Center for Plant Science Innovation

Lincoln, NE, United States

Center for Plant Science Innovation

Lincoln, NE, United States
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Guo Y.,Southwest University | Busta L.,University of British Columbia | Busta L.,Center for Plant Science Innovation | Jetter R.,University of British Columbia
Plant Physiology and Biochemistry | Year: 2017

Primary plant surfaces are coated with hydrophobic cuticular waxes to minimize non-stomatal water loss. Wax compositions differ greatly between plant species and, in the few species studied systematically so far, also between organs, tissues, and developmental stages. However, the wax mixtures of more species in diverse plant families must be investigated to assess overall wax variability, and ultimately to correlate organ-specific composition with local water barrier properties. Here, we present comprehensive analyses of the waxes covering five organs of Taraxacum officinale (dandelion), to help close a gap in our understanding of wax chemistry in the Asteraceae family. First, novel wax constituents of the petal wax were identified as C25 6,8- and 8,10-ketols as well as C27 6,8- and 8,10-ketols. Nine other component classes (fatty acids, primary alcohols, esters, aldehydes, alkanes, triterpenols, triterpene acetates, sterols, and tocopherols) were detected in the wax mixtures covering leaves, peduncles, and petals, as well as fruit beaks and pappi. Wax coverages varied from 5 μg/cm2 on peduncles to 37 μg/cm2 on petals. Alcohols predominated in leaf wax, while both alcohols and alkanes were found in similar amounts on peduncles and petals, and mainly alkanes on the fruit beaks and pappi. Chain length distributions within the wax compound classes were similar between organs, centered around C26 for fatty acids, alcohols, and aldehydes, and C29 for alkanes. However, the quantities of homologs with longer chain lengths varied substantially between organs, reaching well beyond C30 on all surfaces except leaves, suggesting differences in elongation enzymes determining the alkyl chain structures. The detailed wax profiles presented here will serve as basis for future investigations into wax biosynthesis in the Asteraceae and into wax functions on different dandelion organs. © 2017 Elsevier Masson SAS

Busta L.,University of British Columbia | Busta L.,Center for Plant Science Innovation | Jetter R.,University of British Columbia
Plant and Cell Physiology | Year: 2017

The cuticle is a waxy composite that protects the aerial organs of land plans from non-stomatal water loss. The chemical make-up of the cuticular wax mixture plays a central role in defining the water barrier, but structure-function relationships have not been established so far, in part due to gaps in our understanding of wax structures and biosynthesis. While wax compounds with saturated, linear hydrocarbon tails have been investigated in detail, very little is known about compounds with modified aliphatic tails, which comprise substantial portions of some plant wax mixtures. This study aimed to investigate the structures, abundances and biosynthesis of branched compounds on the species for which wax biosynthesis is best understood: Arabidopsis thaliana. Microscale derivatization, mass spectral interpretation and organic synthesis identified homologous series of iso-alkanes and iso-alcohols on flowers and leaves, respectively. These comprised approximately 10-15% of wild type wax mixtures. The abundances of both branched wax constituents and accompanying unbranched compounds were reduced on the cer6, cer3 and cer1 mutants but not cer4, indicating that branched compounds are in part synthesized by the same machinery as unbranched compounds. In contrast, the abundances of unbranched, but not branched, wax constituents were reduced on the cer2 and cer26 mutants, suggesting that the pathways to both types of compounds deviate in later steps of chain elongation. Finally, the abundances of branched, but not unbranched, wax compounds were reduced on the cer16 mutant, and the (uncharacterized) CER16 protein may therefore be controlling the relative abundances of iso-alkanes and iso-alcohols on Arabidopsis surfaces. © The Author 2017. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved.

News Article | January 27, 2016

While most bacteria are harmless, some inject weapons called type III effectors into plant cells to suppress a plant's immune system. Through millions of years of co-evolution, pathogens identify weak links in the immune system of the plant to target, making the plant more susceptible to disease. "If we can better understand and improve plants' immune systems, we can help increase disease resistance and improve crop quality and yields," said Alfano, a Charles Bessey Professor of Plant Pathology. The study focuses on the bacterial pathogen Pseudomonas syringae. This pathogen uses a specialized protein secretion system called the type III system, which is essentially a microsyringe, to inject bacterial type III effector proteins into plant cells. Alfano and the team have been studying different type III effectors injected into plant cells and have been identifying which parts of the immune system they are targeting. The researchers found that when HopE1 is injected into a cell, it interacts with the host plant's calmodulin calcium sensor. This sensor is normally activated during a plant's immune response to rising calcium levels in plant cells. However, the research team found that the sensor also drives HopE1 to bind with a plant protein called microtubule-associated protein 65, or MAP65. The interaction with MAP65 is significant because MAP65 plays an important role in the plant microtubule network, which is known to be involved in cell division and cell growth in higher organisms. Alfano's research group found that when HopE1 binds to MAP65, it separates the protein from the microtubule network. This chain of events results in a defective immune system, suggesting that the microtubule network is linked to immunity. When pathogens inject effectors such as HopE1 into plant cells, it prevents the plant from secreting immunity-related products and ultimately leads to plant diseases. HopE1 is just one of many effectors the research team is studying in hope of identifying new components of plant immunity, which could lead to improved disease resistance in agricultural crops. In addition to Alfano, the study was authored by Ming Guo and Guangyon Li of the Center for Plant Science Innovation and the Department of Plant Pathology; Panya Kim of the Center for Plant Science Innovation and the School of Biological Sciences; and Christian Elowsky of the Center for Biotechnology. It was published in the journal Cell Host and Microbe. Explore further: Researchers learn how pathogen causes speck disease

Qi Y.,University of Minnesota | Tsuda K.,University of Minnesota | Joe A.,Center for Plant Science Innovation | Joe A.,University of Nebraska - Lincoln | And 7 more authors.
Molecular Plant-Microbe Interactions | Year: 2010

RNA-binding proteins (RBP) can control gene expression at both transcriptional and post-transcriptional levels. Plants respond to pathogen infection with rapid reprogramming of gene expression. However, little is known about how plant RBP function in plant immunity. Here, we describe the involvement of an RBP, Arabidopsis thaliana RNA-binding protein-defense related 1 (AtRBP-DR1; At4g03110), in resistance to the pathogen Pseudomonas syringae pv. tomato DC3000. AtRBP-DR1 loss-of-function mutants showed enhanced susceptibility to P. syringae pv. tomato DC3000. Overexpression of AtRBP-DR1 led to enhanced resistance to P. syringae pv. tomato DC3000 strains and dwarfism. The hypersensitive response triggered by P. syringae pv. tomato DC3000 avrRpt2 was compromised in the Atrbp-dr1 mutant and enhanced in the AtRBP-DR1 overexpression line at early time points. AtRBP-DR1 overexpression lines showed higher mRNA levels of SID2 and PR1, which are salicylic acid (SA) inducible, as well as spontaneous cell death in mature leaves. Consistent with these observations, the SA level was low in the Atrbp-dr1 mutant but high in the overexpression line. The SA-related phenotype in the overexpression line was fully dependent on SID2. Thus, AtRBPDR1 is a positive regulator of SA-mediated immunity, possibly acting on SA signaling-related genes at a post-transcriptional level. © 2010 The American Phytopathological Society.

Xu Y.-Z.,Center for Plant Science Innovation | de la Rosa Santamaria R.,Center for Plant Science Innovation | de la Rosa Santamaria R.,University of Nebraska - Lincoln | de la Rosa Santamaria R.,Colegio de Mexico | And 13 more authors.
Plant Physiology | Year: 2012

Multicellular eukaryotes demonstrate nongenetic, heritable phenotypic versatility in their adaptation to environmental changes. This inclusive inheritance is composed of interacting epigenetic, maternal, and environmental factors. Yet-unidentified maternal effects can have a pronounced influence on plant phenotypic adaptation to changing environmental conditions. To explore the control of phenotypy in higher plants, we examined the effect of a single plant nuclear gene on the expression and transmission of phenotypic variability in Arabidopsis (Arabidopsis thaliana). MutS HOMOLOG1 (MSH1) is a plant-specific nuclear gene product that functions in both mitochondria and plastids to maintain genome stability. RNA interference suppression of the gene elicits strikingly similar programmed changes in plant growth pattern in six different plant species, changes subsequently heritable independent of the RNA interference transgene. The altered phenotypes reflect multiple pathways that are known to participate in adaptation, including altered phytohormone effects for dwarfed growth and reduced internode elongation, enhanced branching, reduced stomatal density, altered leaf morphology, delayed flowering, and extended juvenility, with conversion to perennial growth pattern in short days. Some of these effects are partially reversed with the application of gibberellic acid. Genetic hemicomplementation experiments show that this phenotypic plasticity derives from changes in chloroplast state. Our results suggest that suppression of MSH1, which occurs under several forms of abiotic stress, triggers a plastidial response process that involves nongenetic inheritance. © 2012 American Society of Plant Biologists.

Ding Y.,Anhui University of Science and Technology | Ding Y.,University of Nebraska - Lincoln | Ndamukong I.,University of Nebraska - Lincoln | Ndamukong I.,East Carolina University | And 6 more authors.
PLoS Genetics | Year: 2012

Tri-methylated H3 lysine 4 (H3K4me3) is associated with transcriptionally active genes, but its function in the transcription process is still unclear. Point mutations in the catalytic domain of ATX1 (ARABIDOPSIS TRITHORAX1), a H3K4 methyltransferase, and RNAi knockdowns of subunits of the AtCOMPASS-like (Arabidopsis Complex Proteins Associated with Set) were used to address this question. We demonstrate that both ATX1 and AtCOMPASS-like are required for high level accumulation of TBP (TATA-binding protein) and Pol II at promoters and that this requirement is independent of the catalytic histone modifying activity. However, the catalytic function is critically required for transcription as H3K4me3 levels determine the efficiency of transcription elongation. The roles of H3K4me3, ATX1, and AtCOMPASS-like may be of a general relevance for transcription of Trithorax-activated eukaryotic genes. © 2012 Ding et al.

PubMed | Howard Hughes Medical Institute, Urbana University and Center for Plant Science Innovation
Type: Journal Article | Journal: Plant, cell & environment | Year: 2016

Stable transformation of plants is a powerful tool for hypothesis testing. A rapid and reliable evaluation method of the transgenic allele for copy number and homozygosity is vital in analysing these transformations. Here the suitability of Southern blot analysis, thermal asymmetric interlaced (TAIL-)PCR, quantitative (q)PCR and digital droplet (dd)PCR to estimate T-DNA copy number, locus complexity and homozygosity were compared in transgenic tobacco. Southern blot analysis and ddPCR on three generations of transgenic offspring with contrasting zygosity and copy number were entirely consistent, whereas TAIL-PCR often underestimated copy number. qPCR deviated considerably from the Southern blot results and had lower precision and higher variability than ddPCR. Comparison of segregation analyses and ddPCR of T1 progeny from 26 T0 plants showed that at least 19% of the lines carried multiple T-DNA insertions per locus, which can lead to unstable transgene expression. Segregation analyses failed to detect these multiple copies, presumably because of their close linkage. This shows the importance of routine T-DNA copy number estimation. Based on our results, ddPCR is the most suitable method, because it is as reliable as Southern blot analysis yet much faster. A protocol for this application of ddPCR to large plant genomes is provided.

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