchrotron cryo-ptychography. The three-dimensional images revealed the heterogeneity of vessels, parenchyma, and fibre cell wall morphologies, highlighting the relation between disturbed lignin deposition and vessel implosion (cell collapsing and obstruction of water flow). We introduce a new parameter to accurately define cell implosion conditions in plants, and we demonstrate how cryo-ptychographic X-ray computed tomography (cryo-PXCT) provides new insights for plant imaging in three dimensions to understand physiological processes.
Wood contains a large amount of air, even in functional xylem. Air embolisms in the xylem affect water transport and can determine plant growth and survival. Embolisms are usually estimated with ...laborious hydraulic methods, which can be prone to several artefacts.
Here, we describe a new method for estimating embolisms that is based on air flow measurements of entire branches. To calculate the amount of air flowing out of the branch, a vacuum was applied to the cut bases of branches under different water potentials.
We first investigated the source of air by determining whether it came from inside or outside the branch. Second, we compared embolism curves according to air flow or hydraulic measurements in 15 vessel- and tracheid-bearing species to test the hypothesis that the air flow is related to embolism.
Air flow came almost exclusively from air inside the branch during the 2.5-min measurements and was strongly related to embolism. We propose a new embolism measurement method that is simple, effective, rapid and inexpensive, and that allows several measurements on the same branch, thus opening up new possibilities for studying plant hydraulics.
Deposition of lignin in four species of Saccharum Llerena, Juan Pablo Portilla; Figueiredo, Raquel; Brito, Michael Dos Santos ...
Scientific reports,
04/2019, Letnik:
9, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We used primers designed on conserved gene regions of several species to isolate the most expressed genes of the lignin pathway in four Saccharum species. S. officinarum and S. barberi have more ...sucrose in the culms than S. spontaneum and S. robustum, but less polysaccharides and lignin in the cell wall. S. spontaneum, and S. robustum had the lowest S/G ratio and a lower rate of saccharification in mature internodes. Surprisingly, except for CAD, 4CL, and CCoAOMT for which we found three, two, and two genes, respectively, only one gene was found for the other enzymes and their sequences were highly similar among the species. S. spontaneum had the highest expression for most genes. CCR and CCoAOMT B presented the highest expression; 4CL and F5H showed increased expression in mature tissues; C3H and CCR had higher expression in S. spontaneum, and one of the CADs isolated (CAD B) had higher expression in S. officinarum. The similarity among the most expressed genes isolated from these species was unexpected and indicated that lignin biosynthesis is conserved in Saccharum including commercial varieties Thus the lignin biosynthesis control in sugarcane may be only fully understood with the knowledge of the promotor region of each gene.
Drought is considered the major abiotic stress limiting crop productivity. This study seeks to identify proteins involved in the drought response in sugarcane stems submitted to drought stress. The ...integration of nuclei enrichment sample preparation with the shotgun proteomic approach results in great coverage of the sugarcane stem proteome with 5381 protein groups identified. A total of 1204 differentially accumulated proteins are detected in response to drought, among which 586 and 618 are increased and reduced in abundance, respectively. A total of 115 exclusive proteins are detected, being 41 exclusives of drought‐stressed plants and 74 exclusives of control plants. In the control plants, most of these proteins are related to cell wall metabolism, indicating that drought affects negatively the cell wall metabolism. Also, 37 transcription factors (TFs) are identified, which are low abundant nuclear proteins and are differentially accumulated in response to drought stress. These TFs are associated to protein domains such as leucine‐rich (bZIP), C2H2, NAC, C3H, LIM, Myb‐related, heat shock factor (HSF) and auxin response factor (ARF). Increased abundance of chromatin remodeling and RNA processing proteins are also observed. It is suggested that these variations result from an imbalance of protein synthesis and degradation processes induced by drought.
Urochloa in Tropical Agroecosystems Baptistella, João Leonardo Corte; de Andrade, Sara Adrián López; Favarin, José Laércio ...
Frontiers in sustainable food systems,
08/2020, Letnik:
4
Journal Article
Recenzirano
Odprti dostop
Increasing biodiversity is an important issue in more secure and sustainable agriculture. Diversified systems are more resilient to climate change, environmental stresses and enhance soil health, ...nutrient cycling and nutrient use efficiency. In tropical agroecosystems, cover crops and intercrops are an alternative toward a more diverse and sustainable production. Urochloa spp. (syn. Brachiaria spp.) are perennial grasses, known for their high biomass production. They are commonly used as cover and companion crops in conservation agriculture in the tropics and the residues left in the field after cutting protect the soil and provide nutrient to the next crop cycle or intercropped culture. Urochloa species roots are vigorous, abundant and deep, as opposed to the more shallow and scarce roots of common crops. These traits contribute to carbon sequestration, soil organic matter stabilization and nutrient cycling. Urochloa roots also improve soil physical characteristics and influence soil nutrient dynamics, reducing nutrient losses and enhancing cycling, what is key to achieve greater nutrient use efficiency in agriculture. For instance, Urochloa root exudates can reduce nitrogen losses by denitrification and leaching through a process called biological nitrification inhibition; root exudates can mobilize recalcitrant phosphorus from soils and make it available for plant uptake; the deep roots of these grasses have the potential to recover nutrients that are virtually lost away from the root zone of other crops. This review compiles scientific progress regarding the introduction of Urochloa in agroecosystems, mainly on the aspects related to the contribution to more secure and sustainable agriculture.
Hypericum brasiliense is a medicinal herb containing several compounds with important pharmacological activity. In this study, we investigated the effects of water stress (waterlogging and drought) ...and temperature (low and high, constant and alternate) on the content of betulinic acid and phenolic compounds (quercetin, rutin, 1,5-dihydroxyxanthone, isouliginosin
B) in this species. In general, the water stress increased the levels of all of the compounds analyzed, particularly some of the phenolic compounds. On the other hand, the responses to alternating temperatures varied according to the compound. The results for plants kept in growth chambers indicated that low light intensity might have influenced the levels of the compounds. There was also a reallocation of carbon, with water-stressed plants showing a reduction in growth while the levels of the compounds increased. In the temperature treatments, such an increase was evident only for the phenolic compounds.
Phosphorus (P) is a vital nutrient for plant growth. P availability is generally low in soils, and plant responses to low P availability need to be better understood. In a previous study, we studied ...the growth and physiological responses of 24 species to low P availability in the soil and verified of eucalypts, five (
Eucalyptus acmenoides
,
E. grandis
,
E. globulus
,
E. tereticornis
, and
Corymbia maculata
) contrasted regarding their efficiency and responsiveness to soil P availability. Here, we obtained the metabolomic and lipidomic profile of leaves, stems, and roots from these species growing under low (4.5 mg dm
–3
) and sufficient (10.8 mg dm
–3
) P in the soil. Disregarding the level of P in the soils, P allocation was always higher in the stems. However, when grown in the P-sufficient soil, the stems steadily were the largest compartment of the total plant P. Under low P, the relative contents of primary metabolites, such as amino acids, TCA cycle intermediates, organic acids and carbohydrates, changed differently depending on the species. Additionally, phosphorylated metabolites showed enhanced turnover or reductions. While photosynthetic efficiencies were not related to higher biomass production,
A
/
C
i curves showed that reduced P availability increased the eucalypt species’
Vcmax, Jmax
and
photosynthetic P-use efficiency
. Plants of
E. acmenoides
increased galactolipids and sulfolipids in leaves more than other eucalypt species, suggesting that lipid remodelling can be a strategy to cope with the P shortage in this species. Our findings offer insights to understand genotypic efficiency among eucalypt species to accommodate primary metabolism under low soil P availability and eventually be used as biochemical markers for breeding programs.
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