TAL Effector induced resistance to Xanthomonas

TAL Effector induced resistance to Xanthomonas

Report Date: 10/15/2014
Project: 555   Year: 2014
Category: Horticultural & Management
Author: Diana Horvath
Sponsor: Citrus Research and Development Foundation

This quarter we have continued to make progress on our transformation approaches: 1. Stable transformation in citrus using new vectors. We previously found that the original vector system used to create the Bs3 promoter constructs was contributing to low transformation efficiency in citrus, and switched to a pCAMBIA-based vector system. Two ProBs314EBE:avrGf2 transgenic plants created using the new vectors in citrus cultivar Carrizo have now been confirmed by PCR to contain the transgene, and these will be examined for appropriate gene expression by RT-PCR. An ongoing pipeline of transformants are being generated with the new vectors. To date a total of 2,056 putative transgenic shoots of grapefruit, sweet orange and Carrizo were screened for this period. Results show that no GUS positive has been observed for the sweet orange cultivar transformed with any of the constructs analyzed, however, 3 shoots were chimeric for the pCAMBIA2201:NosT:Bs3super::avrGF2 construct. In general, Grapefruit had a combined total of 12 and 41 shoots being GUS positive and chimeric for GUS, respectively for all constructs anlayzed while Carrizo citrange had 185 and 180 shoots being GUS positive and chimeric for GUS, respectively. These GUS and chimeric shoots will later be screened via PCR once rooted and transferred to soil for acclimatization. 2. Stable transformation in tomato test system: A tomato test system was previously designed and tested in which the 14 EBE promoter was fused to the avrBs4 gene capable of inducing a hypersensitive reaction in tomato. T1 generation of Bonny Best and Large Red Cherry transformed with ProBs3_14EBE:avrBs4 were screened for pathogenicity reaction with X. euvesicatoria strain (Race 9). Promising resistant transgenics have been selected for T2 generation analysis to confirm that this test system, in which resistance is induced by the effectors AvrBs3 and AvrHah1, is functional for conferring stably-transformed transgenic disease resistance.


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