Plant hairy roots enable high throughput identification of antimicrobials against Candidatus Liberibacter spp.

Sonia Irigoyen,Manikandan Ramasamy,Michael S Irey,Kranthi K Mandadi,Shankar Pant,Michael V Kolomiets,Renesh Bedre,Prakash Niraula,Zachary Gorman,Diann Achor,Carlos A Avila,Corinne Laughlin,Denise Rossi,Mamoudou Sétamou,Meena Gurung,Amit Levy,Ismael E Badillo-Vargas

doi:10.1038/s41467-020-19631-x

Abstract

A major bottleneck in identifying therapies to control citrus greening and other devastating plant diseases caused by fastidious pathogens is our inability to culture the pathogens in defined media or axenic cultures. As such, conventional approaches for antimicrobial evaluation (genetic or chemical) rely on time-consuming, low-throughput and inherently variable whole-plant assays. Here, we report that plant hairy roots support the growth of fastidious pathogens like Candidatus Liberibacter spp., the presumptive causal agents of citrus greening, potato zebra chip and tomato vein greening diseases. Importantly, we leverage the microbial hairy roots for rapid, reproducible efficacy screening of multiple therapies. We identify six antimicrobial peptides, two plant immune regulators and eight chemicals which inhibit Candidatus Liberibacter spp. in plant tissues. The antimicrobials, either singly or in combination, can be used as near- and long-term therapies to control citrus greening, potato zebra chip and tomato vein greening diseases.

Highlights

A major bottleneck in identifying therapies to control citrus greening and other devastating plant diseases caused by fastidious pathogens is our inability to culture the pathogens in defined media or axenic cultures
Since Candidatus Liberibacter spp. (CLso and Candidatus Liberibacter asiaticus (CLas)) are phloem-limited pathogens, we tested whether plant hairy roots, which possess intact vasculature[24,25,26], could sustain their growth
Combined with the Sanger-sequencing confirmatory analysis, our results sufficiently demonstrate the presence of Candidatus Liberibacter solanacearum (CLso)/CLas in the hairy roots and suggest that the CLso/CLas can be maintained in plant hairy roots like normal infected plant roots

Summary

Introduction

A major bottleneck in identifying therapies to control citrus greening and other devastating plant diseases caused by fastidious pathogens is our inability to culture the pathogens in defined media or axenic cultures. CLas and CLso share some commonalities, such as their unculturable nature, genomic attributes, and lifestyles as psyllid-vectored and phloem-limited bacteria[7,8,9,10] These and other diseases caused by fastidious plant pathogens are major threats to global agriculture and food security. Using the microbial hairy roots, we conduct antimicrobial screening leading to the discovery of multiple genetic and chemical therapies that effectively suppress Candidatus Liberibacter spp. in plant tissues

Methods

Results

Conclusion