Team:Bio Without Borders

(Shhhhhh!) Silencing genes in Diaphorina citri to Combat Huanglongbing Disease in Citrus

Huanglongbing (HLB) is a disease that has decimated citrus crops worldwide. It occurs when the trees are infected with the bacterium Candidatus liberibacter asiaticus (CLas), resulting in dysregulation of the immune system of the host citrus plants. It is introduced into the citrus plant when the asian citrus psyllid, Diaphorina citri, feeds on the plant’s sap. CLas migrates from the insect gut into the phloem through the psyllid’s saliva. Infected trees produce inedible green fruit, and slowly die.

Farmers have responded by using more pesticides in an effort to kill the psyllids. Pesticides and antibiotics have disastrous long term effects in the form of ecological destruction and creation of antibiotic resistant soil bacteria. We wanted to find a more ecologically-friendly solution!

We improved upon the work of the TecCEM 2017 iGEM team, using a modification of their system to silence critical psyllid development genes using siRNA. We targeted chitin synthase and superoxide dismutase, two genes critical for psyllid development. We also wanted to explore the use of whole bacteria carrying the siRNA instead of purified siRNA to treat plants, which would simplify production and delivery. We envision delivery via a trap that contains the RNase minus E.coli/siRNA-producing cassette. We hope to slow down the spread of CLas through the reduction of psyllid populations.

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