Multidimensional interplay between Xanthomonas oryzae TALEs and the rice genome

Rice is one of mankind's most important crops. Xanthomonas oryzae infects rice and can lead to high yield losses. A better understanding of the interplay between the two is of great importance for creating resistant crops and ensuring human nutrition. Since there are constant adaptations between host and pathogen in nature, a constant evaluation of the pathogen's arsenal of weapons is necessary. The virulence of many Xanthomonas strains is based on the secretion of transcription activator-like effectors (TALEs). They are secreted by a type III secretion system directly into plant host cells, which results in the transcription of target genes in the plant cells and thus supports the multiplication of Xanthomonas during infection. To decode the TALE arsenal in Xo, Nanopore sequencing was established. For this, a method for purification of high molecular-weight genomic DNA from Xanthomonas oryzae, using magnetic nanoparticles, was developed. It enabled the assembly of the genome of Xoostrain, PXO35, which was not possible, due to long repetitive TALE gene clusters, before. The genomic data of this strain revealed the participation of insertion sequences (IS) in the evolution of TALE clusters. To identify TALE-induced rice genes, a time-resolved expression analysis of Xanthomonas oryzae TALE target genes was performed. This revealed different expression characteristics for different TALE targets. One particular target gene, OsPHO1;3, a phosphate exporter from the SPX-EXS domain-containing protein family, was analyzed in more detail. It is induced by TalAO from Asian Xoo and was shown to play a crucial role in the infection of Xoo on phosphate-starved rice. This research has advanced the understanding of Xo-rice interaction at genetic and molecular levels, paving the way for novel research opportunities in crop improvement and disease resistance.