The sugar beet germplasm line EL10 is amendable to agroinfiltration-mediated transient expression with a capacity to achieve high levels of transgene expression in the leaf.

Abstract

Since discovering Agrobacterium tumefaciens has the distinctive capacity to incorporate a specified part of their transfer-DNA (T-DNA) into the genome of plants, the bacteria has been used extensively to genetically transform into crops agronomically important traits such as disease resistance, herbicide tolerance, and increased nutrition and yield. While Agrobacterium mediated plant transformation has proven its worth to crop enhancement and breeding platforms, some crop species such as sugar beet are recalcitrant to agrobacterium mediated transformation or transformation events are so infrequent that it makes it cost/time prohibitive for most plant biology labs to pursue. Therefore, determining the factors influencing efficient agrobacterium transformation in sugar beet would prove useful in the establishment of sugar beet transformation pipelines. Here, we report on the identification of a sugar beet germplasm ‘EL10’ (USDA-ARS PI 628755) that is amendable to agroinfiltration-mediated transient expression and is capable of achieving high levels of transgene expression in the leaf. Factors influencing efficient agroinfiltration were investigated including different strains of Agrobacterium, media composition, bacteria/plant co-incubation and plant growth conditions. Furthermore, by incorporating optimal promoter/5′-leader and terminator elements into the transgene T-DNA cassette, a significant reduction in transgene silencing was observed allowing for high expression of transgene to be maintained for as long as 5 weeks after agroinfiltration. The significance of ‘EL10’ germplasm (and not other sugar beet germplasm lines investigated) having the ability to be transiently transformed by Agrobacterium tumefaciens will also be discussed. Overall, the results presented will aid in the establishment of a routine agroinfiltration-mediated transient method for sugar beet.