HvVPE3, a gene closely associated with Cd uptake and tolerance in barley

Abstract

Cadmium (Cd) contamination in soils has become a serious issue of sustainable crop production and food safety. Here, HvVPE3, a γ-type VPE (vacuolar processing enzyme) gene, is firstly reported to regulate Cd uptake/tolerance. We isolated and functionally characterized HvVPE3 using genetic transformation coupled with physio-biochemical assay of Cd tolerance in barley. HvVPE3 was mainly expressed in leaves and being inducible by Cd stress. Subcellular localization verified that HvVPE3 is localized in the endoplasmic reticulum (ER). Silencing of HvVPE3 by RNA interfering (RNAi) significantly decreased Cd concentration in barley and improved tolerance to Cd stress, whereas HvVPE3 overexpression resulted in increased Cd concentration and hypersensitivity to Cd stress. Compared with the transformation-free wild-type (WT), HvVPE3-RNAi lines recorded significantly higher plant height and shoot biomass after two weeks 10 μM Cd exposure, but exhibited inhibited root net Cd2+ influx, suppressed Cd-induced increase in caspase-1, -8-like activities, and enhanced anti-oxidative activities such as catalase (CAT), peroxidase (POD), glutathione reductase (GR) and ascorbic acid oxidase (APX) thus mitigated Cd-induced oxidative stress and programmed cell death (PCD) to improve Cd tolerance in barley. Evolutionary bioinformatic confirms that VPE3s are highly conserved in green plants and may have evolved from the Order of Huperzia in Lycophytes. Our findings reveal a promising functional gene for breeding in developing barley varieties with low Cd accumulation and high Cd tolerance.