Molecular aspects of the Nicotiana benthamiana infection by Moniliophthora perniciosa as a new model system to investigate the Witches Broom Disease of cacao

Abstract

Despite the progress in understanding the Moniliophthora perniciosa pathogenesis of cacao (Theobroma cacao), there are still many knowledge gaps. The interaction between two non-model organism poses serious experimental restrictions because of their lifestyles and lack of biological resources. Moniliophthora perniciosa can be categorized into biotypes according to the particular host, with isolates of the C-biotype specific to Theobroma and from the S-biotype specific to Solanaceae, with seldom cross infection. The miniature tomato (Solanum lycopersicum) cultivar 'Micro-Tom' (MT) is susceptible to the S-biotype, and when inoculated, it presents typical infection symptoms with the hypertrophic overgrowth of shoots. We have used S-biotype infected-MT as a model system to investigate various aspects of the pathogenesis difficult to evaluate in cacao (physiology, yield effect, resistance). We showed that inoculating MT with the C-biotype did not induce the typical symptoms, but reduced the height of the plants as an incompatible interaction. Here, we propose to establish Nicotiana benthamiana (Nb) as a new model system to investigate the M. perniciosa pathogenesis and the defense response. We will use Dual RNA-seq and hormone quantification to characterize the infection, comparing a compatible interaction (Nb inoculated with the C-biotype) and incompatible (Nb inoculated with the S-biotypes). The data will also be compared with similar inoculations of MT. To investigate genetic factors associated with incompatibility of the S-biotype interaction with Nb based on the knowledge of immune receptors previously described in plants, we will use virus-induced gene silencing (VIGS) to silence genes encoding surface and cytoplasmatic immune receptors (PRRs and NLRs). This approach would enable to determine if the incompatibility of M. perniciosa is associated with virulence factors or not, and it will direct which type of receptors would be involved in recognizing the S-biotype by N. benthamiana. (AU)