# Heterologous Expression of Sorghum bicolor PIP1-3 Gene Improves Drought Tolerance in Arabidopsis and Rapeseed

## TL;DR

This study shows that the SbPIP1-3 gene from sorghum improves drought tolerance in Arabidopsis and rapeseed by enhancing water transport and stress responses.

## Contribution

The novel contribution is demonstrating the functional role of SbPIP1-3 in improving drought tolerance through heterologous expression in model plants.

## Key findings

- SbPIP1-3 overexpression in yeast, Arabidopsis, and rapeseed improved survival under osmotic stress.
- Transgenic plants showed enhanced antioxidant activity and reduced H2O2 accumulation under drought.
- Drought-responsive genes and pathways were significantly upregulated in SbPIP1-3 overexpressing plants.

## Abstract

Aquaporins are key membrane proteins that mediate water transport in plants and are indispensable for maintaining cellular water homeostasis and normal physiological processes. This study investigated the function of SbPIP1-3, an aquaporin gene isolated from drought-tolerant Sorghum bicolor. Bioinformatics analysis, subcellular localization, and heterologous expression of SbPIP1-3 were performed in Saccharomyces cerevisiae, Arabidopsis thaliana, and rapeseed. Sequence analysis revealed that SbPIP1-3 encodes a basic hydrophobic protein targeted to the plasma membrane, a finding further corroborated by subcellular localization assays. In yeast expression assays, SbPIP1-3-transformed strains retained viability under osmotic stress induced by 1.2 M mannitol, whereas non-transgenic control strains failed to survive. In Arabidopsis and rapeseed experiments, the SbPIP1-3 overexpression enhanced drought tolerance (improved germination, root growth, antioxidant enzyme activity, proline content, PSII repair capacity, and survival after drought–rewatering) and reduced intracellular H2O2 accumulation. Transcriptome profiling of drought-stressed transgenic Arabidopsis and control plants demonstrated significant upregulation of mostly stress-responsive pathways (e.g., MAPK signaling pathway and hormone signaling pathways) and key drought-tolerance genes (e.g., SNRK2-2, SOD1, APX3, GPX3, P5CS1). Collectively, these findings suggest that SbPIP1-3 enhances plant drought tolerance through the following mechanisms: improving transmembrane water transport efficiency to sustain cellular osmotic balance; activating the antioxidant defense system to increase enzyme activity and mitigate reactive oxygen species (ROS) accumulation; optimizing photosynthetic protection mechanisms to preserve the structural and functional integrity of PSII; and regulating the expression of stress-responsive signaling pathways and associated functional genes.