Metallochaperone protein SaHIPP41 enhances cadmium tolerance and accumulation in the hyperaccumulator Solanum americanum

Soil cadmium (Cd) contamination is a major global environmental challenge. Solanum americanum , a Cd-hyperaccumulating plant, holds potential for application in phytoremediation. Although the heavy metal-associated isoprenylated plant protein (HIPP) family is known to play crucial roles in plant heavy metal accumulation and detoxification, its functions in S. americanum remain unclear. This study systematically identified 45 SaHIPP genes in S. americanum and, through evolutionary, collinearity, and expression-pattern analyses, selected the candidate gene SaHIPP41 , which was significantly induced by Cd stress. Heterologous expression in yeast demonstrated that SaHIPP41 enhances yeast Cd accumulation and sensitivity, a function dependent on its conserved CxxC domain. Subcellular localization analyses revealed that SaHIPP41 localizes to the cell membrane. Overexpression of SaHIPP41 in S. americanum significantly increased plant Cd accumulation and improved growth performance under Cd stress. Physiological analysis indicated that the overexpression lines exhibited higher activities of superoxide dismutase (SOD) peroxidase (POD). Transcriptome analysis revealed that SaHIPP41 overexpression regulates multiple pathways, including those involved in heavy metal transport, antioxidant metabolism, and photosynthesis. In summary, SaHIPP41 synergistically enhanced both Cd accumulation and tolerance in S. americanum through its dual role in promoting Cd accumulation and maintaining Cu homeostasis. These results provide novel insights into the role of plant HIPP genes in heavy metal detoxification and highlight a promising candidate for phytoremediation applications.