2017 ASHS Annual Conference

Shoot regeneration is an important step for production of CRISPR-mediated mutant or transgenic plant production. We have used epicotyls of young seedlings of citrus as explants to study the effects of poplar auxin transport and endogenous auxin on shoot regeneration. First, we have observed that shoot regeneration is inhibited in basal ends of epicotyls cuttings of citrus seedlings. We have demonstrated that elevated endogenous auxin levels in the basal ends of the explants play a key role for the inhibition of shoot regeneration, and the poplar auxin transport is responsible for the elevated auxin levels in these cells. Meanwhile, our studies also show that blocking poplar auxin transport or reducing endogenous auxin concentrations in the epicotyl cuttings can significantly enhance shoot regeneration efficiencies. On the other hand, the elevated auxin levels enhance Agrobacterium infection efficiencies of the citrus explants. Based on these and other results, we have developed experimental manipulations to enhance efficiencies of Agrobacteirum infection and shoot regeneration of epicotyl cuttings of citrus.