CMDH4 encodes a protein that is required for lead tolerance in Arabidopsis

Background and aims Lead (Pb) is one of the most dangerous soil pollutants with high toxicity to plants and animals. However, the molecular mechanisms behind Pb tolerance are poorly understood. Here we identified a previously unknown cytosol-localized malate dehydrogenase (designated as CMDH4), which is involved in regulating Pb tolerance in Arabidopsis. Methods T-DNA insertional mutants and overexpression lines were used for functional analysis. Lead was externally supplied and phenotypic analysis of these plants was performed. Results CMDH4 transcription was induced by Pb stress. Loss-of-function of CMDH4 resulted in reducedNAD(P) H level, and Pb hypersensitivity in response to Pb stress. Further analysis revealed that internal H2O2. concentration and cellular damage was elevated in cmdh4 mutants. External supply of NAD(P) H could improve plant tolerance to Pb stress, and recover the sensitivity of cmdh4 loss-of-function mutants to the wild-type level. In addition, the transcription level of PDR12 coding for a Pb2+ pump was significantly reduced in cmdh4 mutants, thereby leading to increased Pb accumulation. Conclusions To sum up, our data provide evidence that CMDH4 is required for lead tolerance and reduced Pb accumulation in Arabidopsis.