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1.
J Exp Bot ; 71(1): 356-369, 2020 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-31557299

RESUMO

Maize can grow in cool temperate climates but is often exposed to spring chilling temperatures that can affect early seedling growth. Here, we used two sister double-haploid lines displaying a contrasted tolerance to chilling to identify major determinants of long-term chilling tolerance. The chilling-sensitive (CS) and the chilling-tolerant (CT) lines were grown at 14 °C day/10 °C night for 60 d. CS plants displayed a strong reduction in growth and aerial biomass compared with CT plants. Photosynthetic efficiency was affected with an increase in energy dissipation in both lines. Chilling tolerance in CT plants was associated with higher chlorophyll content, glucose-6-phosphate dehydrogenase activity, and higher sucrose to starch ratio. Few changes in cell wall composition were observed in both genotypes. There was no obvious correlation between nucleotide sugar content and cell wall polysaccharide composition. Our findings suggest that the central starch-sucrose metabolism is one major determinant of the response to low temperature, and its modulation accounts for the ability of CT plants to cope with low temperature. This modulation seemed to be linked to a strong alteration in the biosynthesis of nucleotide sugars that, at a high level, could reflect the remobilization of carbon in response to chilling.


Assuntos
Carbono/metabolismo , Temperatura Baixa , Zea mays/metabolismo , Adaptação Fisiológica/genética , Zea mays/genética
2.
Plant Physiol Biochem ; 184: 75-86, 2022 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-35636334

RESUMO

Maize (Zea mays L.) is one of the major cereal crops in the world and is highly sensitive to low temperature. Here, changes in photosynthetic and cell wall metabolisms were investigated during a long chilling exposure in inbred line F2 and a low-lignin near-isogenic brown midrib3 mutant (F2bm3), which has a mutation in the caffeic acid O-methyltransferase (COMT) gene. Results revealed that the plant biomass was reduced, and this was more pronounced in F2bm3. Photosynthesis was altered in both lines with distinct changes in photosynthetic pigment content between F2bm3 and F2, indicating an alternative photoprotection mechanism between lines under chilling. Starch remobilization was observed in F2bm3 while concentrations of sucrose, fructose and starch increased in F2, suggesting a reduced sugar partitioning in F2. The cell wall was altered upon chilling, resulting in changes in the composition of glucuronorabinoxylan and a reduced cellulose level in F2. Chilling shifted lignin subunit composition in F2bm3 mutant to a higher proportion of p-hydroxyphenyl (H) units, whereas it resulted in lignin with a higher proportion of syringyl (S) residues in F2. On average, the total cell wall ferulic acid (FA) content increased in both genotypes, with an increase in ether-linked FA in F2bm3, suggesting a greater degree of cross-linking to lignin. The reinforcement of the cell wall with lignin enriched in H-units and a higher concentration in cell-wall-bound FA observed in F2bm3 as a response to chilling, could be a strategy to protect the photosystems.


Assuntos
Lignina , Zea mays , Parede Celular/metabolismo , Lignina/metabolismo , Fotossíntese/genética , Amido/metabolismo , Zea mays/genética , Zea mays/metabolismo
3.
Carbohydr Polym ; 262: 117943, 2021 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-33838820

RESUMO

Aspergillus spp. are well-known producers of pectinases commonly used in the industry. Aspergillus aculeatinus is a recently identified species but poorly characterized. This study aimed at giving a comprehensive characterization of the enzymatic potential of the O822 strain to produce Rhamnogalacturonan type I (RGI)-degrading enzymes. Proteomic analysis identified cell wall degrading enzymes (cellulases, hemicellulases, and pectinases) that accounted for 92 % of total secreted proteins. Twelve out of fifty proteins were identified as RGI-degrading enzymes. NMR and enzymatic assays revealed high levels of arabinofuranosidase, arabinanase, galactanase, rhamnogalacturonan hydrolases and rhamnogalacturonan acetylesterase activities in aqueous extracts. Viscosity assays carried out with RGI-rich camelina mucilage confirmed the efficiency of enzymes secreted by O822 to hydrolyze RGI, by decreasing viscosity by 70 %. Apple juice trials carried out at laboratory and pilot scale showed an increase in filtration flow rate and yield, paving the way for an industrial use of enzymes derived from A. aculeatinus.


Assuntos
Aspergillus/enzimologia , Filtração/métodos , Sucos de Frutas e Vegetais , Proteínas Fúngicas/metabolismo , Ramnogalacturonanos/metabolismo , Metabolismo dos Carboidratos , Celulases/metabolismo , Manipulação de Alimentos/métodos , Glicosídeo Hidrolases/metabolismo , Hidrolases/metabolismo , Malus , Pectinas/metabolismo , Poligalacturonase/metabolismo , Proteômica
4.
Carbohydr Polym ; 248: 116752, 2020 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-32919555

RESUMO

Rhamnogalaturonans I (RGI) pectins, which are a major component of the plant primary cell wall, can be recalcitrant to digestion by commercial enzymatic cocktails, in particular during fruit juice clarification process. To overcome these problems and get better insights into RGI degradation, three RGI degrading enzymes (RHG: Endo-rhamnogalacturonase; ABF: α-Arabinofuranosidases; GAN: Endo-ß-1,4-galactanase) from Aspergillus aculeatinus were expressed in Pichia pastoris, purified and fully biochemically characterized. All three enzymes showed acidic pH optimum, and temperature optima between 40-50 °C. The Km values were 0.5 mg.ml-1, 1.64 mg.ml-1 and 3.72 mg.ml-1 for RHG, ABF, GAN, respectively. NMR analysis confirmed an endo-acting mode of action for RHG and GAN, and exo-acting mode for ABF. The application potential of these enzymes was assessed by measuring changes in viscosity of RGI-rich camelina mucilage, showing that RHG-GAN enzymes induced a decrease in viscosity by altering the structures of the RGI backbone and sidechains.


Assuntos
Aspergillus/enzimologia , Proteínas Fúngicas/metabolismo , Pectinas/metabolismo , Aspergillus/genética , Aspergillus/metabolismo , Parede Celular/química , Estabilidade Enzimática , Proteínas Fúngicas/genética , Glicosídeo Hidrolases/genética , Glicosídeo Hidrolases/metabolismo , Concentração de Íons de Hidrogênio , Cinética , Espectroscopia de Ressonância Magnética , Pichia/genética , Polissacarídeo-Liases/genética , Polissacarídeo-Liases/metabolismo , Proteínas Recombinantes/metabolismo , Temperatura
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