Plant growth-defense tradeoffs are fundamental for optimizing plant performance and fitness in a changing biotic/abiotic environment. This process is thought to involve readjusting resource allocation to different pathways. It has been frequently observed that among secondary cell wall components, alteration in lignin biosynthesis results in changes in both growth and defense. How this process is regulated, leading to growth or defense, remains largely elusive. In this article, we review the canonical lignin biosynthesis pathway, the recently discovered tyrosine shortcut pathway, and the biosynthesis of unconventional C-lignin. We summarize the current model of the hierarchical transcriptional regulation of lignin biosynthesis. Moreover, the interface between recently identified transcription factors and the hierarchical model are also discussed. We propose the existence of a transcriptional co-regulation mechanism coordinating energy allowance among growth, defense and lignin biosynthesis.

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Careful preoperative selection of patients in terms of the Child-Pugh classification and decrease of intraoperative blood loss are important measures to reduce postoperative morbidity after major hepatic resection in HCC patients with underlying liver diseases. Moreover, we should be aware that preoperative platelet count is independently associated with postoperative morbidity and mortality for those patients following major hepatic resection.

The AML1 gene, located on chromosome 21, is involved in several distinct chromosomal translocations in human leukemia. In t(8;21) acute myelogenous leukemia (AML), the AML1 gene is juxtaposed to the ETO gene located on chromosome 8, generating an AML1͞ETO fusion protein. Both AML1͞ETO and the AML1 proteins recognize the same consensus DNA-binding motif (TGT͞CGGT), which is found in the promoters of several genes involved in hematopoiesis. We found that two myeloid leukemia cell lines with the t(8;21) translocation, Kasumi and SKNO-1, have elevated levels of BCL-2 protein compared with other myeloid cell lines. In addition, we identified a consensus AML1 binding site in the BCL-2 promoter. Thus far, AML1͞ETO has been shown to dominantly repress its target genes; however, we found that AML1͞ETO activates transcription of the BCL-2 gene in U937 cells. This activation requires the presence of both the runt homology domain (rhd) and the C-terminal portion of AML1͞ ETO. We demonstrated sequence specific binding of both AML1A and AML1͞ETO to the TGTGGT sequence in the BCL-2 promoter and showed that the AML1 binding site is required for responsiveness to AML1͞ETO. Interestingly, AML1A and AML1B do not modulate the activity of the BCL-2 promoter. The elevated levels of BCL-2 in cells that express AML1͞ETO may prolong their life span and contribute to the development of t(8;21) leukemia.Chromosomal translocations found in human leukemia frequently involve genes that code for transcription factors (1). In acute myeloid leukemia (AML) with the t(8;21) chromosomal translocation, which occurs in Ϸ40% cases of AML with the M2 French-American-British subtype, coding sequences of the AML1 gene (on chromosome 21) are juxtaposed to coding sequences of the ETO gene (on chromosome 8) generating an AML1͞ETO fusion protein (2, 3). The AML1 family of transcription factors recognize the binding sequence 5Ј-TGT͞ CGGT-3Ј (2) through an 117-amino acid region that is highly homologous to the Drosophila segmentation gene runt (2, 3), and has been called the runt homology domain (rhd). This domain is necessary for DNA binding, as well as for proteinprotein interactions (3). At least three forms of AML1 protein are produced by alternative splicing (4). The AML1-B isoform (479 amino acids) contains the rhd and a putative C-terminal transcriptional activation domain; the AML1-A isoform (250 amino acids) contains the DNA binding domain, but lacks the potential transcriptional activation domain. AML1-B, but not A ML-1A, can transactivate the human granulocyte͞ macrophage colony-stimulating factor (GM-CSF) promoter (5) and the T cell receptor ␤ enhancer (6), whereas both isoforms can transactivate the human interleukin 3 (IL-3) gene (H.U., S.Z., and S.D.N., unpublished work).The genes encoding AML1 or its dimerization partner CBF␤, have been shown to be involved in several other translocations in human acute leukemia (7). The AML1 gene is fused to the TEL gene in t(12;21) acute lymphoblastic leukemia (8). In the t(3;21) translocation, seen ...

BackgroundWUSCHEL (WUS)-related homeobox (WOX) protein family members play important roles in the maintenance and proliferation of the stem cell niche in the shoot apical meristem (SAM), root apical meristem (RAM), and cambium (CAM). Although the roles of some WOXs in meristematic cell regulation have been well studied in annual plants such as Arabidopsis and rice, the expression and function of WOX members in woody plant poplars has not been systematically investigated. Here, we present the identification and comprehensive analysis of the expression and function of WOXs in Populus tomentosa.ResultsA genome-wide survey identified 18 WOX encoding sequences in the sequenced genome of Populus trichocarpa (PtrWOXs). Phylogenetic and gene structure analysis revealed that these 18 PtrWOXs fall into modern/WUS, intermediate, and ancient clades, but that the WOX genes in P. trichocarpa may have expanded differently from the WOX genes in Arabidopsis. In the P. trichocarpa genome, no WOX members could be closely classified as AtWOX3, AtWOX6, AtWOX7, AtWOX10, and AtWOX14, but there were two copies of WOX genes that could be classified as PtrWUS, PtrWOX2, PtrWOX4, PtrWOX5, PtrWOX8/9, and PtrWOX11/12, and three copies of WOX genes that could be classified as PtrWOX1 and PtrWOX13. The use of primers specific for each PtrWOX gene allowed the identification and cloning of 18 WOX genes from P. tomentosa (PtoWOXs), a poplar species physiologically close to P. trichocarpa. It was found that PtoWOXs and PtrWOXs shared very high amino acid sequence identity, and that PtoWOXs could be classified identically to PtrWOXs. We revealed that the expression patterns of some PtoWOXs were different to their Arabidopsis counterparts. When PtoWOX5a and PtoWOX11/12a, as well as PtoWUSa and PtoWOX4a were ectopically expressed in transgenic hybrid poplars, the regeneration of adventitious root (AR) was promoted, indicating a functional similarity of these four WOXs in AR regeneration.ConclusionsThis is the first attempt towards a systematical analysis of the function of WOXs in P. tomentosa. A diversified expression, yet functional similarity of PtoWOXs in AR regeneration is revealed. Our findings provide useful information for further elucidation of the functions and mechanisms of WOXs in the development of poplars.

To isolate transcription factors important in the regulation of the human interleukin-3 (IL-3) gene, we screened a gt11 cDNA library, constructed from phytohemagglutinin-stimulated human T-cell RNA, with a probe containing regulatory sequences in the upstream region of the IL-3 gene (located from bp ؊165 to ؊128 and referred to as the DNase I footprint A region). We isolated a 0.96-kb cDNA that encoded a basic amino acid domain and a leucine zipper domain and used the ''rapid amplification and cloning of 3 ends'' technique to isolate the 3 half of the cDNA clone, generating a 1.9-kb full-length cDNA clone. Using in vitro-translated protein, which we call NF-IL3A, we defined the IL-3 promoter sequences bound by NF-IL3A in DNase I footprinting assays as TAATTACGTCTG and, using gel shift assays, defined ATTACG as the minimal sequence Interleukin-3 (IL-3) is a multilineage hematopoietic growth factor which stimulates the proliferation of hematopoietic progenitor cells and enhances the functional activity of mature effector cells (27,36). The expression of IL-3 is restricted to activated, but not resting, T cells, natural killer (NK) cells, and mast cell lines (9,27,29). In order to examine the regulatory mechanisms controlling the expression of IL-3, several investigators, including ourselves, have identified regulatory elements in the 5Ј-flanking region of the IL-3 promoter (3,10,13,19,21,22,33,35). These regulatory elements include a consensus AP-1 binding site, which can bind c-Fos/c-Jun heterodimers (13), several consensus binding sites for ets proteins (13), a CD28 response element (12, 35), and two regions identified by DNase I footprinting experiments as the A region and the B region (35). The A region contains regulatory sequences important in the inducible expression of 33,35), and methylation interference experiments have identified several distinct regions within this A region that are involved in DNAprotein interactions (10, 37). Electrophoretic mobility shift assays (EMSAs) combined with UV cross-linking have identified several proteins of 56 to 65 kDa that are capable of binding to the IL-3 A region (37).To identify and characterize IL-3 A region-binding proteins, we screened a phytohemagglutinin (PHA)-stimulated human T-cell cDNA gt11 expression library with a 32 P-labeled, multimerized, double-stranded IL-3 A region synthetic oligonucleotide probe. Approximately one million recombinant clones were screened, and one clone that generated a ␤-galactosidase fusion product that bound to the IL-3 A region but not to unrelated control DNA was identified. DNA sequence analysis of this clone demonstrated the presence of a potential DNAbinding basic-amino-acid region and a leucine zipper repeat. The 3Ј portion of the cDNA clone was not present, so rapid amplification and cloning of 3Ј ends (3Ј RACE) was performed to generate a full-length cDNA clone.A 1.9-kb full-length cDNA that contains the entire coding region for a 58-kDa protein that we call NF-IL3A was generated. In vitro-translated NF-IL3A binds specifi...

3-O-caffeoylquinic acid, also known as chlorogenic acid (CGA), functions as an intermediate in lignin biosynthesis in the phenylpropanoid pathway. It is widely distributed among numerous plant species and acts as an antioxidant in both plants and animals. Using GC-MS, we discovered consistent and extreme variation in CGA content across a population of 739 4-yr-old Populus trichocarpa accessions. We performed genome-wide association studies (GWAS) from 917 P. trichocarpa accessions and expression-based quantitative trait loci (eQTL) analyses to identify key regulators. The GWAS and eQTL analyses resolved an overlapped interval encompassing a hydroxycinnamoyl-CoA:shikimate hydroxycinnamoyl transferase 2 (PtHCT2) that was significantly associated with CGA and partially characterized metabolite abundances. PtHCT2 leaf expression was significantly correlated with CGA abundance and it was regulated by cis-eQTLs containing W-box for WRKY binding. Among all nine PtHCT homologs, PtHCT2 is the only one that responds to infection by the fungal pathogen Sphaerulina musiva (a Populus pathogen). Validation using protoplast-based transient expression system suggests that PtHCT2 is regulated by the defense-responsive WRKY. These results are consistent with reports of CGA functioning as an antioxidant in response to biotic stress. This study provides insights into data-driven and omics-based inference of gene function in woody species.

Plant cell walls provide structural support for growth and serve as a barrier for pathogen attack. Plant cell walls are also a source of renewable biomass for conversion to biofuels and bioproducts. Understanding plant cell wall biosynthesis and its regulation is of critical importance for the genetic modification of plant feedstocks for cost-effective biofuels and bioproducts conversion and production. Great progress has been made in identifying enzymes involved in plant cell wall biosynthesis, and in Arabidopsis it is generally recognized that the regulation of genes encoding these enzymes is under a transcriptional regulatory network with coherent feedforward and feedback loops. However, less is known about the transcriptional regulation of plant secondary cell wall (SCW) biosynthesis in woody species despite of its high relevance to biofuels and bioproducts conversion and production. In this article, we synthesize recent progress on the transcriptional regulation of SCW biosynthesis in Arabidopsis and contrast to what is known in woody species. Furthermore, we evaluate progress in related emerging regulatory machineries targeting transcription factors in this complex regulatory network of SCW biosynthesis.