Genome-wide identification of the Hordeum vulgare (L.) CASPL gene family and its diverse roles in response to drought and salt stress

Abstract

Casparian strip membrane domain proteins like (CASPL), exhibit profound associations with root development, stress responsiveness and mineral element uptake in plants. However, systematic characterization of the CASPL family in H. vulgare ( Hordeum vulgare ) and its involvement in drought and salt stresses remains unclear. In this study, a genome-wide identification and systematic analysis of the HvCASPL gene family was performed. Gene structure, conserved motifs, phylogenetic classification, duplication events, selective pressure, and cis-acting regulatory elements were comprehensively analyzed. Tissue-specific expression patterns and the expression responses of candidate HvCASPL genes to ABA, PEG6000-induced dehydration, and salt stress were further validated via RT-qPCR. In this study, 36 HvCASPL genes were identified and classified into five Groups. Gene structure and conserved motif analyses revealed that 94% HvCASPL members possess the typical CASP domain, variations in exon-intron and motif composition suggested functional divergence. Tandem duplication (TD) and whole-genome duplication (WGD) were identified as the primary driving force for HvCASPL family expansion, with purifying selection (Ka/Ks<1) maintaining sequence integrity. Promoter cis-element analysis revealed a complex regulatory network involving hormone, stress responses, and growth and development signaling. Tissue expression patterns showed that HvCASPL genes were significantly differentially expressed in different tissues, with HvCASPL12/19/22/23 showing higher expression levels in roots. Notably, RT-qPCR expression profiling on 14 selected genes from 36 HvCASPL family members demonstrated that eight HvCASPL genes ( HvCASPL5 , HvCASPL16 , and HvCASPL22 ) were significantly upregulated in response to ABA, PEG6000 and salt treatment. These transcriptomic findings indicate that the HvCASPL family has undergone functional diversification at the transcriptional level and exhibits distinct expression reprogramming under PEG-simulated dehydration and salt stress, implying their potential involvement in barley abiotic stress responses.