Journal of Citrus Pathology

Citrus greening or huanglongbing (HLB) is a devastating disease of citrus, and poses a major threat to the citrus industry in the United States (1, 2). Candidatus Liberibacter asiaticus has been known to be associated with HLB in the United States (3, 4).  Unsuccessful attempts to culture Ca. L. asiaticus have notably hampered efforts to understand its biology and pathogenesis mechanism despite some limited progresses in culturing.  In order to characterize the putative virulence factors, we expressed putative virulent factors in Nicotiana benthamiana.   Totally 24 putative virulent factors are being tested with most of them containing signal peptides. By transient expression of the candidates using TMV vector in N. benthamiana, we can screen the genes influencing plant development and morphology. Meanwhile, transformation of candidate genes into N. benthamiana driven by 35S promoter and phloem specific promoter respectively will further verify the function of putative virulence factors. Identification and characterization of the various virulence factors in Ca. L. asiaticus will advance the understanding of the biology and pathogenicity of the pathogen.