In vivo assembly of sorgoleone biosynthetic pathway and its impact on agroinfiltrated leaves of Nicotiana benthamiana

Authors: Pan, Zhiqiang - Peter; Bajsa-Hirschel, Joanna; Vaughn, Justin; RIMANDO, AGNES - Retired ARS Employee; Baerson, Scott; DUKE, STEPHEN - Retired ARS Employee

Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2020
Publication Date: 1/18/2021
Citation: Pan, Z., Bajsa Hirschel, J.N., Vaughn, J.N., Rimando, A.M., Baerson, S.R., Duke, S.O. 2021. In vivo assembly of sorgoleone biosynthetic pathway and its impact on agroinfiltrated leaves of Nicotiana benthamiana. New Phytologist. 230:683-697.

Interpretive Summary: Sorghum species are known to possess allelopathic properties by biosynthesis and release of biologically active compounds that repress the growth of weeds. Sorgoleone, a hydrophobic compound exuded from root hair cells of Sorghum spp., accounts for much of the allelopathic activity. We have identified and functionally characterized all the enzymes involved in the biosynthesis of this compound. In this report, we describe in vivo assembly of the pathway by transiently expressing all the genes simultaneously in a tobacco plant Nicotiana benthamiana. Sorgoleone, as produced in vivo, not only caused a severe necrotic phenotype, a characteristic of phytotoxicity, but also significantly impacted gene expression including genes associated with photosynthesis machinery, transcription factors, and the proteasome. The current study strongly suggests that stably transformed plants harboring transgenes encoding the sorgoleone biosynthetic enzymes will likely be capable of performing the de novo biosynthesis of sorgoleone. Work is underway to generate cereal plants expressing the genes for this compound using in-house cloned root-hair specific expression promoters for weeds management.

Technical Abstract: Sorgoleone, a hydrophobic compound exuded from root hair cells of Sorghum spp., accounts for much of the allelopathic activity. The enzymes involved in the biosynthesis of this compound have been identified and functionally characterized. To explore the possibility of producing sorgoleone in other species, a multi-gene DNA construct was prepared for the expression of genes required for sorgoleone biosynthesis in planta and deployed in Nicotiana benthamiana leaf tissues via Agrobacterium-mediated transient expression. The production of sorgoleone observed in agroinfiltrated leaves as detected by GC/MS resulted in the formation of necrotic lesions, indicating that the compound possesses significant phytotoxicity to these tissues. RNA sequencing profiling revealed significant changes in gene expression in the host plant during sorgoleone-induced necrotic lesion formation. Data analysis suggested that the compound impaired photosynthetic system as results of down-regulated gene expression for photosynthesis apparatus and elevated expression of proteasomal genes, which may play a major role in the phytotoxicity of sorgoleone.