Identification of the KNOX Gene Family in <i>Salvia miltiorrhiza</i> Revealing Its Response Characteristics to Salt Stress

Abstract

Salvia miltiorrhiza is a herbaceous plant that possesses significant medicinal value. Land salinization affects the growth of S. miltiorrhiza, resulting in a decline in its quality and yield. Knotted1-like homeobox (KNOX) genes are transcription factors that play important roles in plant growth and abiotic stress. The characteristics and functions of KNOX genes in S. miltiorrhiza remain unclear. Here, we identified ten KNOX genes in S. miltiorrhiza, all of which possess the characteristic four domains: KNOX1, KNOX2, ELK, and HD. These SmKNOXs were divided into two groups together with homologous genes. Cis-acting element analysis indicated all SmKNOXs contained elements associated with phytohormone, light, and stress response. The SmKNOXs show tissue-specific expression among roots, stems, leaves, and flowers. We assessed the response of the SmKNOXs to salt stress using quantitative RT-PCR analysis. Notably, SmKNOX4 expression significantly decreased within 24 h of salt exposure, while SmKNOX1, SmKNOX2, SmKNOX3, SmKNOX8, and SmKNOX9 showed significant increases. The expression of SmKNOX1, SmKNOX2, and SmKNOX3 was significantly positively correlated with that of their target genes, GA20ox1 and S11 MYB. These findings suggest that SmKNOXs and their target genes respond to salt stress, providing a foundation for studies of SmKNOXs and the potential genetic improvement of S. miltiorrhiza.

Keywords

• <i>Salvia miltiorrhiza</i>
• KNOX gene family
• subcellular localization
• expression analysis
• salt stress
• target genes