Identification of Quantitative Trait Loci Affecting Hemicellulose Characteristics Based on Cell Wall Composition in a Wild and Cultivated Rice Species

Cell wall hemicellulosic polysaccharides are structurally complex and diverse. Knowledge about the synthesis of cell wall hemicelluloses and their biological roles is limited. Quantitative trait loci （QTL） mapping is a helpful tool for the dissection of complex phenotypes for gene identification. In this study, we exploited the natural variation in cell wall monosaccharide levels between a common wild rice, Yuanj, and an elite indica cultivar, Teqing, and performed QTL map- ping with their introgression lines （ILs）. Chemical analyses conducted on the culms of Yuanj and TeqJng showed that the major alterations are found in glucose and xylose levels, which are correlated with specific hemicellulosic polymers. Gly- cosidic linkage examination revealed that, in Yuanj, an increase in glucose content results from a higher level of mixed linkage I^-glucan （MLG）, whereas a reduction in xylose content reflects a low level of xylan backbone and a varied arabi- noxylan （AX） structure. Seventeen QTLs for monosaccharides have been identified through composition analysis of the culm residues of 95 core ILs. Four major QTLs affecting xylose and glucose levels are responsible for 19 and 21% of the phenotypic variance, respectively. This study provides a unique resource for the genetic dissection of rice cell wall forma- tion and remodeling in the vegetative organs.

Wood forming tissue-specific expression of PdSuSy and HCHL increases holocellulose content and improves saccharification in Populus

Development of strategies to deconstruct lignocellulosic biomass in tree species is essential for biofuels and biomaterials production.We applied a wood forming tissue-specific system in a hybrid poplar to express both PdSuSy(a sucrose synthase gene from Populus deltoides×P.euramericana that has not been functionally characterized)and HCHL(the hydroxycinnamoyl-CoA hydratase-lyase gene from Pseudomonas fluorescens,which inhibits lignin polymerization in Arabidopsis).The PdSuSy-HCHL overexpression poplars correspondingly driven by the promoters of Arabidopsis AtCesA7 and AtC4 H resulted in a significant increase in cellulose(>8%),xylan(>12%)and glucose(>29%)content,accompanying a reduction in galacturonic acid(>36%)content,compared to control plants.The saccharification efficiency of these overexpression poplars was dramatically increased by up to 27%,but total lignin content was unaffected.These transgenic poplars showed inhibited growth characteristics,including>16%reduced plant height,>10% reduced number of internodes,and>18% reduced fresh weight after growth of 4 months,possibly due to relatively low expression of HCHL in secondary xylem.Our results demonstrate the structural complexity and interaction of the cell wall polymers in wood tissue and outline a potential method to increase biomass saccharification in woody species.

Assessment of fodder quality of leaves of multipurpose trees in subtropical humid climate of India

The leaves of 12 species （Acacia auriculiformis, Albizzia procera, Dalbergia sissoo, Gliricidia maculata, Leucaena leuco- cephala, Samanea saman, Azadirachta indica, Eucalyptus hybrida, Gmelina arborea, Michelia champaca, Morus alba, and Tectona grandis） of Multipurpose trees and shrubs （MPTs） grown in the agroforestry arboretum were evaluated for their nutritional characteristics in terms of proximate composition, cell wall constituents, total tannins, major （Ca and P） and trace minerals （Fe, Cu, Zn, Mn and Co）, in vitro dry matter and organic matter digestibility （IVDMD and IVOMD） and metabolisable energy （ME） values. There were significant （P〈0.01） variations among MPTs for all parameters studied. The average values of （92.02±0.30）%, （16.00±0.74）%, （3.05±0.13）%, （18.97±1.07）%, （54.00±1.12）% and （7.98 ± 0.30）% （DM basis） were observed for OM （organic matter）, CP （crude protein）, EE （ether extract）, CF （crude fibre）, NFE （nitrogen-free extract） and total ash, respectively. Leguminous trees had high CP compared to nonleguminous ones （18.30% vs 13.70%）. The mean values for cell wall constituents viz., NDF （neutral detergent fibre）, ADF （acid detergent fibre）, hemi cellulose, cellulose and ADL （acid detergent lignin） were found to be （52.48±1.05）%, （31.72±0.97）%, （20.76±0.88）%, （16.97±0.70）% and （9.57±0.62）%, respectively. The total tannin contents averaged （4.22±0.32）%. The ratio of Ca to P was quite wider. The levels of Fe and Mn were adequate to rich in all the MPTs while many of the tree species possessed P, Cu, Zn and Co level below the critical limits for the animals. The average IVDMD and IVOMD values were found to be （48.96±1.30）% and （50.69±1.36）%, respectively. The ME value averaged （6.95i-0.11） MJ·kg-1 DM. The CP content had significant positive correlation with IVDMD, IVOMD and ME val- ues while NDF, ADF, ADL and total tannins showed negative correlations with these three parameters. Based on the results, Leucaena Leucocephala could be considered as good quality fodder as it had the highest level of IVDMD/IVOMD （65.20%/67.66%） and ME （7.95 MJ·kg-1 DM） while G. maculata, M. alba, A. indica, D. sissoo and S. saman were of medium type and rest of poor quality.

Effect of Chitin Treatment on Softening of Actinidia arguta

[Objectives] This study was conducted to discuss the effect of chitin treatment on softening of Actinidia arguta Huanyou No. 1 as the test material.[Methods]Huanyou No. 1 was sprayed with chitin,and the changes of some physiological and biochemical indexes in fruit softening were investigated. [Results]Chitin treatment significantly improved single fruit weight,increased soluble solid content,but decreased titratable acid content and significantly reduced the content of cellulose and hemicellulose; and the chitin treatment significantly inhibited the breakdown of pectin,cellulose and hemicellulose,and inhibited the activities of PG enzyme and β-Gal enzyme. [Conclusions] Chitin spray treatment could increase the yield of A. arguta,and improve its quality and storage property.

Microstructure and Properties of Cement Foams Prepared by Magnesium Oxychloride Cement

Microstructural features including pore size distribution, cell walls and phase compositions of magnesium oxychloride cement foams（MOCF） with various MgO powders and water mixture ratios were studied. Their infl uences on compressive strength, water absorption and resistance of MOCF were also discussed in detail. The experimental results indicated that moderate and slight excess MgO powders（MgO/MgCl2 molar ratios from 5.1 to 7） were beneficial to the formation of excellent microstructure of MOCF, but increasing water contents（H2O/MgO mass ratios from 0.9 to 1.29） might result in opposite conclusions. The microstructure of MOCF produced with moderate and slight excess MgO powders could enhance the compressive strength, while serious excess MgO powders addition（MgO/MgCl2 molar ratios = 9） would destroy the cell wall structures, and therefore decrease the strength of the system. Although MOCF produced with excess MgO powders could decrease the water absorption, its softening coefficient was lower than that of the material produced with moderate MgO powders. This might be due to the instability of phase 5, the volume expansion and cracking of cell walls as immersed the sample into water.

Distribution,structure and biosynthetic gene families of(1,3;1,4)-β-glucan in Sorghum bicolor

In cereals, the presence of soluble polysaccharides including（1,3;1,4）-b-glucan has downstream implications for human health, animal feed and biofuel applications. Sorghum bicolor（L.） Moench is a versatile crop, but there are limited reports regarding the content of such soluble polysaccharides.Here, the amount of（1,3;1,4）-b-glucan present in sorghum tissues was measured using a Megazyme assay. Very low amounts were present in the grain, ranging from 0.16%–0.27%（w/w）, while there was a greater quantity in vegetative tissues at 0.12–1.71%（w/w）. The fine structure of（1,3;1,4）-b-glucan, as denoted by the ratio of cellotriosyl and cellotetraosyl residues,was assessed by high performance liquid chromatography（HPLC） and ranged from 2.6–3：1 in the grain, while ratios in vegetative tissues were lower at 2.1–2.6：1. The distribution of（1,3;1,4）-b-glucan was examined using a specific antibody and observed with fl uorescence and transmission electron microscopy. Micrographs showed a variable distribution of（1,3;1,4）-b-glucan in fl uenced by temporal and spatial factors. The sorghum orthologs of genes implicated in the synthesis of（1,3;1,4）-b-glucan in other cereals, such as the Cellulose synthase-like（Csl） F and H gene families were de fined.Transcript pro filing of these genes across sorghum tissues was carried out using real-time quantitative polymerase chain reaction, indicating that, as in other cereals, Csl F6 transcripts dominated.