BackgroundDowny mildew is a destructive grapevine disease caused by Plasmopara viticola (Berk. and Curt.) Berl. and de Toni, which can only be controlled by intensive fungicide treatments. Natural sources of resistance from wild grapevine (Vitis) species are used in conventional breeding approaches, but the signals and effectors involved in resistance in this important crop species are not well understood.ResultsEarly transcriptional changes associated with P. viticola infection in susceptible V. vinifera and resistant V. riparia plants were analyzed using the Combimatrix microarray platform. Transcript levels were measured 12 and 24 h post-inoculation, reflecting the time points immediately preceding the onset of resistance in V. riparia, as determined by microscopic analysis. Our data indicate that resistance in V. riparia is induced after infection, and is not based on differences in basal gene expression between the two species. The strong and rapid transcriptional reprogramming involves the induction of pathogenesis-related proteins and enzymes required for the synthesis of phenylpropanoid-derived compounds, many of which are also induced, albeit to a lesser extent, in V. vinifera. More interestingly, resistance in V. riparia also involves the specific modulation of numerous transcripts encoding components of signal transduction cascades, hypersensitive reaction markers and genes involved in jasmonate biosynthesis. The limited transcriptional modulation in V. vinifera represents a weak attempted defense response rather than the activation of compatibility-specific pathways.ConclusionsSeveral candidate resistance genes were identified that could be exploited in future biotechnological approaches to increase disease resistance in susceptible grapevine species. Measurements of jasmonic acid and methyl jasmonate in infected leaves suggest that this hormone may also be involved in V. riparia resistance to P. viticola.
BackgroundMitogen-activated protein kinase kinase kinases (MAPKKKs; MAP3Ks) are important components of MAPK cascades, which are highly conserved signal transduction pathways in animals, yeast and plants, play important roles in plant growth and development. MAPKKKs have been investigated on their evolution and expression patterns in limited plants including Arabidopsis, rice and maize.ResultsIn this study, we performed a genome-wide survey and identified 45 MAPKKK genes in the grapevine genome. Chromosome location, phylogeny, gene structure and conserved protein motifs of MAPKKK family in grapevine have been analyzed to support the prediction of these genes. In the phylogenetic analysis, MAPKKK genes of grapevine have been classified into three subgroups as described for Arabidopsis, named MEKK, ZIK and RAF, also confirmed in grapevine by the analysis of conserved motifs and exon-intron organizations. By analyzing expression profiles of MAPKKK genes in grapevine microarray databases, we highlighted the modulation of different MAPKKKs in different organs and distinct developmental stages. Furthermore, we experimentally investigated the expression profiles of 45 grape MAPKKK genes in response to biotic (powdery mildew) and abiotic stress (drought), as well as to hormone (salicylic acid, ethylene) and hydrogen peroxide treatments, and identified several candidate MAPKKK genes that might play an important role in biotic and abiotic responses in grapevine, for further functional characterization.ConclusionsThis is the first comprehensive experimental survey of the grapevine MAPKKK gene family, which provides insights into their potential roles in regulating responses to biotic and abiotic stresses, and the evolutionary expansion of MAPKKKs is associated with the diverse requirement in transducing external and internal signals into intracellular actions in MAPK cascade in grapevine.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0219-1) contains supplementary material, which is available to authorized users.
The Arabidopsis Tóxicos en Levadura (ATL) protein family is a class of E3 ubiquitin ligases with a characteristic RING-H2 Zn-finger structure that mediates diverse physiological processes and stress responses in plants. We carried out a genome-wide survey of grapevine (Vitis vinifera L.) ATL genes and retrieved 96 sequences containing the canonical ATL RING-H2 domain. We analysed their genomic organisation, gene structure and evolution, protein domains and phylogenetic relationships. Clustering revealed several clades, as already reported in Arabidopsis thaliana and rice (Oryza sativa), with an expanded subgroup of grapevine-specific genes. Most of the grapevine ATL genes lacked introns and were scattered among the 19 chromosomes, with a high level of duplication retention. Expression profiling revealed that some ATL genes are expressed specifically during early or late development and may participate in the juvenile to mature plant transition, whereas others may play a role in pathogen and/or abiotic stress responses, making them key candidates for further functional analysis. Our data offer the first genome-wide overview and annotation of the grapevine ATL family, and provide a basis for investigating the roles of specific family members in grapevine physiology and stress responses, as well as potential biotechnological applications.
Background and Aims:Mitogen-activated protein kinases have been found to play essential roles in mediating biotic and abiotic stress responses in plants. Investigation of their possible involvement in grapevine resistance to biotic or abiotic stresses and of their development will be possible only through future functional genomics experiments of gain/loss of function in the grapevine. Methods and Results: We identified and re-annotated all 12 mitogen-activated protein kinases genes from the 12X V1 sequenced grapevine genome and re-nominated them according to international standards as VvMPK. All were validated by cloning their cDNA sequences through polymerase chain reaction amplification. Expression analysis of VvMPK genes using microarray analysis and quantitative real-time polymerase chain reaction demonstrated that all VvMPK genes are expressed during grapevine growth and development. Based on expression analysis of grapevine tissues and organs at several developmental stages, and of leaf tissues treated with Erysiphe necator (powdery mildew), salicylic acid, ethylene, hydrogen peroxide and drought, we identified for further functional characterisation several VvMPK candidate genes which might be involved in grapevine growth and development and in biotic and abiotic responses. Conclusions: We identified several grapevine MPK genes modulated at the transcriptional level in several stages of grapevine growth and development and during the response to development and environmental stresses. Significance of the Study: This is the first comprehensive experimental survey of the grapevine MPK gene family, which provides insights into their potential roles in regulating responses to biotic and abiotic stresses. Ongoing functional characterisation of important candidate VvMPK genes will assist unravelling their biological roles in grapevine.
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