# Identification, Transcriptome, and Proteome Analysis of Expansin-like Subfamilies in the Storage Root Across I. trifida (2x), Wild (4x, 6x) and Cultivated Sweet Potatoes

## TL;DR

This study identifies and analyzes expansin-like genes in sweet potato and its wild relatives, revealing their potential roles in storage root development.

## Contribution

The study provides the first comprehensive transcriptomic and proteomic analysis of expansin-like subfamilies in wild and cultivated sweet potatoes.

## Key findings

- EXLA and EXLB gene numbers vary across diploid, tetraploid, and hexaploid sweet potato strains.
- Downregulation of Iba6xEXLB2 and Iba6xEXLB1 may be linked to storage root swelling.
- Subcellular localization confirmed Iba6xEXLB2 and Iba6xEXLB8 are in the cell wall/membrane.

## Abstract

The expansin-like subfamilies (EXLA and EXLB) are vital for plant cell wall dynamics, but it remains uncharacterized in wild tetraploid and hexaploid Ipomoea batatas, and its role in the storage root (SR) development is poorly understood. In this work, we identified 4, 3, 3, and 3 EXLAs, alongside 11, 9, 13, and 8 EXLBs, in diploid I. trifida strain Y22, wild tetraploid I. batatas strain Y428B, and hexaploid I. batatas strain Y601, and cultivated sweet potato ‘Nancy Hall’, respectively. A comprehensive bioinformatic analysis of the expansin-like genes and proteins was performed to reveal their potential roles in SR development. Gene expression profiling showed that EXLA members were expressed during SR development, while approximately half of the EXLB members were expressed in Y22, Y428B (pencil root), Y601, and NH, respectively. Proteomic analysis (4D-DIA) detected 2, 1, 1, and 1 EXLAs, and 3, 3, 3, and 3 EXLBs in the mature SRs of the respective species. Integrated transcriptomic and proteomic analyses suggested that downregulating Iba6xEXLB2 and Iba6xEXLB1 may be associated with SR swelling in sweet potato. Furthermore, subcellular localization assays confirmed that Iba6xEXLB2 and Iba6xEXLB8 are localized to the cell wall/membrane. This study enhances the understanding of the expansin-like gene subfamily in sweet potato and its wild relatives and lays the groundwork for future functional studies on the role of expansin-like genes in SR development.