title: A gene expression analysis of cell wall biosynthetic genes in Malus x domestica infected by 'Candidatus Phytoplasma mali'.
abstract: 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.
authors.affiliation: Research Centre for Agriculture and Forestry Laimburg, Laimburg 6, 39040 Auer/Ora (BZ), Italy. gea.guerriero@boku.ac.at
authors.forename: Gea
authors.initials: G
authors.lastname: Guerriero
authors.forename: Filomena
authors.initials: F
authors.lastname: Giorno
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Ciccotti
authors.forename: Silvia
authors.initials: S
authors.lastname: Schmidt
authors.forename: Sanja
authors.initials: S
authors.lastname: Baric
mesh_terms: D002473:Cell Wall / Q000378:metabolism*; D017931:DNA Primers; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D054884:Host-Pathogen Interactions; D027845:Malus / Q000235:genetics* / Q000254:growth & development / Q000382:microbiology; D008954:Models, Biological; D009928:Organ Specificity; D010641:Phenotype; D052585:Phloem / Q000235:genetics / Q000254:growth & development / Q000382:microbiology; D010802:Phylogeny; D045582:Phytoplasma / Q000502:physiology*; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000382:microbiology; D018749:RNA, Plant / Q000235:genetics; D015854:Up-Regulation
chemical_list: D017931:DNA Primers; D010940:Plant Proteins; D018749:RNA, Plant; D005964:Glucosyltransferases; C478648:cellulose synthase; C020570:1,3-beta-glucan synthase