Abstract
Phytoplasmas are mycoplasma-like pathogens of witches’ broom disease, and are responsible for serious yield losses of Paulownia trees worldwide. The molecular mechanisms of disease development in Paulownia are of considerable interest, but still poorly understood. Here, we have applied transcriptome sequencing technology and a de novo assembly approach to analyze gene expression profiles in Paulownia fortunei infected by phytoplasmas. Our previous researches suggested that methyl methane sulfonated (MMS) could reverse the effects of the infection. In this study, leaf samples from healthy, infected, and both infected and methyl methane sulfonate treated plants were analyzed. The results showed that the gene expression profile of P. fortunei underwent dramatic changes after Paulownia witches’ broom (PaWB) phytoplasma infection. Genes that encoded key enzymes in plant-pathogen interaction processes were significantly up-regulated in the PaWB-infected Paulownia. Genes involved in circadian rhythm and hormone-related genes were also altered in Paulownia after PaWB infection. However, after the PaWB-infected plants were treated with MMS, the expression profiles of these genes returned to the levels in the healthy controls. The data will help identify potential PaWB disease-resistance genes that could be targeted to inhibit the growth and reproduction of the pathogen and to increase plant resistance.
Highlights
Paulownia witches’ broom (PaWB) disease is a devastating disease of Paulownia trees, which can result in significant economic losses over a large part of the world [1,2]
It has been reported that the disease is caused by an obligate biotrophic plant pathogen called phytoplasma, which belongs to the taxon “Candidatus Phytoplasma australiense” International Research Programme on Comparative Mycoplasmology (IRPCM), Phytoplasma Taxonomy Group 2004 [4]
Fragments of the 16SrDNA were detected in the midribs of the PFI and PFI-20 samples, but not in the PF and PFI-60 samples (Figure 2). These results indicated that the PaWB infected seedlings recovered a healthy morphology after treatment with an optional concentration of methyl methane sulfonated (MMS)
Summary
Paulownia witches’ broom (PaWB) disease is a devastating disease of Paulownia trees, which can result in significant economic losses over a large part of the world [1,2]. Infected plants develop a series of similar symptoms, such as witches’ brooms, short internodes, yellowing or reddening of leaves, phyllody, stunting and decline, virescence, sterile flowers and necrosis, and altered volatile production [3]. Phytoplasma are mycoplasma-like organisms that reside in the phloem sieve cells of a plant and are transmitted by phloem-sucking insects [5]. After residence, they can travel systemically through the pores of the sieve plates and appear to accumulate mainly in roots, developing leaves, and flowers. Phytoplasmas have no cell wall and are strictly biotrophic; they can survive only on living host cells and are quite difficult to study
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