Genome-Wide identification and expression analysis revealed the potential role of CHS gene family responding to atmospheric pressure stress in Saussurea involucrata

Saussurea involucrata (S. involucrata) is a traditional Chinese medicinal herb that grows in alpine environment. It is classified as endangered due to its long growth cycle and the illegal harvesting of wild resources. Flavonoids, as the main plant metabolites, play an important role in protecting land plants from various environmental stresses. The chalcone synthase (CHS) gene family is the first rate-limiting enzyme in the synthesis of flavonoids, which play an important role in plant growth, development and adaptation to the environment. Although there has been comprehensive characterization of CHS genes in multiple plant species, their physiological and genetic regulatory mechanisms within S. involucrata are insufficiently characterized. We identified 10 CHS genes from the genome of S. involucrata, unevenly distributed across five chromosomes, and they were divided into five groups by phylogenetic tree analysis. The promoter regions contain a large number of cis-acting elements relating to abiotic stresses, plant hormones, growth and development. Transcriptomic data of S. involucrata treated under pressures of 40 kPa, 70 kPa and 101 kPa indicated that the SiCHS genes were sensitive to pressure. The correlation analysis between the expression of SiCHS genes and flavonol content showed that the expression of SiCHS2, SiCHS5, SiCHS7 and SiCHS10 genes were strongly correlated with the flavonol content (P < 0.01, r > 0.80). The results of Quantitative Real-time PCR (qPCR) substantiated the transcriptome results, showing that the expression levels of the four SiCHS genes were significantly down-regulated under natural habitats (70 kPa) compared to the normal pressure. This study constitutes the initial and comprehensive elaboration of the details concerning the SiCHS family members and provides critical foundational data for the atmospheric pressure stress on S. involucrata.