RESUMEN
'Candidatus Phytoplasma mali' (Ca. P. mali) is the disease agent causing apple proliferation (AP), which has detrimental effects on production in many apple growing areas of Central and Southern Europe. The present study investigated transcriptional and biochemical changes related to the sugar metabolism as well as expression of pathogenesis-related (PR) protein genes in in vitro micro-propagated AP-infected and healthy control plantlets with the aim of shedding light on host plant response to 'Ca. P. mali' infection. Expression changes between infected and control plantlets were detected by quantitative real-time PCR analysis. The most significant transcriptional changes were observed for genes coding for pathogenesis-related proteins and for heat shock protein 70, as well as for some genes related to the sugar metabolism, such as a sorbitol transporter (SOT5), hexokinase, sucrose-phosphate synthase or granule bound starch synthase. Furthermore, biochemical analyses revealed that infected plantlets were characterized by a significant accumulation of starch and sucrose, while hexoses, such as glucose and fructose, and sorbitol were present at lower concentrations. In summary, the present analysis provides an overview of a gene set that is involved in response to phytoplasma infection and, therefore, it may help for a better understanding of the molecular mechanisms involved in phytoplasma-host plant interaction in apple.
Asunto(s)
Metabolismo de los Hidratos de Carbono/genética , Expresión Génica , Genes de Plantas , Malus/genética , Phytoplasma , Enfermedades de las Plantas/genética , Proteínas de Plantas/genética , Regulación de la Expresión Génica de las Plantas , Proteínas HSP70 de Choque Térmico/genética , Proteínas HSP70 de Choque Térmico/metabolismo , Hexosas/genética , Hexosas/metabolismo , Interacciones Huésped-Patógeno/genética , Malus/metabolismo , Malus/microbiología , Enfermedades de las Plantas/microbiología , Proteínas de Plantas/metabolismo , Reacción en Cadena en Tiempo Real de la Polimerasa , Almidón/genética , Almidón/metabolismo , Estrés Fisiológico/genética , Sacarosa/metabolismoRESUMEN
Apple proliferation (AP) represents a serious threat to several fruit-growing areas and is responsible for great economic losses. Several studies have highlighted the key role played by the cell wall in response to pathogen attack. The existence of a cell wall integrity signaling pathway which senses perturbations in the cell wall architecture upon abiotic/biotic stresses and activates specific defence responses has been widely demonstrated in plants. More recently a role played by cell wall-related genes has also been reported in plants infected by phytoplasmas. With the aim of shedding light on the cell wall response to AP disease in the economically relevant fruit-tree Malus × domestica Borkh., we investigated the expression of the cellulose (CesA) and callose synthase (CalS) genes in different organs (i.e., leaves, roots and branch phloem) of healthy and infected symptomatic outdoor-grown trees, sampled over the course of two time points (i.e., spring and autumn 2011), as well as in in vitro micropropagated control and infected plantlets. A strong up-regulation in the expression of cell wall biosynthetic genes was recorded in roots from infected trees. Secondary cell wall CesAs showed up-regulation in the phloem tissue from branches of infected plants, while either a down-regulation of some genes or no major changes were observed in the leaves. Micropropagated plantlets also showed an increase in cell wall-related genes and constitute a useful system for a general assessment of gene expression analysis upon phytoplasma infection. Finally, we also report the presence of several 'knot'-like structures along the roots of infected apple trees and discuss the occurrence of this interesting phenotype in relation to the gene expression results and the modalities of phytoplasma diffusion.
Asunto(s)
Pared Celular/metabolismo , Regulación de la Expresión Génica de las Plantas/genética , Malus/genética , Phytoplasma/fisiología , Enfermedades de las Plantas/microbiología , Proteínas de Plantas/genética , Cartilla de ADN , Glucosiltransferasas/genética , Glucosiltransferasas/metabolismo , Interacciones Huésped-Patógeno , Malus/crecimiento & desarrollo , Malus/microbiología , Modelos Biológicos , Especificidad de Órganos , Fenotipo , Floema/genética , Floema/crecimiento & desarrollo , Floema/microbiología , Filogenia , Hojas de la Planta/genética , Hojas de la Planta/crecimiento & desarrollo , Hojas de la Planta/microbiología , Proteínas de Plantas/metabolismo , Raíces de Plantas/genética , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/microbiología , ARN de Planta/genética , Regulación hacia ArribaRESUMEN
Grapevine root rot, caused by Armillaria mellea, is a serious disease in some grape-growing regions. Young grapevines start to show symptoms of Armillaria root rot from the second year after inoculation, suggesting a certain degree of resistance in young roots. We used a suppression subtractive hybridization approach to study grapevine's reactions to the first stages of A. mellea infection. We identified 24 genes that were upregulated in the roots of the rootstock Kober 5BB 24 h after A. mellea challenge. Real-time reverse-transcriptase polymerase chain reaction analysis confirmed the induction of genes encoding protease inhibitors, thaumatins, glutathione S-transferase, and aminocyclopropane carboxylate oxidase, as well as phase-change related, tumor-related, and proline-rich proteins, and gene markers of the ethylene and jasmonate signaling pathway. Gene modulation was generally stronger in Kober 5BB than in Pinot Noir plants, and in vitro inoculation induced higher modulation than in greenhouse Armillaria spp. treatments. The full-length coding sequences of seven of these genes were obtained and expressed as recombinant proteins. The grapevine homologue of the Quercus spp. phase-change-related protein inhibited the growth of A. mellea mycelia in vitro, suggesting that this protein may play an important role in the defense response against A. mellea.