Defence related molecular signalling in Potato

Potato production is hampered by several pathogens and is subjected to intense chemical based disease control, use of which also has undesirable consequences. Resistance breeding programs have also shown limited success. Hence, there is a need to develop durable disease resistance. Omics-techniques enable new layers of knowledge regarding molecules and their interactions mediating defence, which can contribute to identification of durable resistance sources. A novel network-based approach was used to improve the existing annotation of gene probes on the genome based microarray. Approximately 8000 unannotated probes received a new annotation. This improved annotation was used to assess genome wide changes in transcripts and proteins in response to treatments with resistance inducers, βamino butyric acid (BABA) and Phosphite based salt (Phi). Five thousand transcripts were significantly regulated 48 hours after 10 mM BABA treatment while one was regulated with 1 mM BABA. In coherence, 10 mM BABA but not 1 mM induced protection to the hemibiotroph Phytophthora infestans. No transcript was significantly regulated 48 hours after Phi treatment. Time course analysis revealed that Phi exerts a transient effect, as significant transcriptomic changes were observed only 3, 6 and 11 hours after treatment. In contrast, plants showed resistance to P. infestans even at 120 hours after Phi treatment. Phi and BABA dependent “Induced state” is not restricted to transcripts related to plant defence, as transcripts related to abiotic stress and primary metabolism were altered, while biotic stress and cell wall related proteins also increased in abundance. Furthermore, an in vitro based blackleg disease screening assay was developed to investigate Potato – Dickeya solani interactions. We show that salicylic (SA) and COI1 are necessary for defence in shoots and tubers to this necrotroph. We also screened a crossing population and identified “potential” D. solani susceptibility genes related to transcriptional regulation. We also show that while SA is necessary to restrict lesion development and pathogen growth in response to the necrotroph Alternaria solani, COI1 affects pathogen growth only. Transcriptomic analysis indicated that rapid defence response to A. solani involves biotic, abiotic and oxidative stress related transcripts regulated by SA and COI1. We identified a citrate binding protein, which is also induced by resistance inducers, as an SA-repressed susceptibility factor to A. solani. Finally, proteomics of PAMP triggered immunity revealed upregulation of oxidative stress proteins while proteins related to oxidative stress tolerance, GTP binding activity were specifically upregulated in effector triggered immunity interactions.