Exploiting Genetic Variation of Fiber Components and Morphology in Juvenile Loblolly Pine.

In order to ensure the global competitiveness of the Pulp and Paper Industry in the Southeastern U.S., more wood with targeted characteristics have to be produced more efficiently on less land. The objective of the research project is to provide a molecular genetic basis for tree breeding of desirable traits in juvenile loblolly pine, using a multidisciplinary research approach. We developed micro analytical methods for determine the cellulose and lignin content, average fiber length, and coarseness of a single ring in a 12 mm increment core. These methods allow rapid determination of these traits in micro scale. Genetic variation and genotype by environment interaction (GxE) were studied in several juvenile wood traits of loblolly pine (Pinus taeda L.). Over 1000 wood samples of 12 mm increment cores were collected from 14 full-sib families generated by a 6-parent half-diallel mating design (11-year-old) in four progeny tests. Juvenile (ring 3) and transition (ring 8) for each increment core were analyzed for cellulose and lignin content, average fiber length, and coarseness. Transition wood had higher cellulose content, longer fiber and higher coarseness, but lower lignin than juvenile wood. General combining ability variance for the traits in juvenile wood explained 3 to 10% of the total variance, whereas the specific combining ability variance was negligible or zero. There were noticeable full-sib family rank changes between sites for all the traits. This was reflected in very high specific combining ability by site interaction variances, which explained from 5% (fiber length) to 37% (lignin) of the total variance. Weak individual-tree heritabilities were found for cellulose, lignin content and fiber length at the juvenile and transition wood, except for lignin at the transition wood (0.23). Coarseness had moderately high individual-tree heritabilities at both the juvenile (0.39) and transition wood (0.30). Favorable genetic correlations of volume and stem straightness were found with cellulose content, fiber length and coarseness, suggesting that selection on growth or stem straightness would results in favorable response in chemical wood traits. We have developed a series of methods for application of functional genomics to understanding the molecular basis of traits important to tree breeding for improved chemical and physical properties of wood. Two types of technologies were used, microarray analysis of gene expression, and profiling of soluble metabolites from wood forming tissues. We were able to correlate wood property phenotypes with expression of specific genes and with the abundance of specific metabolites using a new database and appropriate statistical tools. These results implicate a series of candidate genes for cellulose content, lignin content, hemicellulose content and specific extractible metabolites. Future work should integrate such studies in mapping populations and genetic maps to make more precise associations of traits with gene locations in order to increase the predictive power of molecular markers, and to distinguish between different candidate genes associated by linkage or by function. This study has found that loblolly pine families differed significantly for cellulose yield, fiber length, fiber coarseness, and less for lignin content. The implication for forest industry is that genetic testing and selection for these traits is possible and practical. With sufficient genetic variation, we could improve cellulose yield, fiber length, fiber coarseness, and reduce lignin content in Loblolly pine. With the continued progress in molecular research, some candidate genes may be used for selecting cellulose content, lignin content, hemicellulose content and specific extractible metabolites. This would accelerate current breeding and testing program significantly, and produce pine plantations with not only high productivity, but desirable wood properties as well

Honeycomb Films of Cellulose Azide: Molecular Structure and Formation of Porous Films

Development of value-added micropatterned porous materials from naturally abundant polymers, such as cellulose, are of growing interest. In this paper, regioselectively modified amphiphilic cellulose azide, 3-<i>O</i>-azidopropoxypoly­(ethylene glycol)-2,6-di-<i>O</i>-thexyldimethylsilyl cellulose, with different degrees of substitution (DS) and degrees of polymerization (DP) of the poly­(ethylene glycol) (PEG) side chain, was synthesized and employed in the formation of honeycomb-patterned films. With the variation of the DP and/or DS, the amphiphilicity of the polymer and the pore size of the formed films changed accordingly. It was found that amphiphilicity of the cellulose azide played a significant role in the formation of honeycomb films. Balanced amphiphilicity was of particular importance in the formation of uniform honeycomb films. Via the Cu^I-catalyzed alkyne–azide [2 + 3] cycloaddition reaction, fluorescent avidin and quantum dots were attached to the films. By means of confocal microscopy, it was confirmed that the functional azido group was preferentially allocated inside the pores. This provides a platform for the development of advanced honeycomb materials with site-specific functionalities, such as biosensors

Preparation and Characterization of Kraft Lignin-Based Moisture-Responsive Films with Reversible Shape-Change Capability

Preparation of moisture-responsive Kraft lignin-based materials by electrospinning blends of Kraft lignin fractions with different physical properties is presented. The differences in thermal mobility between lignin fractions are shown to influence the degree of interfiber fusion occurring during oxidative thermostabilization of electrospun nonwoven fabrics, resulting in different material morphologies including submicrometer fibers, bonded nonwovens, porous films, and smooth films. The relative amount of different lignin fractions and degree of fiber flow and fiber fusion is shown to influence the tendency for the electrospun materials to be transformed into moisture-responsive materials capable of reversible changes in shape. Material characterization by scanning electron microscopy and atomic force microscopy as well characterization of the chemical and physical properties of Kraft lignin fractions by dynamic rheology, ¹H and ¹³C NMR, and gel permeation chromatography combined with multiangle laser light scattering are presented. A proposed mechanism underlying moisture-responsiveness, shape change, and shape recovery is discussed based on the differences in chemical structure and physical properties of Kraft lignin fractions

Design of Functionalized Cellulosic Honeycomb Films: Site-Specific Biomolecule Modification via “Click Chemistry”

Value-added materials from naturally abundant polymers such as cellulose are of significant importance. In particular, cellulosic open-framework structures with controlled chemical functionality of the internal surface have great potential in many biosensor applications. Although various cellulose derivatives can form porous honeycomb structured materials, solubility issues and problems with film formation exist. To address this, we have generated robust cellulosic open-framework structures that can be post-functionalized through site-specific modification. Regioselectively modified amphiphilic cellulose azides, 3-<i>O</i>-azidopropoxypoly­(ethylene glycol)-2,6-di-<i>O</i>-thexyldimethylsilyl cellulosics, were synthesized, and honeycomb-patterned films were readily produced by the simple breath figures method. Changing the degree of polymerization (DP) of the pendent ethylene glycol (EG_DP) groups from 22 to 4 increased the corresponding honeycomb film pore diameters from ∼1.2 to ∼2.6 μm, enabling the potential tuning of pore size. Moreover, these novel azido-functionalized honeycomb films were easily functionalized using Cu­(I)-catalyzed alkyne–azide [2 + 3] cycloaddition reaction; biotin was “clicked” onto the azide functionalized cellulosic honeycomb films without any effect to the film structure. These results indicate this system may serve as a platform for the design and development of biosensors