Characterization of the Heavy-Metal-Associated Isoprenylated Plant Protein (HIPP) Gene Family from Triticeae Species

Abstract

Heavy-metal-associated (HMA) isoprenylated plant proteins (HIPPs) only exist in vascular plants. They play important roles in responses to biotic/abiotic stresses, heavy-metal homeostasis, and detoxification. However, research on the distribution, diversification, and function of <i>HIPPs</i> in <i>Triticeae</i> species is limited. In this study, a total of 278 <i>HIPPs</i> were identified from a database from five <i>Triticeae</i> species, and 13 were cloned from <i>Haynaldia villosa</i>. These genes were classified into five groups by phylogenetic analysis. Most HIPPs had one HMA domain, while 51 from Clade I had two, and all <i>HIPPs</i> had good collinear relationships between species or subgenomes. In silico expression profiling revealed that 44 of the 114 wheat <i>HIPPs</i> were dominantly expressed in roots, 43 were upregulated under biotic stresses, and 29 were upregulated upon drought or heat treatment. Subcellular localization analysis of the cloned <i>HIPPs</i> from <i>H. villosa</i> showed that they were expressed on the plasma membrane. <i>HIPP1-V</i> was upregulated in <i>H. villosa</i> after Cd treatment, and transgenic wheat plants overexpressing <i>HIPP1-V</i> showed enhanced Cd tolerance, as shown by the recovery of seed-germination and root-growth inhibition by supplementary Cd. This research provides a genome-wide overview of the <i>Triticeae HIPP</i> genes and proved that <i>HIPP1-V</i> positively regulates Cd tolerance in common wheat.