Expression and regulation of programmed cell death-associated genes in systemic necrosis of PVYNTN susceptible potato tubers

Abstract

Virus-induced systemic necrosis accounts for great yield losses in potato (Solanum tuberosum) cultivars susceptible to the necrotic strain of potato virus Y (PVYNTN). To extend understanding of systemic necrosis, the tissue of healthy and PVYNTN-infected potato tubers (necrotic and non-necrotic) during storage was profiled for host gene expression using microarrays while virus concentration was determined using RT-qPCR. Comparison of non-necrotic tissue types revealed minor transcriptional differences, while tuber necrosis was characterized by high virus concentration and pronounced expression of defence response-associated genes. Creation of programmed cell death-associated gene ontology enabled assessment of expression and regulation of relevant differentially expressed genes implicated in the execution of plant programmed cell death. Vacuolar cell death and unfolded protein response to viral infection were implicated in the necrotic tuber tissue by transcriptional induction of genes possessing caspase-like activity and genes coding for endoplasmic reticulum chaperones and folding proteins. A meta-analysis, including all relevant publicly available gene expression datasets differing in genotype, pathogen interaction type and potato organ, revealed common defence responses associated with cell wall fortification, oxidative and biotic stress. The response in necrotic tissues of susceptible tubers resembled the hypersensitive response of resistant primary infected plants, but with hormonal signalling as an important differentiating factor. This study will be useful for in-depth analysis of programmed cell death regulation in plants by providing gene ontology. It specifically addresses the issue of systemic necrosis formation in PVYNTN-infected potato tubers during storage.