# Identification and Bioinformatics Analysis of the HSP20 Family in the Peony

## TL;DR

This study identifies and analyzes HSP20 genes in peony to understand their role in heat tolerance, which could help improve the plant's resilience to heat stress.

## Contribution

The first genome-wide identification and analysis of PsHSP20 genes in peony, revealing their structure, regulation, and heat-responsive expression.

## Key findings

- 58 PsHSP20 genes were identified and classified into 11 subfamilies with conserved domains and localization patterns.
- Transcriptomics showed 48 PsHSP20 genes rapidly upregulated under heat stress, with PsHSP20-12, -34, and -51 showing the highest induction.
- Promoters of PsHSP20 genes are enriched in stress-responsive elements and linked to co-expressed partners in heat response and ER protein processing.

## Abstract

Background: The peony (Paeonia suffruticosa Andr.), a globally valued woody ornamental species, suffers severe heat-induced floral damage that compromises its horticultural value. While the HSP20 proteins are critical for plant thermotolerance, their genomic organization and regulatory dynamics remain uncharacterized in the peony. This study aims to systematically identify the PsHSP20 genes, resolve their molecular features, and elucidate their heat-responsive expression patterns to enable targeted thermotolerance breeding. Methods: The genome-wide identification employed HMMER and BLASTP searches against the peony genome. The physicochemical properties and protein structures of the gene family were analyzed using online websites, such as Expasy, Plant-mPLoc, and SOPMA. The cis-regulatory elements were predicted using PlantCARE. Expression profiles under different times of 40 °C heat stress were validated by qRT-PCR (p < 0.05). Results: We identified 58 PsHSP20 genes, classified into 11 subfamilies. All members retain the conserved α-crystallin domain, and exhibit predominant nuclear/cytoplasmic localization. Chromosomal mapping revealed uneven distribution without lineage-specific duplications. The promoters were enriched in stress-responsive elements (e.g., HSE, ABRE) and in 24 TF families. The protein networks linked 13 PsHSP20s to co-expressed partners in heat response (GO:0009408) and ER protein processing (KEGG:04141). Transcriptomics demonstrated rapid upregulation of 48 PsHSP20s within 2 h of heat exposure, with PsHSP20-12, -34, and -51 showing the highest induction (>15-fold) at 6 h/24 h. Conclusions: This first genome-wide study resolves the architecture and heat-responsive dynamics of the PsHSP20 family. The discovery of early-induced genes (PsHSP20-12/-34/-51) provides candidates for thermotolerance enhancement. These findings establish a foundation for molecular breeding in the peony.