Rhizosphere bacteria containing ACC deaminase decrease root ethylene emission and improve maize root growth with localized nutrient supply

Localized nutrient supply can enhance maize root proliferation, but also increase root ethylene production. Whether engineering ethylene signalling in the rhizosphere can further enhance root growth and nutrient uptake remains unknown. Here, field and column experiments for maize (Zea mays. L) were designed as different nutrient treatments (broadcast or localized nutrient supply containing ammonium and phosphorus) with or without inoculation with rhizobacterium Variovorax paradoxus 5C-2 containing the 1-aminocyclopropane-1-carboxylate (ACC) deaminase. Rhizobacterial inoculation increased shoot biomass by 12% and root length density by 50% with localized nutrient supply. Meanwhile, localized nutrient supply increased root ethylene production by 54% compared with broadcast, and rhizobacterial inoculation prevented the increase in root ethylene. Reduced root ethylene production following V. paradoxus 5C-2 inoculation was highly associated with a greater proportion of fine root proliferation under localized nutrient supply, which may account for the increased nitrogen and phosphorus uptake. Our work sheds light on the understanding of the interactions between root and microbe through taking hormone into consideration to dissect the relationship between below ground and above ground. It is useful to explore the strategy of soil-crop management by introducing rhizosphere microorganisms to regulate plant ethylene signal and then benefit sustainable agriculture.

Automated summary

This study found that inoculation with rhizobacteria can increase shoot biomass and root length density of maize under localized nutrient supply conditions, while also preventing the increase in root ethylene production, leading to enhanced fine root proliferation and nutrient uptake. The findings highlight the potential of regulating plant ethylene signaling through rhizosphere microorganisms for sustainable agriculture practices.