RESUMO
BACKGROUND: Small heat shock proteins (sHSPs) belong to the class of molecular chaperones that respond to biotic and abiotic stresses in plants. A previous study has showed strong induction of the gene GmHsp22.4 in response to the nematode Meloidogyne javanica in a resistant soybean genotype, while repression in a susceptible one. This study aimed to investigate the functional involvement of this small chaperone in response to M. javanica in Arabidopsis thaliana. First, it was evaluated the activation of the promoter region after the nematode inoculation, and the occurrence of polymorphisms between resistant and susceptible re-sequenced soybean accessions. Then functional analysis using A. thaliana lines overexpressing the soybean GmHsp22.4 gene, and knocked-out mutants were challenged with M. javanica infestation. RESULTS: High expression levels of the GFP gene marker in transformed A. thaliana plants revealed that the promoter region of GmHsp22.4 was strongly activated after nematode inoculation. Moreover, the multiplication of the nematode was significantly reduced in plants overexpressing GmHsp22.4 gene in A. thaliana compared to the wild type. Additionally, the multiplication of M. javanica in the A. thaliana mutants was significantly increased mainly in the event athsp22.0-2. This increase was not that evident in the event athsp22.0-1, the one that preserved a portion of the promoter region, including the HSEs in the region around - 83 bp. However, structural analysis at sequence level among soybean resistant and susceptible genotypes did not detect any polymorphisms in the whole gene model. CONCLUSIONS: The soybean chaperone GmHsp22.4 is involved in the defense response to root-knot nematode M. javanica in A. thaliana. Specifically, the promoter region covering until - 191 from the transcriptional start site (TSS) is necessary to promoter activation after nematode infection in Arabidopsis. No polymorphisms that could explain these differences in the defense response were detected in the GmHsp22.4 gene between resistant and susceptible soybean genotypes. Therefore, further investigation is needed to elucidate the triggering factor of the plant's defense mechanism, both at the sequence level of the soybean genotypes presenting contrasting reaction to root-knot nematode and by detecting cis-elements that are essential for the activation of the GmHsp22.4 gene promoter.
Assuntos
Resistência à Doença/genética , Genes de Plantas , Glycine max/genética , Proteínas de Choque Térmico/genética , Doenças das Plantas/genética , Tylenchoidea/imunologia , Animais , Arabidopsis/genética , Resistência à Doença/imunologia , Técnicas de Inativação de Genes , Genótipo , Proteínas de Fluorescência Verde , Proteínas de Choque Térmico/imunologia , Doenças das Plantas/imunologia , Doenças das Plantas/parasitologia , Raízes de Plantas/genética , Regiões Promotoras Genéticas , Glycine max/imunologia , Glycine max/parasitologiaRESUMO
Wild peanut relatives (Arachis spp.) are genetically diverse and were adapted to a range of environments during the evolution course, constituting an important source of allele diversity for resistance to biotic and abiotic stresses. The wild diploid A. stenosperma harbors high levels of resistance to a variety of pathogens, including the root-knot nematode (RKN) Meloidogyne arenaria, through the onset of the Hypersensitive Response (HR). In order to identify genes and regulators triggering this defense response, a comprehensive root transcriptome analysis during the first stages of this incompatible interaction was conducted using Illumina Hi-Seq. Overall, eight cDNA libraries were produced generating 28.2 GB, which were de novo assembled into 44,132 contigs and 37,882 loci. Differentially expressed genes (DEGs) were identified and clustered according to their expression profile, with the majority being downregulated at 6 DAI, which coincides with the onset of the HR. Amongst these DEGs, 27 were selected for further qRT-PCR validation allowing the identification of nematode-responsive candidate genes that are putatively related to the resistance response. Those candidates are engaged in the salycilic (NBS-LRR, lipocalins, resveratrol synthase) and jasmonic (patatin, allene oxidase cyclase) acids pathways, and also related to hormonal balance (auxin responsive protein, GH3) and cellular plasticity and signaling (tetraspanin, integrin, expansin), with some of them showing contrasting expression behavior between Arachis RKN-resistant and susceptible genotypes. As these candidate genes activate different defensive signaling systems, the genetic (HR) and the induced resistance (IR), their pyramidding in one genotype via molecular breeding or transgenic strategy might contribute to a more durable resistance, thus improving the long-term control of RKN in peanut.
Assuntos
Arachis/genética , Resistência à Doença/fisiologia , Doenças das Plantas/imunologia , Doenças das Plantas/parasitologia , Tylenchoidea/imunologia , Animais , Ciclopentanos/metabolismo , Perfilação da Expressão Gênica , Genes de Plantas , Lipocalinas/metabolismo , Oxilipinas/metabolismo , Raízes de Plantas/genética , Resveratrol , Estilbenos/metabolismoRESUMO
This study aimed to evaluated the resistance and susceptibility of 10 cowpea cultivars to Meloidogyne incognita in field studies and to analyze the kinetics of the enzymes superoxide dismutase, catalase, peroxidase, chitinase, ß-1,3-glucanases and cystein proteinase inhibitors in the root system of two contrasting cowpea cultivars after inoculation with M. incognita. The cultivars CE-31 and Frade Preto were highly resistant; CE-28, CE-01, CE-315, CE-237, were very resistant; CE-70 and CE-216 were moderately resistant, whereas Vita-3 and CE-109 were slightly resistant. In the roots of the highly resistant cultivar CE-31 the activity of the antioxidant enzyme superoxide dismutase increased and catalase decreased and those of the pathogenesis-related proteins chitinase, ß-1,3-glucanase, peroxidase and cystein proteinase inhibitor increased in comparison with the root system of the slightly resistant CE-109, during the course of M. incognita infestation. Thus the changes in the activities of these enzymes might be related to the smaller final population of M. incognita in CE-31 and may contribute to the high resistance of this cowpea cultivar against infection and colonization by this nematode species.