# Rhizomicrobiomes from Drought-Adapted Mediterranean Species Differently Alter Leaf Metabolome of Rosmarinus officinalis L. Under Reduced Water Availability

## TL;DR

This study explores how rhizomicrobiomes from drought-tolerant Mediterranean plants affect the leaf metabolism of rosemary under drought stress.

## Contribution

The study demonstrates that rhizomicrobiome transplantation can modulate leaf metabolites in rosemary under drought conditions.

## Key findings

- PL-RM increased lignans and stress signaling metabolites in rosemary leaves.
- JP-RM improved root-to-shoot ratio and sugar accumulation in leaves.
- RO-RM reduced defense-related metabolites and abscisic acid levels.

## Abstract

Rosmarinus officinalis L. is known for its drought tolerance; however, its growth is adversely affected by both mild and severe water stress. This study investigates the potential of rhizomicrobiome (RM) transplantation to strengthen water stress resilience. Three RMs derived from native plants—R. officinalis (RO), Pistacia lentiscus L. (PL), and Juniperus phoenicea L. (JP)—collected from a semi-arid Mediterranean garrigue were inoculated into R. officinalis subjected to severe drought stress for 30 days. Although RM transplantation did not result in an increase in biomass, it led to the accumulation of intermediates within the phenylpropanoid/coumarin pathway and significant source-specific alterations in other leaf metabolites. Specifically, PL-RM increased the abundance of lignans and stress signaling metabolites. JP-RM improved the root-to-shoot ratio and the sugar and sugar-alcohol accumulation in leaves. Both JP-RM and RO-RM treatments reduced the abundance of abscisic acid, cyclic GMP, and purine recycling pathways. Additionally, RO-RM decreased the abundance of fifteen defense-related metabolites, indicating a direct interference of the inoculum with the plant immune system. In conclusion, these findings suggest that targeted RM manipulation can be an effective strategy to modulate R. officinalis leaf metabolism.