Ali Lab



Current Projects

Lab people






Basic research in plant-microbe interaction.

i. Characterization of Phytophthora spp. isolated from ornamental crops in central Florida. Various Phytophthora spp are most frequently isolated from a variety of foliar and woody ornamental plants in central Florida.   Based on morphological characteristics and previous pathological history of a particular crop, these isolates are tentatively identified to the species level.  However, it is important to accurately identify these species using molecular analyses.  Many isolates of different Phytophthora spp that are resistant to Mefenoxam, a commonly used fungicide for controlling Phytophthora, have been reported.  For managing fungicide-resistance, it is important to determine prevalence of Mefenoxam resistant isolates of Phytophthora strains on ornamental crops.  Using molecular phylogenetic analyses, we are characterizing various Phytophthora isolatesisolated from 17 genera of ornamental crops. Fungicide sensitivity assays against several commonly used fungicides will be conducted using standard procedures.

ii. Calcium and auxin signaling in plant microbe interaction: Plants use two major immunity systems to defend themselves against pathogens.  In one system, conserved microbe/pathogen-associated molecular patterns (MAMP/PAMP) are recognized by plants through “Pattern Recognition Receptors” (PRRs) leading to the activation of defense responses (see Fig on right). Pathogens inactivate PAMP-triggered immunity by delivering virulent disease causing effectors proteins into cells.  Plants counteract by recognizing these effectors through resistance (R) proteins, which leads to a more rapid and robust defense system called effector-triggered immunity.  My lab conduct research on certain aspects of both these pathways. Arabidopsis is a resource-rich model system for conducting basic plant-microbe interaction studies. Calcium and auxin are known to play important role in plant defense signaling.  Currently, the molecular mechanisms of how calcium and auxin affect defense responses are not very well known.  Calcium and its ubiquitous sensor calmodulin (CaM) play important roles in plant defense.   In order to investigate the role of Ca2+/CaM in plant defense, we have identified several CaM-binding proteins that are likely involved in plant-pathogen interaction.   Recently, others and we have shown that CAMTA3 (calmodulin-binding transcription activator 3 ; also called AtSR1 for Arabidopsis thaliana Signal Response 1 ) and its rice homolog (OsCBT) negatively regulate plant immunity.  Loss-of-function camta3 mutants display constitutively elevated SA, PR genes and resistance to bacteria.  Our group is currently investigating several important questions related to calcium and auxin signaling using molecular, cell biological, genetic and physiological approaches.  Understanding the calcium and auxin-signaling pathway components can lead to engineering crops for enhanced resistance against plant pathogens. 

iii. Y2H hybrid screen for identifying proteins that interact with Phytophthora effector proteins.Bioinformatics analyses of genome sequences of several Phytophthora species have revealed an extraordinarily large number of secreted disease effector proteins.  Some of these effectors function in the plant extracellular spaces (apoplasts), whereas others are injected inside plant cells and are suggested to attenuate plant defense responses for promoting pathogen colonization.  To understand the molecular basis of how the Phytophthora effectors alter plant physiology, it is important to identify their targets in host plants, and to understand their role in pathogenesis. Using several molecular and cell biological approaches, we are investigating several questions about how Phytophthora cause disease in host plants. 



A simplified schematic overview of the innate immune systems in plants.  For an explanation, see text(ii).  AtSR1 (Arabidopsis thaliana Signal Response1); PRR (Pattern Recognition Receptor); EDS1 (Enhanced Disease Susceptibility1 ); MAPK (Mitogen-Activated Protein Kinase); TTSS (Type III Secretion System); TIR-NBS-LRR (Toll/Interleukin-1 Receptor-Nucleotide Binding Site-Leucine-Rich Repeats)