99 research outputs found
Improved resistance to root pests: final report to Grape and Wine Research & Development Corporation
No full textThere were two major aims of this project, which was jointly funded by GWRDC and CRCV2. The first aim was to identify and characterise grapevine genes involved in the plantâ s interaction
with phylloxera and/or root-knot nematode. This information could be used to design strategies for engineering novel resistance to these pests in grapevine. The second aim of the project was to develop and use systems to rapidly assess candidate genes for preventing infestation of vine roots by phylloxera and/or root-knot nematode. Progress towards both goals was achieved despite premature termination of the project after 4, instead of 7 years.Project Leader: Dr. Robyn van Heeswijck until her retirement in July, 2002, then Prof. Steve Tyerman (in an administrative capacity); Author Details: Dr Tricia Franks (using text from the original application by Dr. Robyn van Heeswijck
Rapid identification of Acremonium lolii and Acremonium coenophialum endophytes through arbitrarily primed PCR
No full textD. Liu , R. van Heeswijck, G. Latch, T. Leonforte d, M. Panaccio, C. Langford, P. Cunningham, K. Ree
Evidence for host-associated clones of grape phylloxera Daktulosphaira vitifoliae (Hemiptera : Phylloxeridae) in Australia
No full textGrape phylloxera, Daktulosphaira vitifoliae Fitch, is an important pest of grapevines (Vitis vinifera L.) (Vitaceae). Using microsatellite DNA markers it was demonstrated strong associations can exist between D. vitifoliae asexual lineages and vine host type within a vineyard. Also, in excised root bioassays, D. vitifoliae collected from three regions where different genotypic classes predominated showed host-specific differences in life table parameters of reproductive rate and intrinsic rate of increase. Lastly, comparisons of mitochondrial DNA (cytochrome oxidase I) sequences revealed that D. vitifoliae in Australia have paraphyletic origins and fall into two clades partially related to vine host usage. These findings indicate introduction of separate lineages of D. vitifoliae which have close host associations and as such, have important implications for management of this pest in Australia.A.M. Corrie, R. van Heeswijck and A.A. Hoffman
Molecular and cellular events during the interaction of phylloxera with grapevine roots
No full textImproved knowledge of phylloxera-grapevine interactions could contribute to new control strategies. Using potted vine and in vitro dual cultures, we see that root gall (nodosity) formation on Vitis vinifera is accompanied by accumulation of starch, free amino acids and amides, indicating formation of a nutrient sink. Steady state levels of a wide range of RNA transcripts remain unaltered, suggesting that if there is a molecular response to phylloxera attack, it is either transient or restricted to only a few cells. Lower reproductive rates of phylloxera on Ramsey (V.champini) correlate with a lack of starch accumulation in root galls. Feeding attempts on V. riparia and Börner result in rapid necrosis of root tissue. No feeding attempts have been observed on V. rotundifolia. Transgenic plants and ‘hairy roots’ expressing promoter-reporter gene constructs encoding, for example, GFP or GUS, are being used to examine phylloxera-root interactions in situ.R. van Heeswijck, A. Bondar, T. Franks, L. Croser, A. Kellow, K. Powellhttp://www.actahort.org/books/617/617_1.ht
In vitro systems for studying the interaction of root-knot nematode with grapevine
No full textThe original publication can be found at www.springerlink.comA simple system for in vitro dual culture of grapevine (Vitis spp.) plantlets and root-knot nematode (Meloidogyne javanica (Treub) Chitwood) is described. Based on the presence or absence of mature females, or the total number of nematodes in the roots after 36-day co-culture, the system reliably discriminated resistant (cv. Ramsey) and susceptible (cv. Chardonnay) grapevines. The system was sensitive enough to differentiate between infestation levels of cvs Borner and Chardonnay, both susceptible in the in vitro conditions. A modification of the system to use plantlets from rooted petioles has reduced labour and space requirements and would suit mass screening of grapevine genotypes in traditional or genetic engineering-based breeding programmes. In both systems, nematodes in roots of cv. Ramsey tended to be associated with brown tissue and, compared with those in roots of cv. Chardonnay, were more likely to be con. ned to tips rather than be distributed along the root after co-culture for 11 or 36 days.Tricia K. Franks, Sandra Savocchia and Robyn Van Heeswijc
Identification of host genes involved in the biotrophic interaction between grapevine and powdery mildew
No full textGrapevine powdery mildew is caused by Erysiphe necator, an Ascomycete fungus and an obligate biotroph restricted to growth on its grapevine host. Biotrophic pathogens form a stable association with host cells without directly causing cell death, and take up nutrients from, in the case of powdery mildew ( PM ), host epidermal cells ( Rumbolz et al., 2000 ). As the fungus grows, its increasing biomass becomes a strong nutrient sink capable of altering assimilate flow and storage in the host. To identify host genes that may mediate nutrient delivery to powdery mildew infected tissues and therefore may contribute to disease susceptibility, a candidate gene approach using degenerate and RT - PCR, and a nontargeted approach using microarray analysis was instigated. Once identified, " susceptibility genes " could be targeted for manipulation to provide alternative resistance strategies based on reduced susceptibility in the future. In addition to genes encoding pathogenesis and stress related proteins, microarray analysis revealed that transcript levels of a putative metal transporter and a cell wall structural protein were elevated in infected berry skin, while aquaporin water channels and genes associated with photosynthesis were generally repressed. Degenerate PCR was used to isolated new cell wall invertase, monosaccharide and amino acid transporter genes and initial RT - PCR revealed that expression of genes involved in sugar mobilisation were the most significantly modulated by powdery mildew infection. Previously unreported hexose transporters ( HTs ), ( VvHT3, VvHT4 and VvHT5 ) and a cwINV ( VvcwINV ) had been isolated from cDNA prepared from powdery mildew infected grapevine leaves. Full length clones of grapevine HTs and cwINV were obtained by RACE PCR. Heterologous expression of the three new HTs in yeast confirmed that VvHT4 and VvHT5 mediated glucose uptake, while VvHT3 did not function in the yeast system. However, transient expression of a translational fusion of the VvHT3 protein with green florescence protein in onion epidermal cells indicated that it is targeted to the plasma membrane of plant cells. Quantitative RT - PCR analysis of these new genes, together with previously reported grapevine HTs and cytoplasmic and vacuolar invertases, indicated that expression of VvcwINV and VvHT5, were significantly up - regulated by PM infection, while a vacuolar invertase was strongly down - regulated by PM infection. Invertase activity assays were in agreement with these findings, showing elevated sucrolytic activity in insoluble fractions and reduced sucrolytic activity in soluble fractions. These results suggest that apoplasmic phloem unloading of sucrose in the infected leaf is elevated and that VvHT5 is induced to recover the additional hexoses from the apoplasm. Basic localisation studies indicated that VvHT5 and VvcwINV are not induced specifically in powdery mildew infected leaf regions, but are induced in a more diffuse distribution within infected leaves. To determine if induction of VvHT5 and VvcwINV is specific to PM infection or if other stimuli may also mediate these responses, leaves were inoculated with downy mildew or stressed by wounding. Transcript levels of VvHT5 and VvcwINV were elevated by wounding and downy mildew infection, suggesting that the induction of these genes may be part of a general stress response. To explore the signalling pathways that may underlie these responses, leaves were treated with the plant growth regulators ethylene, jasmonate and abscisic acid. Exogenous application of ethylene and methyl jasmonate only marginally affected the expression of the genes studied, however foliar application of abscisic acid ( ABA ) induced gene expression changes similar to those observed in response to powdery mildew infection and wounding. Promoter sequences of VvHT3, VvHT4, VvHT5 and VvcwINV were isolated and analysed for the presence of regulatory elements. Compared with the promoters of VvHTs that were not induced by pathogen infection or wounding, the VvHT5 and VvcwINV promoters contained numerous motifs associated with induction by ABA including ABRE, Myc and Myb binding elements. The path of sugar loading into the mesocarp of grape berries during ripening is still poorly understood and few molecular components associated with this process have been described. Quantitative RT - PCR was used to monitor the expression of five HTs and VvcwINV during Cabernet sauvignon and Shiraz berry development and ripening. Of the three new HTs reported here, the expression of VvHT3 is most consistent with a potential role in sugar loading, while VvHT5 is induced late in this process. VvcwINV transcript levels were high pre - ripening and also during the later stages of ripening, therefore based on this expression pattern, a role for this enzyme during ripening is not clearly evident. These results are discussed in terms of an apoplasmic step in phloem unloading in ripening grape berries. This study has provided new insights into the molecular and biochemical processes associated with the formation of carbohydrate sink metabolism in response to stress stimuli, and sugar delivery to grape berries during ripening. ABA - dependant pathways may mediate the stress - associated induction of VvcwINV and VvHT5, presumably to recruit additional carbohydrates to the affected organ to energise repair and defence responses. At this stage it is unknown if this response is beneficial to pathogen nutrition, however potentially, modification of genes associated with carbohydrate sink metabolism could provide an alternative way to engineer resistance to this pathogen.Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2006
Introduction: Building decolonial learning and teaching through connecting to our diverse pasts: a case for ukuzilanda
No full textThe authors of this special issue – Nondwe Mpuma, Martina van Heerden, Khanyiso Jonas and Robyn Tyler - are part of a cohort of early career academics in the Arts and Humanities Faculty at the University of the Western Cape. We are joined by co-author Athambile Masola from the University of Cape Town. We are all fewer than 5 years into our permanent position as a lecturer at our institution. We come from Lubaleko, Kariega, Durban, eMonti and Cape Town and we speak isiXhosa, Afrikaans, English and isiZulu. Our academic disciplineswithin Arts and Humanities include Linguistics, English Literature, Sociology, Academic Literacies and Historical Studies. The foregrounding of our academic, geographic and linguistic identity positions within the body of this introduction is intentional
Identification and characterization of a fruit-specific, thaumatin-like protein that accumulates at very high levels in conjunction with the onset of sugar accumulation and berry softening in grapes
No full textThe protein composition of the grape (Vitis vinifera cv Muscat of Alexandria) berry was examined from flowering to ripeness by gel electrophoresis. A protein with an apparent molecular mass of 24 kD, which was one of the most abundant proteins in extracts of mature berries, was purified and identified by amino acid sequence to be a thaumatin-like protein. Combined cDNA sequence analysis and electrospray mass spectrometry revealed that this protein, VVTL1 (for V. vinifera thaumatin-like protein 1), is synthesized with a transient signal peptide as seen for apoplastic preproteins. Apart from the removal of the targeting signal and the formation of eight disulfide bonds, VVTL1 undergoes no other posttranslational modification. Southern, northern, and western analyses revealed that VVTL1 is found in the berry only and is encoded by a single gene that is expressed in conjunction with the onset of sugar accumulation and softening. The exact role of VVTL1 is unknown, but the timing of its accumulation correlates with the inability of the fungal pathogen powdery mildew (Uncinula necator) to initiate new infections of the berry. Western analysis revealed that the presence of thaumatin-like proteins in ripening fruit might be a widespread phenomenon
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