Transcriptome Analysis of Potato Infected with the Necrotrophic Pathogen Alternaria solani

Abstract

Potato early blight is caused by the necrotrophic fungus Alternaria solani and can result in yield losses of up to 50% if left uncontrolled. At present, the disease is controlled by chemical fungicides, yet rapid development of fungicide resistance renders current control strategies unsustainable. On top of that, a lack of understanding of potato defences and the quantitative nature of resistance mechanisms against early blight hinders the development of more sustainable control methods. Necrotrophic pathogens, compared to biotrophs, pose an extra challenge to the plant, since common defence strategies to biotic stresses such as the hypersensitive response and programmed cell death are often beneficial for necrotrophs. With the aim of unravelling plant responses to both the early infection stages (i.e., before necrosis), such as appressorium formation and penetration, as well as to later responses to the onset of necrosis, we present here a transcriptome analysis of potato interactions with A. solani from 1 h after inoculation when the conidia have just commenced germination, to 48 h post inoculation when multiple cell necrosis has begun. Potato transcripts with putative functions related to biotic stress tolerance and defence against pathogens were upregulated, including a putative Nudix hydrolase that may play a role in defence against oxidative stress. A. solani transcripts encoding putative pathogenicity factors, such as cell wall degrading enzymes and metabolic processes that may be important for infection. We therefore identified the differential expression of several potato and A. solani transcripts that present a group of valuable candidates for further studies into their roles in immunity or disease development.

Transcriptome sequencing leads to an improved understanding of the infection mechanism of Alternaria solani in potato

“…At 24 h post inoculation of A. solani infection into a potato leaf, necrosis of the first epidermal cells on the adaxial side of the leaf has been observed. Similar to our study, symptoms appeared on the backside of a leaf that had been inoculated 24 h. However, Brouwer studied A. solani infection of potato leaves only for the first 48 h, and the interaction of genes in the late stage of infection was not clear [ 14 ]. A transcriptome analysis of the genes in potato and A. solani that exhibited interactions in the early infection stage showed that cell wall-degrading enzymes and metabolic processes may be important for early A. solani infection of potato [ 14 ].…”

“…Similar to our study, symptoms appeared on the backside of a leaf that had been inoculated 24 h. However, Brouwer studied A. solani infection of potato leaves only for the first 48 h, and the interaction of genes in the late stage of infection was not clear [ 14 ]. A transcriptome analysis of the genes in potato and A. solani that exhibited interactions in the early infection stage showed that cell wall-degrading enzymes and metabolic processes may be important for early A. solani infection of potato [ 14 ]. In our previous study, we reported that the effector proteins AsCEP112, AsCEP19 and AsCEP20, and play important roles in late-stage A. solani infection of potato leaves [ 15 , 16 ].…”

“…have focused primarily on plant responses to infection, the genes encoding proteins that interact between A. solani and its potato host have received little attention [ 13 ]. A. solani infection progression through a 48 time courseh has been reported [ 14 ]. At 24 h post inoculation of A. solani infection into a potato leaf, necrosis of the first epidermal cells on the adaxial side of the leaf has been observed.…”

“…However, transcriptome analyses based on the interaction between potato and A. solani have rarely been reported [ 14 ]. Only transcriptome analysis of potato interactions with A. solani , which was based observations taken from 1 to 48 h post inoculation has been reported, and the cell wall-degrading enzymes and metabolic processes may be important for A. solani infection of potato [ 14 ]. Furthermore, few reports have focused on the pathogenic effectors of A. solani in potato.…”

Detection of Alternaria solani with high accuracy and sensitivity during the latent period of potato early blight

“…RT-qPCR is believed the most sensitive method among DNA-based pathogen detection technologies (Ling et al, 2010;Duan et al, 2014;Moradi et al, 2014). Certain transcripts, particularly highly transcribed ones that are repetitively transcribed from the same DNA sequence, are much more abundant than their corresponding DNA under the same conidia condition (Brouwer et al, 2021). In theory, the sensitivities of RNA-based detection methods are far superior to those of DNA-based methods.…”