Rhizobium rhizogenes reprograms transcription in Cucurbita pepo hairy roots. Lessons learned from metabolic engineering in hairy roots: insights into the extent of transcriptome and metabolic profile changes caused by Rhizobium-mediated plant transformation in Cucurbitaceae species

Cucurbitacins are a structurally diverse type of highly-oxygenated triterpenoids categorized into 17 groups. Cucurbitacins were originally described in the Cucurbitaceae family, but have since been found in 15 taxonomically distant plant families. Cucurbitacin B, D, E and I are the most widespread amongst the Cucurbitaceae and they have both important biological and pharmacological activities. In this paper, we use Cucurbita pepo hairy roots as a platform to boost production and alter cucurbitacin structures by metabolic engineering to potentially provide new or more desirable bioactivities. We report that infection with Rhizobium rhizogenes reduces the levels of cucubitacins in the resulting hairy roots and that the transcriptome is extensively reprogramed. We conclude that hairy roots have the potential to be metabolically engineered, but that due to the apparent extensive transcriptome repogramming, hairy roots need to be empirically evaluated for each individual metabolite.