Chung-Jui Tsai

University of Georgia | UGA · Warnell School of Forestry and Natural Resources

Cortical microtubules (MTs) are evolutionarily conserved cytoskeletal components with specialized roles in plants, including regulation of cell wall biogenesis. MT functions and dynamics are dictated by the composition of their monomeric subunits, α- (TUA) and β-tubulins (TUB), which in animals and protists are subject to both transcriptional regul...

Cortical microtubules are integral to plant morphogenesis, cell wall synthesis, and stomatal behaviour, presumably by governing cellulose microfibril orientation. Genetic manipulation of tubulins often leads to abnormal plant development, making it difficult to probe additional roles of cortical microtubules in cell wall biogenesis. Here, it is sho...

Knockout experiments are critical for the evaluation of gene function. Researchers have increasingly relied on genome editing technologies for precise mutagenesis at loci of interest, using engineered nucleases such as Zinc finger nucleases, transcription activator-like effector nucleases (TALENs), and CRISPR (clustered regularly interspaced short...

Transgenic Populus tremula x alba (717-1B4) plants with reduced expression of a tonoplast sucrose efflux transporter, PtaSUT4, exhibit reduced shoot growth compared to wild type (WT) under sustained mild drought. The present study was undertaken to determine whether SUT4-RNAi directly or indirectly altered poplar predisposition and/or response to c...

Woody perennial trees annually transition between photoautotrophic and heterotrophic states. As carbohydrate accumulation and utilization patterns shift, so does the expression of genes encoding various sucrose-proton symporters (SUTs). The poplar genome contains five SUT gene family members involved in intracellular and long-distance sucrose trans...

In Arabidopsis (Arabidopsis thaliana), overproduction of salicylic acid (SA) increases disease resistance and abiotic stress tolerance but penalizes growth. This growth–defense trade-off has hindered the adoption of SA-based disease management strategies in agriculture. However, investigation of how SA inhibits plant growth has been challenging bec...

Non-structural carbohydrate reserves of stems and roots underpin overall tree fitness and productivity under short-rotation management practices such as coppicing for bioenergy. While sucrose and starch comprise the predominant stem carbohydrate reserves of Populus, utilization for fitness and agricultural productivity is understood primarily in te...

Non-structural carbohydrate reserves of stems and roots underpin overall tree fitness as well as productivity under short-rotation management practices such as coppicing for bioenergy. While both sucrose and starch comprise the predominant carbohydrate reserves of Populus , utilization is understood primarily in terms of starch turnover. The tonopl...

Humans have been modifying plant traits for thousands of years, first through selection (i.e., domestication) then modern breeding, and in the last 30 years, through biotechnology. These modifications have resulted in increased yield, more efficient agronomic practices, and enhanced quality traits. Precision knowledge of gene regulation and functio...

Populus species play a foundational role in diverse ecosystems and are important renewable feedstocks for bioenergy and bioproducts. Hybrid aspen Populus tremula × P. alba INRA 717-1B4 is a widely used transformation model in tree functional genomics and biotechnology research. As an outcrossing interspecific hybrid, its genome is riddled with sequ...

Plant establishment requires the formation and development of an extensive root system with architecture modulated by complex genetic networks. Here, we report the identification of the PtrXB38 gene as an expression quantitative trait loci (eQTL) hotspot, mapped using 390 leaf and 444 xylem Populus trichocarpa transcriptomes. Among predicted target...

The phytohormone salicylic acid (SA) is known to regulate plant immunity against pathogens. Plants synthesize SA via the isochorismate synthase (ICS) pathway or the phenylalanine ammonia-lyase (PAL) pathway. The ICS pathway has been fully characterized using Arabidopsis thaliana, a model plant that exhibits pathogen-inducible SA accumulation. Many...

Woody perennials including Populus spp. (poplars) have a juvenile phase that ranges from several years to decades in length. This and the year-long floral development process are major impediments to breeding and to fundamental research of reproductive traits. Here we report a CRISPR-empowered in vitro flowering system and demonstrate its applicati...

Leaf osmotic adjustment by the active accrual of compatible organic solutes (e.g., sucrose) contributes to drought tolerance throughout the plant kingdom. In Populus tremula x alba, PtaSUT4 encodes a tonoplast sucrose-proton symporter whose down-regulation by chronic mild drought or transgenic manipulation is known to increase leaf sucrose and turg...

Salicylic acid (SA) and jasmonic acid (JA) often play distinct roles in plant defence against pathogens. Research from Arabidopsis thaliana has established that SA‐ and JA‐mediated defences are more effective against biotrophs and necrotrophs, respectively. These two hormones often interact antagonistically in response to particular attackers, with...

As the focus for CRISPR-edited plants moves from proof-of-concept to real-world applications, precise gene manipulation will increasingly require concurrent multiplex editing for polygenic traits. A common approach for editing across multiple sites is to design one gRNA per target; however, this complicates construct assembly and increases the poss...

Phylloquinone (vitamin K1) is a thylakoid-embedded electron carrier essential for photosynthesis. Paradoxically, we found that phylloquinone biosynthesis is retained in the nonphotosynthetic holoparasite Phelipanche aegyptiaca (Egyptian broomrape). The phylloquinone pathway genes are preferentially expressed during development of the invasive organ...

Phylloquinone is a lipophilic naphthoquinone found predominantly in chloroplasts and best known for its function in photosystem I electron transport and disulfide bridge formation of photosystem II subunits. Phylloquinone has also been detected in plasma membrane preparations of heterotrophic tissues with potential transmembrane redox function, but...

The tonoplast sucrose transporter PtaSUT4 is well expressed in leaves of Populus tremula × Populus alba (INRA 717‐IB4), and its inhibition by RNA‐interference (RNAi) alters leaf sucrose homeostasis. Whether sucrose partitioning between the vacuole and the cytosol is modulated by PtaSUT4 for specific physiological outcomes in Populus remains unexplo...

Phylloquinone is a lipophilic naphthoquinone found predominantly in chloroplasts and best known for its function in photosystem I electron transport and disulfide bridge formation of photosystem II subunits. Phylloquinone has also been detected in plasma membrane preparations of heterotrophic tissues with potential transmembrane redox function, but...

The lignin biosynthetic pathway is highly conserved in angiosperms, yet pathway manipulations give rise to a variety of taxon-specific outcomes. Knockout of lignin-associated 4-coumarate:CoA ligases (4CLs) in herbaceous species mainly reduces guaiacyl (G) lignin and enhances cell wall saccharification. Here we show that CRISPR-knockout of 4CL1 in p...

Leaf sucrose contents are high in species of the genus Populus and other temperate tree taxa. Sucrose is subcellularly compartmentalized, but assumptions about the physiological relevance of such partitioning remain largely unexplored. In this study, the effects of partial defoliation treatments on water uptake, leaf gas exchange properties, non-st...

The lignin biosynthetic pathway is highly conserved in angiosperms, yet pathway manipulations give rise to a variety of taxon-specific outcomes. Knockout of lignin-associated 4-coumarate:CoA ligases ( 4CLs ) in herbaceous species mainly reduces guaiacyl (G) lignin and enhances cell wall saccharification. Here we show that CRISPR-knockout of 4CL1 in...

Crassulacean acid metabolism (CAM) is a carbon-concentrating mechanism that has evolved numerous times across flowering plants and is thought to be an adaptation to water limited environments. CAM has been investigated from physiological and biochemical perspectives, but little is known about how plants evolve from C3 to CAM at the genetic or metab...

Highlight Although large differences in metabolism exist between C 3 and CAM species, we find that many CAM genes have shared expression patterns regardless of photosynthetic pathway, suggesting ancestral propensity for CAM. Abstract Crassulacean acid metabolism (CAM) is a carbon-concentrating mechanism that has evolved numerous times across flowe...

Polyphagous insect herbivores possess diverse mechanisms to overcome challenges of feeding in multiple plant species including, but not limited to, transcriptional plasticity and associations with obligate or facultative symbionts. The Asian longhorned beetle (Anoplophora glabripennis) is a polyphagous wood-feeder capable of developing on over 100...

Pectins are networks of dynamically and variably modified, galacturonan-rich polymers that occur predominantly in the primary cell wall and the middle lamella between cells. Despite their low abundance in lignocellulosic feedstocks, pectins can have outsized, and often negative effects on post-harvest processing. There is compelling evidence that p...

Plant cell walls exhibit architectural and compositional changes throughout their development and in response to external cues. While tubulins are involved in cell wall biogenesis, much remains unknown about the scope of their involvement during the orchestration of this resource-demanding process. A transgenic approach coupled with cell wall compo...

Plant roots exude numerous metabolites into the soil that influence nutrient availability. Although root exudate composition is hypothesized to be under selection in low fertility soils, few studies have tested this hypothesis in a phylogenetic framework. In this study, we examined root exudates of three pairs of Helianthus species chosen as phylog...

Leaf defenses are widely recognized as key adaptations and drivers of plant evolution. Across environmentally diverse habitats, the macroevolution of leaf defenses can be predicted by the univariate trade‐off model, which predicts that defenses are functionally redundant and thus trade off, and the resource availability hypothesis, which predicts t...

The CRISPR/Cas9 technology is a welcome breakthrough for genome editing, owing to its precision, efficiency, versatility and ease of adoption. We recently reported the first application of CRISPR/Cas9 for biallelic mutations in stably transformed Populus, extending the species range of this powerful technology to woody perennials. An underappreciat...

Plant root systems mediate ecological processes in the rhizosphere through the exudation of organic compounds. Although exudate composition is thought to depend strongly on plant nutrient status, little is known about the influence of multi-nutrient stresses. In this study, we examined responses to short-term (3 d) nutrient limitation in Helianthus...

Populus species are widely distributed across the Northern Hemisphere. The genetic diversity makes the genus an ideal study system for traits of ecological or agronomic significance. However, sequence variation between the genome-sequenced Populus trichocarpa Nisqually-1 and many other Populus species and hybrids poses significant challenges for re...

Figure S1. Comparisons of bark and xylem RNA-Seq data analysis using the variant-substituted P. tremula x abla 717 (sPta717) genome or the P. trichocarpa (Ptr_v3) reference genome. (a-b) Transcript abundance in bark (a) and xylem (b). Genes with significantly different FPKM values are highlighted in red (higher in sPta717) or blue (higher in Ptr_v3...

Table S1. Tissue sources of total RNA used for cDNA-primed genome amplification. Table S2. List of NGS datasets used in this study. Table S3. Identification of 717 genomic variants. Table S4. Number of expressed genes detected using the two different genomes. Table S5. Mapping rates of DNA-Seq and ChIP-Seq reads. Table S6. Re-annotation of Affymetr...

The genetic diversity of Populus species makes the genus a rich resource for functional genomic studies and agronomic trait improvement. However, sequence variation between the reference (P. trichocarpa) genome and that of the routinely transformed genotype (P. tremula x alba 717-1B4) poses significant challenges for research. Techniques such as qu...

Sucrose transporters (SUTs) are essential for the export and efficient movement of sucrose from source leaves to sink organs in plants. The angiosperm SUT family was previously classified into three or four distinct groups, Types I, II (subgroup IIB), and III, with dicot-specific Type I and monocot-specific Type IIB functioning in phloem loading. T...

The diversity of phenylpropanoids offers a rich inventory of bioactive chemicals that can be exploited for plant improvement and human health. Recent evidence suggests that glycosylation may play a role in the partitioning of phenylpropanoid precursors for a variety of downstream uses. This work reports the functional characterization of a stress-r...

Abstract available at: http://2014.botanyconference.org/engine/search/index.php?func=detail&aid=123

4-Coumarate:CoA ligase (4CL) catalyzes the formation of hydroxycinnamoyl-CoA esters for phenylpropanoid biosynthesis. Phylogenetically distinct Class I and Class II 4CL isoforms occur in angiosperms, and support lignin and non-lignin phenylpropanoid biosynthesis, respectively. In contrast, the few experimentally characterized gymnosperm 4CLs are as...

The partitioning of carbon for growth, storage and constitutive chemical defenses is widely framed in terms of a hypothetical sink-source differential that varies with nutrient supply. According to this framework, phenolics accrual is passive and occurs in source leaves when normal sink growth is not sustainable due to a nutrient limitation. In ass...

Unlabelled: With the rapid increase of omics data, correlation analysis has become an indispensable tool for inferring meaningful associations from a large number of observations. Pearson correlation coefficient (PCC) and its variants are widely used for such purposes. However, it remains challenging to test whether an observed association is reli...

Polynucleotide constructs contain fiber-specific elements which are used to target expression of polynucleotides and polypeptides to the vascular fibers of a plant. The constructs can be contained within a vector. Transgenic plants transformed with the fiber-specific elements can be made which have expression of a polynucleotide or polypeptide dire...

Key message: Our study has identified pathways and gene candidates that may be associated with the greater flexibility and digestibility of the poplar cell walls. With the goal of facilitating lignin removal during the utilization of woody biomass as a biofuel feedstock, we previously transformed a hybrid poplar clone with a partial cDNA sequence...

Salicylic acid (SA) has long been implicated in plant responses to oxidative stress. SA overproduction in Arabidopsis thaliana leads to dwarfism, making in planta assessment of SA effects difficult in this model system. We report that transgenic Populus tremula × alba expressing a bacterial SA synthase hyperaccumulated SA and SA conjugates without...

Background: Glutamine synthetase (GS) plays a central role in plant nitrogen assimilation, a process intimately linked to soil water availability. We previously showed that hybrid poplar (Populus tremula X alba, INRA 717-1B4) expressing ectopically a pine cytosolic glutamine synthetase gene (GS1a) display enhanced tolerance to drought. Preliminary...

Whole-genome microarray analysis (Agilent Populus whole genome array; 4x44K platform) of genes differentially expressed between wild type and GS transgenics. Differential expression was determined by p-values adjusted with the SLIM method [74], with a fold-change cut-off of two. Relative expression (log ratio of GS/wild type) in four tissues [sink...

Two-way ANOVA of observed transcript levels of SOD genes (all tissues vs. water availability) in wild type plants. Genes are sorted by P-values. Genes with P-values ≤0.05 appear in bold. (DOCX)

Two-way ANOVA of observed transcript levels of SOD genes between the two genotypes across all tissues in each growth condition. Genes are sorted by P-values. Genes with P-values ≤0.05 appear in bold. (DOCX)