Double genetically modified symbiotic system for improved Cu phytostabilization in legume roots

Area of Science:

• Environmental Biotechnology
• Plant Science
• Microbial Genetics

Background:

• Excess soil copper (Cu) negatively impacts plant growth and poses human health risks.
• Legume-rhizobium symbioses are emerging as biotechnological tools for metal phytostabilization.
• Genetic modification of symbionts is crucial for developing metal-tolerant strains for effective phytostabilization.

Purpose of the Study:

• To engineer a double symbiotic system for enhanced copper phytostabilization.
• To improve copper tolerance and root accumulation in Medicago truncatula using genetic engineering.
• To assess the efficacy of genetically modified Ensifer medicae in conjunction with modified plants for copper rhizophytostabilization.

Main Methods:

• Developed composite Medicago truncatula plants expressing the Arabidopsis thaliana metallothionein gene mt4a in roots to boost copper tolerance.
• Created a genetically modified Ensifer medicae strain expressing Pseudomonas fluorescens copper resistance genes (copAB) under a nodulation promoter (nifHp).
• Inoculated modified plants with the engineered Ensifer strain and evaluated plant growth, nodulation, copper accumulation, and oxidative stress markers.

Main Results:

• Expression of mt4a in composite plants improved growth, nodulation, and copper tolerance, with reduced oxidative stress markers (ROS-scavenging enzymes, TBARS).
• Inoculation with genetically modified Ensifer enhanced root copper accumulation without increasing shoot copper levels.
• The double modified system significantly reduced metal translocation from roots to shoots, indicating effective rhizophytostabilization.

Conclusions:

• The engineered double symbiotic system, combining modified Medicago truncatula and Ensifer medicae, demonstrates significant potential for copper rhizophytostabilization.
• This approach effectively enhances plant copper tolerance and root sequestration, mitigating copper's deleterious effects in soils.
• The developed strategy offers a promising biotechnological solution for managing copper-contaminated soils and reducing associated environmental and health risks.