Thaumatin-like proteins are differentially expressed and localized in phloem tissues of hybrid poplar

<p>Abstract</p> <p>Background</p> <p>Two thaumatin-like proteins (TLPs) were previously identified in phloem exudate of hybrid poplar (<it>Populus trichocarpa </it>× <it>P. deltoides) </it>using proteomics methods, and their sieve element localization confirmed by immunofluorescence. In the current study, we analyzed different tissues to further understand TLP expression and localization in poplar, and used immunogold labelling to determine intracellular localization.</p> <p>Results</p> <p>Immunofluorescence using a TLP antiserum confirmed the presence of TLP in punctate, organelle-like structures within sieve elements. On western blots, the antiserum labeled two constitutively expressed proteins with distinct expression patterns. Immunogold labelling suggested that TLPs are associated with starch granules and starch-containing plastids in sieve elements and phloem parenchyma cells. In addition, the antiserum recognized TLPs in the inner cell wall and sieve plate region of sieve elements.</p> <p>Conclusions</p> <p>TLP localization in poplar cells and tissues is complex. TLP1 is expressed predominantly in tissues with a prominent vascular system such as midveins, petioles and stems, whereas the second TLP is primarily expressed in starch-storing plastids found in young leaves and the shoot apex.</p

Expression of an expansin carbohydrate-binding module affects xylem and phloem formation

Expansins are believed to be involved in disrupting the non-covalent adhesion of cellulose to matrix polysaccharides, thereby promoting wall creep. We have targeted a putative potato expansin (EXPA) carbohydrate-binding module (CBM) to the cell walls of tobacco plants. Histological examinations and electron microscopy indicated that 30% of the xylem cells of the transgenic stems with high expression of the expansin CBM are wider (radial surface area) than those of the controls. Similarly, 37% of the xylem cells of the stems of the high expressers have thinner cell walls than those of the controls. There were no such phenotypes in the low and none expressers, as well as in the control plants. The transgenic tobacco plants expressing the potato expansin CBM did not exhibit marked change in plant morphology. Analysis of cellulose content in the stem cell walls was similar between the high expresser of the transgene and the control plants. Nonetheless, our results taken together demonstrate that expansin CBM alone can bring about changes in the plant cell walls

Neural Network for Papaya Leaf Disease Detection

The scientific name of papaya is Carica papaya which is an herbaceous perennial in the family Caricaceae grown for its edible fruit. The papaya plant is tree-like,usually unbranched and has hollow stems and petioles. Its origin is Costa Rica, Mexico and USA. The common names of papaya is pawpaw and tree melon. In East Indies and Southern Asia, it is known as tapaya, kepaya, lapaya and kapaya. In Brazil,it is known as Mamao. Papayas are a soft, fleshy fruit that can be used in a wide variety of culinary ways. The possible health benefits of consuming papaya include a reduced risk of heart disease, diabetes, cancer, aiding in digestion, improving blood glucose control in people with diabetes, lowering blood pressure, and improving wound healing. Disease identification in early stage can increase crop productivity and hence lead to economical growth. This work deals with leaf rather than fruit. Images of papaya leaf samples, image compression and image filtering and several image generation techniques are used to obtain several trained data image sets and then hence providing a better product. This paper focus on the power of neural network for detecting diseases in the papaya. Image segmentation is done with the help of k-medoid clustering algorithm which is a partitioning based clustering method

Over-expression of a chimeric gene of the transcriptional co-activator MBF1 fused to the EAR repressor motif causes developmental alteration in Arabidopsis and tomato

Transcriptional co-activators of the Multiprotein Bridging Factor1 (MBF1) type belong to a multigenic family that encode key components of the machinery controlling gene expression by communicating between transcription factors and the basal transcription machinery. Knocking-down the expression of one member of the family has proved difficult probably due to functional redundancy. We show here that a fusion of SlER24, an MBF1 type gene of tomato, to the Ethylene-responsive element-binding associated Amphiphilic Repression (EAR) motif is capable of slowing down significantly the expression of the GFP protein driven by a synthetic ethylene-responsive GCC-rich promoter in a single cell transient expression system. A fusion of AtMBF1c of Arabidopsis to EAR, driven by the 35S promoter, caused a reduction of the percentage of seed germination and dwarfism of the plant. Similar fusion with the SlER24 of tomato in the MicroTom cultivar induced a delay of seed germination and no obvious effect on plant growth. Besides giving information on the role of the MBF1 genes in plant development, this study demonstrates that the EAR strategy is efficient not only for regular transcription factors as demonstrated so far, but also in the case of co-activators known to not bind directly to DNA

Investigating the initial signalling mechanisms underpinning gene-for-gene mediated Systemic Acquired Resistance in Arabidopsis thaliana

National Overseas Scholarship Scheme to study abroad.Plants deploy two key active defensive strategies to combat microbial pathogens; (i) Recognition of Pathogen-Associated Molecular Patterns (PAMPs) by extracellular surface receptors leading to the activation of PAMP-Triggered Immunity (PTI); (ii) Recognition of pathogen effector activity, usually intracellularly, by host Resistance (R) proteins leading to Effector-Triggered Immunity (ETI). ETI is characterised by a rapid localised Hypersensitive Response (HR). HR induces Systemic Acquired Resistance (SAR) through the production of an inducible immune signal(s), leading to broad spectrum systemic resistance. I investigated the earliest events associated with SAR signalling using plant electrophysiology, SAR mutants and a unique promoter-luciferase fusion that captures early systemic transcriptional events associated with ETI. We describe the transcriptional dynamics of A70 (At5g56980), a gene of unknown function (Truman et al. 2007), in local and systemic tissue following challenge with different elicitors and virulent or avirulent pathogen challenges. We provide evidence that A70 responds to a jasmonate (JA) related signal that is rapidly generated following ETI recognition. We further evaluate A70::LUC reporter activity in response to JA stimulus and correlate activity with histological expression of a JA repressor reporter (JAZ10::GUS) and A70::GFP reporter in systemically responding leaves following avirulent pathogen challenges. Finally, we examine changes in electrophysiological signals following ETI in local and systemic leaves. Focussing on events underpinning initiation, propagation and perception of SAR-inducing signals within the first 6-8 h of pathogen challenge we provide new insight into the integrated signalling mechanisms, dynamics and connectivity underpinning systemic immune responses. We conclude that there are multicomponent signals that link ETI induced transcriptional and electrical signals, with a COI1 receptor dependent propagative transcriptional wave the leads to rapid temporal spatial activation of jasmonate responsive genes in systemic responding leaves.Ministry of Social Justice and Empowerment, Indi

Plant feeding by Nesidiocoris tenuis: Quantifying its behavioral and mechanical components

Zoophytophagous predators play an important, though sometimes controversial, role in pest management programs in different crops. In tomato crops, damage caused by phytophagy of the mirid Nesidiocoris tenuis has mainly been reported at high predator population levels or when prey is scarce. Previous research has focused on predator/prey ratios, stylet morphology and saliva composition to explain plant damage by N. tenuis. In this study, we investigated the behavioral and mechanical components of the damage. For this, we compared the feeding behaviors of males, females and fifth-instar nymphs of N. tenuis. Additionally, we investigated the type of stylet activities performed by each stage while probing in plant tissue, using the electrical penetration graph technique (EPG). Furthermore, stylectomy was performed and plant histology studied with the aim to correlate the feeding activities observed in the EPG recordings with stylet tip positions in specific tissues of the leaf petioles. Behavioral observations during a 30-min period showed that nymphs probed more frequently (38.6 ± 1.5 probes) than males and females (25.3 ± 1.1 and 24.3 ± 1.1 probes, respectively). Similarly, nymphs spent a higher proportion of time (656.0 ± 67.6 s) feeding on tomato apical sections compared to males and females (403.0 ± 48.8 s and 356.0 ± 43.7 s, respectively). The EPG recordings during 5 h indicated that cell-rupturing was the main stylet activity for all insect stages, and that fifth-instar nymphs spent a higher proportion of time on cell-rupturing events compared to adults. The histological studies revealed a trend of N. tenuis for the tissues within the vascular semi-ring. The stylet tips were found both in the vascular bundles and in the parenchyma of the interfascicular region. The findings of this study confirm an important role of fifth-instar nymphs feeding behavior in the damage potential of N. tenuis. Moreover, the increased time spent on cell rupturing behaviour suggests that stylet laceration and enzymatic maceration of the saliva occurring during this event might greatly contribute to the inflicted damage. A comprehensive understanding of the interactions of N. tenuis with the plant, at both the behavioral and mechanical levels, might shed light on new approaches to minimize its damage potential to tomato while maintaining its benefits as biocontrol agent

A three-dimensional RNA motif mediates directional trafficking of Potato spindle tuber viroid from epidermal to palisade mesophyll cells in Nicotiana benthamiana

Potato spindle tuber viroid (PSTVd) is a circular non-coding RNA of 359 nucleotides that replicates and spreads systemically in host plants, thus all functions required to establish an infection are mediated by sequence and structural elements in the genome. The PSTVd secondary structure contains 26 Watson-Crick base-paired stems and 27 loops. Most of the loops are believed to form three-dimensional (3D) structural motifs through non-Watson-Crick base pairing, base stacking, and other local interactions. Homology-based prediction using the JAR3D online program revealed that loop 27 (nucleotides 177-182) most likely forms a 3D structure similar to the loop of a conserved hairpin located in the 3\u27 untranslated region of histone mRNAs in animal cells. This stem-loop, which is involved in 3\u27-end maturation, is not found in polyadenylated plant histone mRNAs. Mutagenesis showed that PSTVd genomes containing base substitutions in loop 27 predicted by JAR3D to disrupt the 3D structure were unable to replicate in Nicotiana benthamiana leaves following mechanical rub inoculation, with one exception: a U178G/U179G double mutant was replication-competent and able to spread within the upper epidermis of inoculated leaves, but was confined to this cell layer. Remarkably, direct delivery of the U178G/U179G mutant into the vascular system by needle puncture inoculation allowed it to spread systemically and enter mesophyll cells and epidermal cells of upper leaves. These findings highlight the importance of RNA 3D structure for PSTVd replication and intercellular trafficking and indicate that loop 27 is required for epidermal exit, but not epidermal entry or transit between other cell types. Thus, requirements for RNA trafficking between epidermal and underlying palisade mesophyll cells are unique and directional. Our findings further suggest that 3D structure and RNA-protein interactions constrain RNA sequence evolution, and validate JAR3D as a tool to predict RNA 3D structure

Cloning, characterisation and expression analysis of cDNA clones encoding cell wall-modifying enzymes isolated from ripe apples

Fruit softening is accompanied by modifications of the cell wall pectic and hemicellulosic fractions, as the result of the combined action of several cell wall-modifying enzymes. The objective of this work was to clone specific cDNAs that encode isoforms of cell wall-modifying enzymes, which are expressed during the final stages of apple softening, and to establish a temporal sequence of their accumulation. A cDNA library enriched with mRNA isolated from over-ripe fruit was constructed and screened. A pectin methylesterase (MdPME1), a pectate lyase (MdPL1), an -l-arabinofuranosidase (MdAF1) an endo-1,4- -glucanase (MdEG1), two xyloglucan endotransglucosylase/hydrolases (Md-XTH1 and Md-XTH2), and an alpha-expansin (MdEXPA3) specific cDNAs were identified by homology-based cloning, and their mRNA accumulation was examined during fruit growth and ripening. The expression of an apple -galactosidase ( -Gal; pABG1) and a polygalacturonase (PG; pGDPG-1) mRNA previously reported was also investigated using the same biological material. Transcripts of all enzymes, except MdPME1, could be unambiguously detected by semi-quantitative RT-PCR in fruit during ripening. However, transcripts of MdEG1 were more abundant at fruit set and MdPL1 exhibited higher expression before commercial maturity. The strongest RT-PCR signals in over-ripe fruit were observed for PG, -Gal and Md-XTH1 clones. Two XTHs were detected in over-ripe fruit. While Md-XTH1 acts constitutively during fruit development, Md-XTH2 showed a ripening-related pattern. The Md-XTH2-encoded protein was heterologously expressed in Saccharomyces cerevisiae and showed both transglycosylase and hydrolase activities. Expression analyses conducted in flowers, peduncles, young and expanded leaves, and petioles of senescent leaves revealed that none of the cloned cDNAs is fruit specifi