Analysis of growth-physiological changes and NAC gene family response in Fallopia multiflora under salt stress

• An elevation in salt concentration is accompanied by a downward trend in the overall growth of F. multiflora . • F. multiflora proline content rises incrementally with salt concentration. • Eighty-three NAC gene family members are identified in F. multiflora. • FmNAC51 and FmNAC70 show a significant negative correlation with THSG. Soil salinization represents a paramount abiotic stressor that impedes agricultural sustainability and land resource utilization globally. Investigating the salt tolerance of the medicinal plant F. multiflora is therefore imperative for expanding its adaptive cultivation to fulfill market demands. This research systematically delineates, for the first time, the multifaceted regulatory impact of salt stress on F. multiflora , encompassing morphological development, physiological and biochemical parameters, the accumulation of secondary metabolites, and the expression of pivotal enzyme genes in the stilbene glycoside biosynthetic pathway. A concurrent genome-wide analysis of the NAC transcription factor family, a key regulator of abiotic stress responses, was also conducted. Findings indicated that escalating salt concentrations generally suppressed growth metrics but progressively elevated osmolyte content, such as proline. Stilbene glycoside accumulation exhibited organ-specific dynamics: in stems, most treatments triggered an initial decline followed by an increase, whereas in roots, a pattern of increase preceding decrease was predominant. The expression of critical THSG biosynthetic genes was significantly altered. Furthermore, 83 FmNAC genes were identified, with genomic duplication events serving as the principal mechanism for family expansion. The promoters of these genes harbored abundant cis-elements responsive to light, hormones, and stress, and most FmNACs demonstrated tissue-specific expression. Correlation analyses reveal that FmNAC51 and FmNAC70 exhibit a negative correlation with THSG content. Conversely, FmNAC14 displays a positive association with proline, while potentially exerting a detrimental influence on diverse growth metrics, such as leaf fresh weight and chlorophyll content. The FmNAC transcription factors may act on the key enzyme genes involved in stilbene glycoside biosynthesis. This study elucidates significant alterations in the growth and development of F. multiflora under salt stress and implies that the FmNAC gene family may be involved in these regulatory processes. The outcomes provide a potential theoretical foundation for future functional characterization of salt-responsive genes and could offer insights for devising strategies to cultivate F. multiflora in saline-affected regions.