The 5＇ fragment （1 647 bp） of the cotton glucuronosyltransferase gene （GhGlcAT1） was transcriptionally fused to the β-glucuronidase （GUS） gene, and functionally analyzed for important regulatory regions contro...The 5＇ fragment （1 647 bp） of the cotton glucuronosyltransferase gene （GhGlcAT1） was transcriptionally fused to the β-glucuronidase （GUS） gene, and functionally analyzed for important regulatory regions controlling gene expression in transgenic tobacco plants. GUS activity analysis revealed that the full-length promoter drives efficient expression of the GUS gene in the root cap, seed coat, pollen grains and trichomes. Exposure of the transgenic tobacco to various abiotic stresses showed that the promoter was mainly responsive to the sugars （glucose and sucrose） as well as gibberellic acid. Progressive upstream deletion analyses of the promoter showed that the region from -281 to ＋30 bp is sufficient to drive strong GUS expression in the trichomes of shoot, suggesting that the 311 bp region contains all cis-elements needed for trichome-specific expression. Furthermore, deletion analysis also revealed that the essential cis-element（s） for sucrose induction might be located between -635 and -281 bp. In addition, sequence analysis of the regulatory region indicated several conserved motifs among which some were shared with previously reported seed-specific elements and sugarresponsive elements, while others were related with trichome expression. These findings indicate that a 1 647-bp fragment of the cotton GhGIcAT1 promoter contains specific transcription regulatory elements, and provide clues about the roles of GhGIcAT 1 in cotton fiber development. Further analyses of these elements will help to elucidate the molecular mechanisms regulating the expression of the GhGlcAT1 gene during fiber elongation.展开更多
A series of mesoporous Ta and Ta-W oxides have been prepared and employed as solid acid catalysts for the dehydration of fructose and glucose to 5-hydroxymethylfurfural(HMF).Solid state 31 P MAS NMR spectroscopic resu...A series of mesoporous Ta and Ta-W oxides have been prepared and employed as solid acid catalysts for the dehydration of fructose and glucose to 5-hydroxymethylfurfural(HMF).Solid state 31 P MAS NMR spectroscopic results using trimethylphosphine(TMP)as a probe molecule show that the acid strength and the ratio of Br?nsted to Lewis acid sites increase gradually with the addition of tungsten in tantalum oxide.It is found that high sugar conversion and HMF selectivity are achieved over catalyst with relatively high ratios of Br?nsted to Lewis acid sites.Unexpected stoichiometric excess of formic acid relative to levulinic acid can be observed mainly because of direct decomposition of fructose over Lewis acid sites.The addition of 2-butanol leads to the increase of sugars conversion and the HMF selectivity,especially for the catalyst with high ratio of Br?nsted to Lewis acid sites.Among them,Ta7W3 oxide catalyst shows 54%HMF selectivity and good reusability with the addition of 2-butanol by extracting HMF from aqueous phase and removing humins deposed on the surface of the catalyst.展开更多
Uridine diphosphate-glucose dehydrogenase （UGD, EC1.1.1 glucuronate）, a critical precursor of cell wall polysaccharides 22 oxidizes UDP-Glc （UDP-D-glucose） to UDP-GlcA （UDP-D- GbUGD6 from Gossypium barbadense is ...Uridine diphosphate-glucose dehydrogenase （UGD, EC1.1.1 glucuronate）, a critical precursor of cell wall polysaccharides 22 oxidizes UDP-Glc （UDP-D-glucose） to UDP-GlcA （UDP-D- GbUGD6 from Gossypium barbadense is more highly expressed late in the elongation of cotton fibers （15 d post-anthesis （DPA）） and during the stage of secondary cell wall thickening （30 DPA）. Subcellular localization analysis in onion epidermis revealed that fluorescently labeled GbUGD6 protein was distribut- ed throughout the cell membrane, as well as the nucleus and vacuoles. Examination of UGD function in Arabidopsis revealed that the antisense GbUGD6 lines had shorter roots, deferred blossoming, compared to wild-type plants. Activities of associated enzymes were also affected by UGD reduction, and biochemical analysis of cell wall samples showed an increase in cellulose levels and a decrease in UGP-GlcA contents. The results of the present study as well as previous studies on UGD support the conclusion that UGD plays a major role in synthesizing polysaccharides synthesis in the cell wall.展开更多
文摘The 5＇ fragment （1 647 bp） of the cotton glucuronosyltransferase gene （GhGlcAT1） was transcriptionally fused to the β-glucuronidase （GUS） gene, and functionally analyzed for important regulatory regions controlling gene expression in transgenic tobacco plants. GUS activity analysis revealed that the full-length promoter drives efficient expression of the GUS gene in the root cap, seed coat, pollen grains and trichomes. Exposure of the transgenic tobacco to various abiotic stresses showed that the promoter was mainly responsive to the sugars （glucose and sucrose） as well as gibberellic acid. Progressive upstream deletion analyses of the promoter showed that the region from -281 to ＋30 bp is sufficient to drive strong GUS expression in the trichomes of shoot, suggesting that the 311 bp region contains all cis-elements needed for trichome-specific expression. Furthermore, deletion analysis also revealed that the essential cis-element（s） for sucrose induction might be located between -635 and -281 bp. In addition, sequence analysis of the regulatory region indicated several conserved motifs among which some were shared with previously reported seed-specific elements and sugarresponsive elements, while others were related with trichome expression. These findings indicate that a 1 647-bp fragment of the cotton GhGIcAT1 promoter contains specific transcription regulatory elements, and provide clues about the roles of GhGIcAT 1 in cotton fiber development. Further analyses of these elements will help to elucidate the molecular mechanisms regulating the expression of the GhGlcAT1 gene during fiber elongation.
文摘A series of mesoporous Ta and Ta-W oxides have been prepared and employed as solid acid catalysts for the dehydration of fructose and glucose to 5-hydroxymethylfurfural(HMF).Solid state 31 P MAS NMR spectroscopic results using trimethylphosphine(TMP)as a probe molecule show that the acid strength and the ratio of Br?nsted to Lewis acid sites increase gradually with the addition of tungsten in tantalum oxide.It is found that high sugar conversion and HMF selectivity are achieved over catalyst with relatively high ratios of Br?nsted to Lewis acid sites.Unexpected stoichiometric excess of formic acid relative to levulinic acid can be observed mainly because of direct decomposition of fructose over Lewis acid sites.The addition of 2-butanol leads to the increase of sugars conversion and the HMF selectivity,especially for the catalyst with high ratio of Br?nsted to Lewis acid sites.Among them,Ta7W3 oxide catalyst shows 54%HMF selectivity and good reusability with the addition of 2-butanol by extracting HMF from aqueous phase and removing humins deposed on the surface of the catalyst.
基金the Ministry of Agriculture of China (2014ZX08009-003)the Hebei Province Technology Support Program (14962905D)the Hebei Province Department of Education Fund (Y2012025)
文摘Uridine diphosphate-glucose dehydrogenase （UGD, EC1.1.1 glucuronate）, a critical precursor of cell wall polysaccharides 22 oxidizes UDP-Glc （UDP-D-glucose） to UDP-GlcA （UDP-D- GbUGD6 from Gossypium barbadense is more highly expressed late in the elongation of cotton fibers （15 d post-anthesis （DPA）） and during the stage of secondary cell wall thickening （30 DPA）. Subcellular localization analysis in onion epidermis revealed that fluorescently labeled GbUGD6 protein was distribut- ed throughout the cell membrane, as well as the nucleus and vacuoles. Examination of UGD function in Arabidopsis revealed that the antisense GbUGD6 lines had shorter roots, deferred blossoming, compared to wild-type plants. Activities of associated enzymes were also affected by UGD reduction, and biochemical analysis of cell wall samples showed an increase in cellulose levels and a decrease in UGP-GlcA contents. The results of the present study as well as previous studies on UGD support the conclusion that UGD plays a major role in synthesizing polysaccharides synthesis in the cell wall.
