ThLBD11 negatively regulates downstream target genes during salt stress in Tamarix hispida

The Lateral Organ Boundaries Domain (LBD) transcription factors play a significant role in root development and abiotic stress in plants. In a previous study, the LBD family gene ThLBD11 was cloned and characterized from Tamarix hispida and is positioned at the second layer of the salt stress gene regulatory network in T. hispida, suggesting that ThLBD11 might play a role in the salt stress process.

We investigated the salt tolerance function and regulatory mechanisms of ThLBD11 using multiple sequence alignment, phylogenetic tree analysis, biochemical staining, physiological indicators, yeast one-hybrid, electrophoretic mobility shift assay, β-Glucuronidase (GUS) histochemical analysis, Gene Ontology enrichment analysis, chromatin immunoprecipitation assay (ChIP) and RT-qPCR.

In this study, ThLBD11 was overexpressed in T. hispida. Under salt stress, the overexpressing lines exhibited elevated antioxidant enzyme activity, reduced cellular damage and regulated ion homeostasis. Results of the yeast one-hybrid, electrophoretic mobility shift assay and GUS histochemical analysis showed that ThLBD11 was able to bind specifically to the CGGC cis-element. By integrating Gene Ontology enrichment analysis and promoter CGGC element counts, two downstream target genes (ThAHL27 and ThATPD) of ThLBD11 in the gene regulatory network were confirmed. The RT-qPCR and ChIP-PCR results indicated that ThLBD11 negatively regulated the expression of ThAHL27 and ThATPD by binding directly to their promoter fragments containing the CGGC motif.

ThLBD11 acts as a positive regulator of salt stress tolerance in T. hispida by inhibiting the expression of ThAHL27 and ThATPD. These findings contribute to the understanding of the regulatory mechanism of salt stress adaptation in T. hispida.