@article{nakatsubo_ragamustari_hattori_ono_yamamura_li_chiang_umezawa_2014, title={A new O-methyltransferase for monolignol synthesis in Carthamus tinctorius}, volume={31}, ISSN={["1342-4580"]}, DOI={10.5511/plantbiotechnology.14.0903a}, abstractNote={A novel type of O-methyltransferase (OMT) cDNA was isolated from maturing seeds of Carthamus tinctorius (safflower). The deduced sequence of the OMT protein showed moderate sequence identity (52%) with C. tinctorius 5-hydroxyconiferaldehyde O-methyltransferase 1 (CAldOMT1). Phylogenetic analysis showed that the novel OMT did not belong to the typical CAldOMT [=caffeic acid OMT (CAOMT)] cluster. The recombinant protein of the OMT catalyzed 3(or 5-) O-methylation of hydroxycinnamaldehydes and hydroxycinnamyl alcohols, while it showed only weak or moderate activity toward hydroxycinnamates and hydroxycinnamoyl coenzyme A esters. Therefore, this OMT was designated as C. tinctorius 5-hydroxyconiferaldehyde/5-hydroxyconiferyl alcohol OMT (CtAAOMT). The time profile of CtAAOMT gene expression in C. tinctorius matched the patterns of lignin accumulation. Taken together, our data strongly suggest that along with CtCAldOMT1, CtAAOMT is involved in biosynthesis of syringyl lignin.}, number={5}, journal={Plant Biotechnology}, author={Nakatsubo, Tomoyuki and Ragamustari, Safendrri Komara and Hattori, Takefumi and Ono, Eiichiro and Yamamura, Masaomi and Li, Laigeng and Chiang, Vincent L. and Umezawa, Toshiaki}, year={2014}, month={Dec}, pages={545–553} }
 @article{umezawa_ragamustari_nakatsubo_wada_li_yamamura_sakakibara_hattori_suzuki_chiang_2013, title={A lignan O-methyltransferase catalyzing the regioselective methylation of matairesinol in Carthamus tinctorius}, volume={30}, ISSN={["1342-4580"]}, DOI={10.5511/plantbiotechnology.12.1230a}, abstractNote={Lignans are a group of plant phenolic compounds with various biological activities, including antitumor and antioxidant properties. O-Methylation is a critical step in biosynthesis of these compounds. However, little is known about the O-methyltransferase (OMT) enzymes that catalyze lignan O-methylation. We discovered a highly regioselective OMT activity in safflower (Carthamus tinctorius) seeds that catalyzed the methylation of matairesinol, a dibenzylbutyrolactone lignan, into 4′-O-methylmatairesinol (arctigenin) but not 4-O-methylmatairesinol (isoarctigenin). By examining such OMT activity in correlation with OMT transcript abundances during seed development, we cloned a few putative OMT cDNAs and produced their recombinant proteins in Escherichia coli. Among them, one protein exhibited O-methylation activity for matairesinol with the regioselectivity identical to that of the plant protein, and was named C. tinctorius matairesinol OMT (CtMROMT). CtMROMT did not show any detectable OMT activities towards phenylpropanoid monomers under the reaction conditions tested, while it methylated flavonoid apigenin efficiently into 4′-O-methylapigenin (acacetin). However, quantitative real-time polymerase chain reaction analysis demonstrated that expression of the CtMROMT gene was synchronized with the CtMROMT activity profile and arctigenin accumulation in the plant. These results demonstrated that CtMROMT is a novel plant OMT for lignan methylation.}, number={2}, journal={PLANT BIOTECHNOLOGY}, author={Umezawa, Toshiaki and Ragamustari, Safendrri Komara and Nakatsubo, Tomoyuki and Wada, Shohei and Li, Laigeng and Yamamura, Masaomi and Sakakibara, Norikazu and Hattori, Takefumi and Suzuki, Shiro and Chiang, Vincent L.}, year={2013}, pages={97–109} }
 @article{suzuki_sakakibara_li_umezawa_chiang_2010, title={Profiling of phenylpropanoid monomers in developing xylem tissue of transgenic aspen (Populus tremuloides)}, volume={56}, ISSN={["1435-0211"]}, DOI={10.1007/s10086-009-1059-8}, abstractNote={Here we describe alterations in the cinnamate/monolignol pathway in three transgenic aspen lines: one with downregulated expression of 4-coumarate:CoA ligase (4CL), one with upregulated expression of coniferaldehyde 5-hydroxylase (CAld5H), and a 4CL downregulated/CAld5H upregulated line. Compared with the wild type, the 4CL downregulated line showed significantly increased levels of p-hydroxycinnamic acids such as p-coumaric, ferulic, and sinapic acids. In contrast, the CAld5H upregulated line had increased content of p-coumaryl and 5-hydroxyconiferyl alcohols. In the 4CL downregulated line, it was likely that most hydroxycinnamic acids were glycosylated. These results strongly suggest that the downregulation of 4CL and upregulation of CAld5H disrupt the metabolic flow through the cinnamate/monolignol pathway and thus alter the amount and structure of its final product, lignin.}, number={1}, journal={JOURNAL OF WOOD SCIENCE}, author={Suzuki, Shiro and Sakakibara, Norikazu and Li, Laigeng and Umezawa, Toshiaki and Chiang, Vincent L.}, year={2010}, month={Feb}, pages={71–76} }
 @article{nakatsubo_li_hattori_lu_sakakibara_chiang_shimada_suzuki_umezawa_2008, title={Roles of 5-hydroxyconiferylaldehyde and caffeoyl CoA O-methyltransferases in monolignol biosynthesis in Carthamus tinctorius}, volume={41}, number={9-10}, journal={Cellulose Chemistry and Technology}, author={Nakatsubo, T. and Li, L. and Hattori, T. and Lu, S. and Sakakibara, N. and Chiang, V. L. and Shimada, M. and Suzuki, S. and Umezawa, T.}, year={2008}, pages={511–520} }
 @article{kasal_peszlen_peralta_li_2007, title={Preliminary tests to evaluate the mechanical properties of young trees with small diameter}, volume={61}, ISSN={["0018-3830"]}, DOI={10.1515/HF.2007.054}, abstractNote={Abstract
            This paper describes methods developed to test the mechanical properties of small-diameter (3–10 mm) 1-year-old trees. Special test fixtures and procedures were designed to accommodate the small diameter and uneven shape of these young trees. The modulus of elasticity and strength in tension parallel to the grain, compression parallel to the grain, and bending were measured.}, number={4}, journal={HOLZFORSCHUNG}, author={Kasal, Bohumil and Peszlen, Ilona and Peralta, Perry and Li, Laigeng}, year={2007}, pages={390–393} }
 @misc{li_lu_chiang_2006, title={A genomic and molecular view of wood formation}, volume={25}, ISSN={["1549-7836"]}, DOI={10.1080/07352680600611519}, abstractNote={Wood formation is a process derived from plant secondary growth. Different from primary growth, plant secondary growth is derived from cambium meristem cells in the vascular and cork cambia and leads to the girth increase of the plant trunk. In the secondary growth process, plants convert most of photosynthesized products into various biopolymers for use in the formation of woody tissues. This article summarizes the new developments of genomic and genetic characterization of wood formation in herbaceous model plant and tree plant systems. Genomic studies have categorized a collection of the genes for which expression is associated with secondary growth. During wood formation, the expression of many genes is regulated in a stage-specific manner. The function of many genes involved in wood biosyntheses and xylem differentiation has been characterized. Although great progress has been achieved in the molecular and genomic understanding of plant secondary growth in recent years, the profound genetic mechanisms underlying this plant development remain to be investigated. Completion of the first tree genome sequence (Populus genome) provides a valuable genomic resource for characterization of plant secondary growth.}, number={3}, journal={CRITICAL REVIEWS IN PLANT SCIENCES}, author={Li, Laigeng and Lu, Shanfa and Chiang, Vincent}, year={2006}, pages={215–233} }
 @article{lu_zhou_li_chiang_2006, title={Distinct roles of cinnamate 4-hydroxylase genes in Populus}, volume={47}, ISSN={["1471-9053"]}, DOI={10.1093/pcp/pcj063}, abstractNote={Cinnamate 4-hydroxylase (C4H) catalyzes the conversion of cinnamate into 4-hydroxy-cinnamate, a key reaction of the phenylpropanoid pathway which leads to the biosynthesis of several secondary metabolites. C4H genes exist as a multigene family in various plant species. In order to understand the roles of individual C4H members, four C4H cDNAs (PtreC4H) were isolated from Populus tremuloides and three C4H loci (PtriC4H) were identified in the P. trichocarpa genome. The ability of Populus C4H isoforms to convert trans-cinnamate into p-coumaric acid was verified by the examination of yeast recombinant PtreC4H proteins. Populus C4H genes were expressed in various tissues, including developing xylem, phloem and epidermis; however, the expression patterns of individual members were different from each other. Sequential analysis of C4H promoters showed that the differential expression of C4H genes was associated with cis-acting regulatory elements such as box L, box P and H box, suggesting that the divergent C4H isoforms played distinct roles in the production of secondary metabolites. The involvement of specific C4H isoforms in the biosynthesis of guaiacyl and syringyl monolignols is discussed.}, number={7}, journal={PLANT AND CELL PHYSIOLOGY}, author={Lu, Shanfa and Zhou, Yihua and Li, Laigeng and Chiang, Vincent L.}, year={2006}, month={Jul}, pages={905–914} }
 @article{hancock_loya_giardina_li_chiang_pregitzer_2007, title={Plant growth, biomass partitioning and soil carbon formation in response to altered lignin biosynthesis in Populus tremuloides}, volume={173}, ISSN={["1469-8137"]}, DOI={10.1111/j.1469-8137.2006.01965.x}, abstractNote={We conducted a glasshouse mesocosm study that combined (13)C isotope techniques with wild-type and transgenic aspen (Populus tremuloides) in order to examine how altered lignin biosynthesis affects plant production and soil carbon formation. Our transgenic aspen lines expressed low stem lignin concentration but normal cellulose concentration, low lignin stem concentration with high cellulose concentration or an increased stem syringyl to guaiacyl lignin ratio. Large differences in stem lignin concentration observed across lines were not observed in leaves or fine roots. Nonetheless, low lignin lines accumulated 15-17% less root C and 33-43% less new soil C than the control line. Compared with the control line, transformed aspen expressing high syringyl lignin accumulated 30% less total plant C - a result of greatly reduced total leaf area - and 70% less new soil C. These findings suggest that altered stem lignin biosynthesis in Populus may have little effect on the chemistry of fine roots or leaves, but can still have large effects on plant growth, biomass partitioning and soil C formation.}, number={4}, journal={NEW PHYTOLOGIST}, author={Hancock, Jessica E. and Loya, Wendy M. and Giardina, Christian P. and Li, Laigeng and Chiang, Vincent L. and Pregitzer, Kurt S.}, year={2007}, pages={732–742} }
 @article{yamada_yeh_chang_li_kadla_chiang_2006, title={Rapid analysis of transgenic trees using transmittance near-infrared spectroscopy (NIR)}, volume={60}, ISSN={["1437-434X"]}, DOI={10.1515/HF.2006.005}, abstractNote={Abstract
            Genetic engineering of trees has generated a large amount of interest in the development of highly improved transgenic trees. To efficiently monitor and control the properties of the transgenic products, a rapid, mini-scale analytical method is required. Transmittance near-infrared (NIR) spectroscopy was chosen as a fast analysis tool for characterizing the chemical properties of the transgenic products. Pellets were prepared from 75 mg of wood meal and directly scanned using transmittance NIR spectroscopy. Very strong correlations were obtained between the NIR data and conventional wet-chemistry results for the lignin content, S/G ratio, cellulose and xylose content. The results indicate that transmittance NIR is a powerful tool for determining and screening the chemical properties of transgenic trees.}, number={1}, journal={HOLZFORSCHUNG}, author={Yamada, T and Yeh, TF and Chang, HM and Li, LG and Kadla, JF and Chiang, VL}, year={2006}, month={Jan}, pages={24–28} }
 @article{suzuki_li_sun_chiang_2006, title={The cellulose synthase gene superfamily and biochemical functions of xylem-specific cellulose synthase-like genes in Populus trichocarpa}, volume={142}, ISSN={["1532-2548"]}, DOI={10.1104/pp.106.086678}, abstractNote={AbstractWood from forest trees modified for more cellulose or hemicelluloses could be a major feedstock for fuel ethanol. Xylan and glucomannan are the two major hemicelluloses in wood of angiosperms. However, little is known about the genes and gene products involved in the synthesis of these wood polysaccharides. Using Populus trichocarpa as a model angiosperm tree, we report here a systematic analysis in various tissues of the absolute transcript copy numbers of cellulose synthase superfamily genes, the cellulose synthase (CesA) and the hemicellulose-related cellulose synthase-like (Csl) genes. Candidate Csl genes were characterized for biochemical functions in Drosophila Schneider 2 (S2) cells. Of the 48 identified members, 37 were found expressed in various tissues. Seven CesA genes are xylem specific, suggesting gene networks for the synthesis of wood cellulose. Four Csl genes are xylem specific, three of which belong to the CslA subfamily. The more xylem-specific CslA subfamily is represented by three types of members: PtCslA1, PtCslA3, and PtCslA5. They share high sequence homology, but their recombinant proteins produced by the S2 cells exhibited distinct substrate specificity. PtCslA5 had no catalytic activity with the substrates for xylan or glucomannan. PtCslA1 and PtCslA3 encoded mannan synthases, but PtCslA1 further encoded a glucomannan synthase for the synthesis of (1→4)-β-d-glucomannan. The expression of PtCslA1 is most highly xylem specific, suggesting a key role for it in the synthesis of wood glucomannan. The results may help guide further studies to learn about the regulation of cellulose and hemicellulose synthesis in wood.}, number={3}, journal={PLANT PHYSIOLOGY}, author={Suzuki, Shiro and Li, Laigeng and Sun, Ying-Hsuan and Chiang, Vincent L.}, year={2006}, month={Nov}, pages={1233–1245} }
 @article{li_cheng_lu_nakatsubo_umezawa_chiang_2005, title={Clarification of cinnamoyl co-enzyme a reductase catalysis in monolignol biosynthesis of aspen}, volume={46}, ISSN={["1471-9053"]}, DOI={10.1093/pcp/pci120}, abstractNote={Cinnamoyl co-enzyme A reductase (CCR), one of the key enzymes involved in the biosynthesis of monolignols, has been thought to catalyze the conversion of several cinnamoyl-CoA esters to their respective cinnamaldehydes. However, it is unclear which cinnamoyl-CoA ester is metabolized for monolignol biosynthesis. A xylem-specific CCR cDNA was cloned from aspen (Populus tremuloides) developing xylem tissue. The recombinant CCR protein was produced through an Escherichia coli expression system and purified to electrophoretic homogeneity. The biochemical properties of CCR were characterized through direct structural corroboration and quantitative analysis of the reaction products using a liquid chromatography-mass spectrometry system. The enzyme kinetics demonstrated that CCR selectively catalyzed the reduction of feruloyl-CoA from a mixture of five cinnamoyl CoA esters. Furthermore, feruloyl-CoA showed a strong competitive inhibition of the CCR catalysis of other cinnamoyl CoA esters. Importantly, when CCR was coupled with caffeoyl-CoA O-methyltransferase (CCoAOMT) to catalyze the substrate caffeoyl-CoA ester, coniferaldehyde was formed, suggesting that CCoAOMT and CCR are neighboring enzymes. However, the in vitro results also revealed that the reactions mediated by these two neighboring enzymes require different pH environments, indicating that compartmentalization is probably needed for CCR and CCoAOMT to function properly in vivo. Eight CCR homologous genes were identified in the P. trichocarpa genome and their expression profiling suggests that they may function differentially.}, number={7}, journal={PLANT AND CELL PHYSIOLOGY}, author={Li, LG and Cheng, XF and Lu, SF and Nakatsubo, T and Umezawa, T and Chiang, VL}, year={2005}, month={Jul}, pages={1073–1082} }
 @misc{chiang_li_2005, title={Methods for simultaneous control of lignin content and composition, and cellulose content in plants}, volume={6855864}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Chiang, V. L. C. and Li, L.}, year={2005} }
 @article{lu_sun_shi_clark_li_chiang_2005, title={Novel and mechanical stress-responsive microRNAs in Populus trichocarpa that are absent from Arabidopsis}, volume={17}, DOI={10.1105/tpc.105.033456}, abstractNote={Abstract
               MicroRNAs (miRNAs) are small, noncoding RNAs that can play crucial regulatory roles in eukaryotes by targeting mRNAs for silencing. To test whether miRNAs play roles in the regulation of wood development in tree species, we isolated small RNAs from the developing xylem of Populus trichocarpa stems and cloned 22 miRNAs. They are the founding members of 21 miRNA gene families for 48 miRNA sequences, represented by 98 loci in the Populus genome. A majority of these miRNAs were predicted to target developmental- and stress/defense-related genes and possible functions associated with the biosynthesis of cell wall metabolites. Of the 21 P. trichocarpa miRNA families, 11 have sequence conservation in Arabidopsis thaliana but exhibited species-specific developmental expression patterns, suggesting that even conserved miRNAs may have different regulatory roles in different species. Most unexpectedly, the remaining 10 miRNAs, for which 17 predicted targets were experimentally validated in vivo, are absent from the Arabidopsis genome, suggesting possible roles in tree-specific processes. In fact, the expression of a majority of the cloned miRNAs was upregulated or downregulated in woody stems in a manner consistent with tree-specific corrective growth against tension and compression stresses, two constant mechanical loads in trees. Our results show that plant miRNAs can be induced by mechanical stress and may function in one of the most critical defense systems for structural and mechanical fitness.}, number={8}, journal={Plant Cell}, author={Lu, S. F. and Sun, Y. H. and Shi, R. and Clark, C. and Li, L. G. and Chiang, V. L.}, year={2005}, pages={2186–2203} }
 @misc{chiang_li_2004, title={Genetic engineering of syringyl-enriched lignin in plants}, volume={6812377}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Chiang, V. L. C. and Li, L.}, year={2004} }
 @article{lu_shi_tsao_yi_li_chiang_2004, title={RNA silencing in plants by the expression of siRNA duplexes}, volume={32}, ISSN={["1362-4962"]}, DOI={10.1093/nar/gnh170}, abstractNote={In animal cells, stable RNA silencing can be achieved by vector-based small interfering RNA (siRNA) expression system, in which Pol III RNA gene promoters are used to drive the expression of short hairpin RNA, however, this has not been demonstrated in plants. Whether Pol III RNA gene promoter is capable of driving siRNA expression in plants is unknown. Here, we report that RNA silencing was achieved in plants through stable expression of short hairpin RNA, which was driven by Pol III RNA gene promoters. Using glucuronidase (GUS) transformed tobacco as a model system, the results demonstrated that 21 nt RNA duplexes, targeting at different sites of GUS gene, were stably expressed under the control of either human H1 or Arabidopsis 7SL RNA gene promoter, and GUS gene was silenced in 80% of siRNA transgenics. The severity of silencing was correlated with the abundance of siRNA expression but independent of the target sites and uridine residue structures in siRNA hairpin transcripts. Thus, the specific expression of siRNA provides a new system for the study of siRNA silencing pathways and functional genomics in plants. Moreover, the effectiveness of the human H1 promoter in a plant background suggested a conserved mechanism underlying Pol III complex functionality.}, number={21}, journal={NUCLEIC ACIDS RESEARCH}, author={Lu, SF and Shi, R and Tsao, CC and Yi, XP and Li, LG and Chiang, VL}, year={2004} }
 @article{li_zhou_cheng_sun_marita_ralph_chiang_2003, title={Combinatorial modification of multiple lignin traits in trees through multigene cotransformation}, volume={100}, ISSN={["0027-8424"]}, DOI={10.1073/pnas.0831166100}, abstractNote={
            Lignin quantity and reactivity [which is associated with its syringyl/guaiacyl (S/G) constituent ratio] are two major barriers to wood-pulp production. To verify our contention that these traits are regulated by distinct monolignol biosynthesis genes, encoding 4-coumarate–CoA ligase (4CL) and coniferaldehyde 5-hydroxylase (CAld5H), we used
            Agrobacterium
            to cotransfer antisense
            4CL
            and sense
            CAld5H
            genes into aspen (
            Populus tremuloides
            ). Trees expressing each one and both of the transgenes were produced with high efficiency. Lignin reduction by as much as 40% with 14% cellulose augmentation was achieved in antisense
            4CL
            plants; S/G-ratio increases as much as 3-fold were observed without lignin quantity change in sense
            CAld5H
            plants. Consistent with our contention, these effects were independent but additive, with plants expressing both transgenes having up to 52% less lignin, a 64% higher S/G ratio, and 30% more cellulose. An S/G-ratio increase also accelerated cell maturation in stem secondary xylem, pointing to a role for syringyl lignin moieties in coordinating xylem secondary wall biosynthesis. The results suggest that this multigene cotransfer system should be broadly useful for plant genetic engineering and functional genomics.
          }, number={8}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Li, L and Zhou, YH and Cheng, XF and Sun, JY and Marita, JM and Ralph, J and Chiang, VL}, year={2003}, month={Apr}, pages={4939–4944} }