Chimeral constructs that should enhance AMP effectiveness (designed by Goutam Gupta of Los Alamos National Lab) are being tested and are among the most promising transgenics we have created, along with thionin transgenics. Trees transformed with a chimera AMP showed remarkable resistance in citrus canker compared to control. These promising transgenic lines were replicated by grafting for HLB challenge. Transgenic Hamlin lines expressing thionin were grafted onto Carrizo for HLB challenge. Replicated transgenic Transgenic Carrizo lines expressing thionin, chimera and control were grafted with HLB infected rough lemon. Promising resistance to HLB was observed based on plant growth and phenotype. Las titer is being checked from root and new flush rough lemon leaves. Two new chimeral peptides from citrus genes only were developed and used to produce many Carrizo plants and Hamlin shoots which will be tested soon as part of the next generation of this project. To explore broad spectrum resistance, a flagellin receptor gene FLS2 from tobacco was used to transform citrus. Flagellins are frequently PAMPS (pathogenesis associated molecular patterns) in disease systems and CLas has a full flagellin gene despite having no flagella detected to date. The consensus FLS2 clone was obtained and used to transform Hamlin and Carrizo so that resistance transduction may be enhanced in citrus for HLB and other diseases. Reactive Oxygen Species (ROS) assay showed typical ROS reaction in transgenic Hamlin indicating nbFLS is functional in citrus PAMP-triggered immunity. Trees showed significant canker resistance to spray inoculation. To disrupt HLB development by manipulating Las pathogenesis, a luxI homolog potentially producing a ligand to bind LuxR in Las was cloned into binary vector and transformed citrus. Both transformed Carrizo and Hamlin were obtained. Further investigation are underway. In collaboration with Bill Belknap two new citrus-derived promoters have been tested using a GUS reporter gene and have been shown to have extraordinarily high levels of tissue-specific expression. The phloem-specific promoter was used to create a construct for highly phloem specific expression of the chimeral peptide using citrus genes only. Transgenic plants of PP-2 hairpins (for suppression of PP-2 through RNAi to test possible reduction in vascular blockage even when CLas is present) and of PP-2 directly are grafted in the greenhouse. 40 putative transgenic plants transformed with citGRP1 were tested by PCR and twenty two of them were confirmed with citGRP1 insertion. RNA was isolated from some and RT-PCR showed gene expression. Some transgenics with over-expression of citGRP1 had increased resistance to canker by detached leaf assay but do not appear as potent as some other AMPs. Transgenic Carrizo and Hamlin with peach dormancy genes show no evidence of enhanced or accelerated dormancy A Las �expressed gene with a nuclear-localization sequence has been identified and studied, including creating transgenic citrus that express this p235 gene. Carrizo transformed with this gene displays leaf yellowing similar to that seen in HLB-affected trees. Gene expression levels, determined by RT-qPCR amplification, correlated with HLB-like symptoms. P235 translational fusion with GFP shows the gene product binds to citrus chloroplasts. Antibodies (ScFv) to the Las invA and TolC genes, and constructs to overproduce them, were created by John Hartung under an earlier CRDF project. We have transgenic Carrizo reflecting almost 400 independent transgenic events and 17 different ScFv ready for testing. A series of AMP transgenics scions produced in the last several years continue to move forward in the testing pipeline. Many trees are in the field and some are growing well but are not immune to HLB. A large number of ubiquitin::D4E1 and WDV::D4E1 plants and smaller numbers with other AMPs are replicated and now in the field.