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Poster: Molecular & Cellular Plant-Microbe Interactions: Biotechnology


Transgenic Carrizo expressing ‘Candidatus Liberibacter asiaticus’ effector P235 displays Huanglongbing-like symptom and alters some gene expression
G. HAO (1) (1) usda/ars/hrl, U.S.A.

Candidatus Liberibacter asiaticus’ (Las) is the agent causing destructive citrus huanglongbing worldwide. A putative protein (P235) was identified in Las genome prophage region, which encodes a 123 amino-acid protein with a molecular weight of 14.19 kD. Green fluorescence protein (GFP)-fused with P235 appeared to accumulate in Nicotiana benthamiana cell nuclei by Agrobacterium-mediated transient expression, however, P235-GFP fusion protein in transgenic citrus targets the citrus chloroplast. P235 alone was constructed into a binary vector for citrus transformation. Over 40 independent transgenic Carrizo plants were obtained. Gene integration and expression were confirmed by molecular analysis. We observed that some P235-expressing Carrizo plants displayed HLB-like symptoms with leaf chlorosis and plant growth retardation. P235 expression levels, determined by RT-qPCR, correlated with HLB-like symptoms. Transcriptome analysis revealed that carbohydrate metabolism and biotic stress pathways were significantly affected in transgenic citrus expressing p235 effector. Higher transcript levels were determined for several stress-related genes involved in hormone metabolism and zinc ion binding. This is the first report that ‘Candidatus Liberibacter asiaticus’ encodes a protein that targets the chloroplast of plant cells and alters plant-host phenotypes.