# Functional Analysis of Tomato SPDS in Response to Osmotic Stress

## TL;DR

This study identifies and analyzes four SlSPDS genes in tomato, showing they help the plant tolerate drought and salt stress by boosting stress resistance.

## Contribution

The study functionally characterizes the SlSPDS gene family in tomato and demonstrates their role in abiotic stress tolerance through transgenic validation.

## Key findings

- Four SlSPDS genes were identified and analyzed for their stress response and localization in tomato.
- Overexpression of SlSPDS genes reduced wilting and chlorosis under drought and salt stress.
- Transgenic lines showed enhanced ROS scavenging capacity, improving stress tolerance.

## Abstract

What are the main findings?
Four SlSPDS genes were identified in tomato, and their characteristics, subcellular localization, and stress response patterns were systematically analyzed.Transient expression of SlSPDS affected polyamine contents in tomato, and overexpression transgenic tomato lines were generated to verify the function of SlSPDS.

Four SlSPDS genes were identified in tomato, and their characteristics, subcellular localization, and stress response patterns were systematically analyzed.

Transient expression of SlSPDS affected polyamine contents in tomato, and overexpression transgenic tomato lines were generated to verify the function of SlSPDS.

What is the implication of the main finding?
These findings clarify the potential role of the SlSPDS gene family in abiotic stress tolerance in tomato.This study provides a theoretical basis for the genetic improvement of stress resistance in Solanaceae crops.

These findings clarify the potential role of the SlSPDS gene family in abiotic stress tolerance in tomato.

This study provides a theoretical basis for the genetic improvement of stress resistance in Solanaceae crops.

Polyamines, such as spermidine (Spd), are small aliphatic amines that play critical roles in plant growth, fruit development, and stress responses. Spermidine synthase (SPDS) is the enzyme responsible for catalyzing Spd biosynthesis. However, the functional characterization of SPDS genes in tomato (Solanum lycopersicum) has been less studied. In this study, four SlSPDS genes (SlSPDS1-4) were identified and analyzed for their physicochemical properties, phylogenetic relationships, promoter cis-acting elements, subcellular localization, responses to various abiotic stresses, and effects on polyamine content in tomato leaves. Promoter analysis revealed the presence of multiple hormone and stress-responsive elements. Simultaneously, the overexpressing lines were subjected to osmotic stress treatment. Subcellular localization experiments demonstrated that SlSPDS1 and SlSPDS2 were distributed in both the nucleus and cytoplasm, while SlSPDS3 and SlSPDS4 were specifically localized to the nucleus. SlSPDS1-3 exhibited significant responses to high/low temperature stress, salt stress, and ABA stress. Meanwhile, only SlSPDS1 and SlSPDS4 exhibited responses to drought stress. Transient expression of SlSPDSs in tomato revealed changes in the accumulation levels of spermine, putrescine, tyramine, and tryptamine, whereas the contents of spermidine and phenethylamine showed no significant changes. Simultaneously, we successfully obtained four SlSPDS-overexpressing transgenic tomato lines, OE-SPDS1-4. Phenotypic analysis confirmed that these transgenic lines exhibited significantly reduced wilting and chlorosis compared with WT plants under drought and salt stress. Functional validation indicates that overexpression of these genes enhances reactive oxygen species (ROS) scavenging capacity in transgenic tomatoes, thereby potentially improving their tolerance to drought and salt stress. These findings highlighted the potential function of SlSPDS genes in tomato, providing valuable targets for improving stress tolerance.