RNASeq analysis of transgenic Arabidopsis lines overexpressing Pisum sativum SUN gene
Nuclear-envelope bridging Linkers of Nucleoskeleton and Cytoskeleton complexes, composed of inner and outer nuclear membrane proteins, SUN and KASH, respectively, are known to regulate nuclear movement in plants during developmental events and symbiotic interactions. However, their role in plant-pathogen interactions, particularly during pea-powdery mildew interactions, is not known. Using a bioinformatics approach, we identified a single C-terminal SUN protein in pea, PsSUN. Knockdown of PsSUN via virus-induced gene silencing exhibited altered nuclear morphology with increased nuclear circularity and sphericity. In addition, PsSUN knockdown impaired the migration of host nuclei towards the site of fungal penetration and inhibited PM growth. Stable PsSUN overexpressing transgenics generated in Arabidopsis thaliana, similar to PsSUN knockdown, displayed altered nuclear morphology with reduced nuclear sphericity as well as deformation of the nuclear envelope. RNA-seq analysis revealed that overexpression of PsSUN resulted in the induction of several defense-related genes, including salicylic acid signalling genes. Additionally, PsSUN overexpression lines showed elevated levels of the defense hormone, salicylic acid, as well as enhanced resistance against the bacterial pathogen Pseudomonas syringae. Overall, our study provides novel insights into the functional role of pea SUN protein in mediating host nuclear movement in plant-pathogen interactions as well as in the transcriptional regulation of defense-related genes.