cDNA-AFLP analysis of gene expression changes in apple trees induced by phytoplasma infection during compatible interaction

peer reviewedAbstract In order to gain insight into molecular and physiological changes in apple trees during compatible interaction with two ‘Candidatus Phytoplasma mali’ strains (AP and AT), cDNA-Amplified Fragment Length Polymorphism (cDNA-AFLP) technique was used. A rootstock of apple (MM106) susceptible to ‘Ca. P. mali’ was used to extend the range of the potential host responses by the maximum number of identified genes that will be deregulated by phytoplasma in apple. Gene expression comparisons were studied in three directions: healthy versus infected samples, symptomatic versus nonsymptomatic sample, and AP-infected versus ATinfected sample. Forty-five genes whose steady-state levels of expression significantly changed in response to phytoplasma infection were identified. Among their partial cDNA sequences, only 27 showed similarity to DNA or protein data bases; of these, 18 were related to known genes in plants, and the rest were related to unknown or hypothetical proteins. Eighteen out of 45 did not show any similarity with sequences in data bases (potential novel genes). Quantitative real-time RT-PCR (qRT-PCR) was used to confirm differential expression of AFLP identified genes, and showed the similar profile expression for 11 known genes among 18, and for 13 unknown, hypothetical or novel genes among 27. Changes in gene expression involved a wide spectrum of biological functions, including processes of metabolism, cell defence, senescence, photosynthesis, transport, transcription, signal transduction and protein synthesis. This is the first study of global gene profiling in plants in response to phytoplasma infections using cDNA-AFLP, and a model is proposed to explain the mode of action of the ‘Ca. P. mali’ in apple

Identification of host genes potentially implicated in the "Malus pumila, rootstock MM106" – "Candidatus Phytoplasma mali" interactions

Apple proliferation (AP) is one of the most serious diseases of apple trees in Europe. It is caused by a phytoplasma, ‘Candidatus Phytoplasma mali’. The goal of the present study was to analyze transcriptional profiles of Malus pumila during infection by ‘Ca. P. mali’ using cDNA-Amplified Fragment Length Polymorphism (cDNA-AFLP) technique in order to gain insight into molecular and physiological changes in diseased plants. We used a rootstock of apple (MM106) susceptible to ‘Ca. P. mali’ to maximise the range of the potential host responses, and two strains (AP and AT) of the pathogen. Gene expression comparisons were studied in 3 categories of plant materials: healthy sample versus infected samples, symptomatic versus non-symptomatic sample, and AP-infected sample versus AT-infected sample. Forty-five genes whose steady-state levels of expression significantly changed in response to phytoplasma infection were isolated and identified. Of 45 partial cDNA sequences, twenty-seven showed similarity to international DNA or protein data bases. Of these, 18 were previously characterized in plants (the rest was related to unknown or hypothetical proteins). Eighteen out of 45 did not show any similarity with sequences in data bases, and so may be present novel genes. The majority of fragments were differently expressed between healthy sample and infected samples (fewer differences between symptomatic and non-symptomatic samples, or between the samples infected by different strains of phytoplasma). Quantitative Real-time RT-PCR (qRT-PCR) was used to confirm differential expression of sequences isolated by cDNA-AFLP. We chose the most stable reference housekeeping genes (GAPDH and actin) for normalisation of our data. The gene expression ratios were calculated by means of ΔΔCt method. Consequently, the second methodology (qRT-PCR) showed the similar profile expression as primary elucidation technique (cDNA-AFLP) for 11 known genes (between 18) and 13 unknown, hypothetical or novel genes (between 27). Changes in gene expression involved a wide spectrum of biological functions, including processes of metabolism, cell defence, senescence, photosynthesis, transport, transcription, signal transduction and protein synthesis. The possible effect of phytoplasma infection on these processes and their relationships with disease development, symptom appearance and probably plant defence system is discussed. A model is proposed to explain the mode of action of the ‘Ca. P. mali’ in its host plant, apple tree. This is the first study of global gene profiling in plants in response to phytoplasma infections using cDNA-AFLP

Effect of some fungicides against the growth inhibition of Sclerotinia sclerotiorum mycelial compatibility groups

Sclerotinia sclerotiorum (Lib.) de Bary, the causal agent of Sclerotinia stem rot, is one of the most important pathogens of Brassica napus L. in northern Iran. In this study, 13 mycelial compatibility groups (MCGs) of the fungus were identified among 31 isolates sampled from four regions of Mazandaran province, Iran. Effective fungicides are useful in the integrated management of the disease. So, the effect of tebuconazole, propiconazole, cyproconazole, and Rovral-TS at five doses (0.0001, 0.001, 0.01, 0.1, and 1 ppm) was studied on the growth inhibition of S. sclerotiorum as in vitro tests. Maximum inhibition (100%) of S. sclerotiorum mycelial growth was obtained by the highest dose (1 ppm) of all tested fungicides, as well as by the doses of 0.1 and 0.01 ppm of propiconazole, cyproconazole, and tebuconazole. In this investigation, the reaction of S. sclerotiorum isolates belonging to different MCGs was evaluated against tebuconazole, propiconazole, cyproconazole, and Rovral-TS at their EC50 ranges. The results revealed that there was high variation of S. sclerotiorum MCGs against different fungicides. The inhibition percentage varied between 4.29% and 71.72%

First insight into genetic diversity and population structure of the Caucasian wild apple (Malus orientalis Uglitzk.) in the Hyrcanian forest (Iran) and its resistance to apple scab and powdery mildew

International audienc

Effect of some fungicides against the growth inhibition of Sclerotinia sclerotiorum mycelial compatibility groups

Sclerotinia sclerotiorum (Lib.) de Bary, the causal agent of Sclerotinia stem rot, is one of the most important pathogens of Brassica napus L. in northern Iran. In this study, 13 mycelial compatibility groups (MCGs) of the fungus were identified among 31 isolates sampled from four regions of Mazandaran province, Iran. Effective fungicides are useful in the integrated management of the disease. So, the effect of tebuconazole, propiconazole, cyproconazole, and Rovral-TS at five doses (0.0001, 0.001, 0.01, 0.1, and 1 ppm) was studied on the growth inhibition of S. sclerotiorum as in vitro tests. Maximum inhibition (100%) of S. sclerotiorum mycelial growth was obtained by the highest dose (1 ppm) of all tested fungicides, as well as by the doses of 0.1 and 0.01 ppm of propiconazole, cyproconazole, and tebuconazole. In this investigation, the reaction of S. sclerotiorum isolates belonging to different MCGs was evaluated against tebuconazole, propiconazole, cyproconazole, and Rovral-TS at their EC50 ranges. The results revealed that there was high variation of S. sclerotiorum MCGs against different fungicides. The inhibition percentage varied between 4.29% and 71.72%