Graduate Research Assistant University of Florida GAINESVILLE, Florida
Body of Abstract: Plants rely on the innate immune system to defend themselves against pathogens. Both external signals from invading microbes and internal signals generated by the plant activate the plant’s immune system. The plant may also develop subsequent whole-plant resistance after initial induction of pattern- or effector-triggered immunity (PTI/ETI), which is known as systemic acquired resistance (SAR). Extracellular nicotinamide dinucleotide (NAD) and NAD phosphate (eNAD(P)) function as endogenous mobile signals in Arabidopsis thaliana that can activate SAR and induce resistance to pathogens. Previously, we showed that the L-type clade VI lectin receptor kinase, LecRK-VI.2, functions as a potential receptor of eNAD(P) in Arabidopsis. We are developing a Nicotiana benthamiana (tobacco)-based complementation assay to rapidly test other plant LecRK orthologues. Our hypothesis is that the eNAD(P)-induced defense signaling pathway is conserved in diverse crop plant species. By knocking out the eNAD(P) receptors in tobacco, we can test the activity of the LecRK orthologues via Agrobacterium-mediated transient expression. We have found that NAD not only induces the PR1 and LecRK-VI orthologue gene expression but also strong resistance against Pseudomonas syringae pv. tomato DC3000 in tobacco, suggesting that eNAD(P) may play a similar role in tobacco and that tobacco contains the necessary signaling components of the eNAD(P) signaling pathway. CRISPR/Cas9 will be used to knock out the two tobacco LecRK-VI orthologues. LecRK orthologues from crop plant species will then be transiently expressed in the knockout mutant to test their potential involvement in eNAD(P) signaling. For each potential eNAD(P) receptor orthologue, NAD binding activity of the extracellular domain will also be determined. This work aims to broaden the knowledge of SAR in plants and provide a foundation for the development of more resilient crop cultivars.