Fission yeast HMT1 lowers seed cadmium through phytochelatin-dependent vacuolar sequestration in Arabidopsis.
Much of our dietary uptake of heavy metals is through the consumption of plants. A long-sought strategy to reduce chronic exposure to heavy metals is to develop plant varieties with reduced accumulation in edible tissues. Here, we describe that the fission yeast (Schizosaccharomyces pombe) phytochelatin (PC)-cadmium (Cd) transporter SpHMT1 produced in Arabidopsis (Arabidopsis thaliana) was localized to tonoplast, and enhanced tolerance to and accumulation of Cd2+, copper, arsenic, and zinc. The action of SpHMT1 requires PC substrates, and failed to confer Cd2+ tolerance and accumulation when glutathione and PC synthesis was blocked by L-buthionine sulfoximine, or only PC synthesis is blocked in the cad1-3 mutant, which is deficient in PC synthase. SpHMT1 expression enhanced vacuolar Cd2+ accumulation in wild-type Columbia-0, but not in cad1-3, where only approximately 35% of the Cd2+ in protoplasts was localized in vacuoles, in contrast to the near 100% found in wild-type vacuoles and approximately 25% in those of cad2-1 that synthesizes very low amounts of glutathione and PCs. Interestingly, constitutive SpHMT1 expression delayed root-to-shoot metal transport, and root-targeted expression confirmed that roots can serve as a sink to reduce metal contents in shoots and seeds. These findings suggest that SpHMT1 function requires PCs in Arabidopsis, and it is feasible to promote food safety by engineering plants using SpHMT1 to decrease metal accumulation in edible tissues.
National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, People's Republic of China.
Jing
J
Huang
Yu
Y
Zhang
Jia-Shi
JS
Peng
Chen
C
Zhong
Hong-Ying
HY
Yi
David W
DW
Ow
Ji-Ming
JM
Gong
D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000222:Adaptation, Physiological / Q000187:drug effects; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D002104:Cadmium / Q000378:metabolism* / Q000633:toxicity; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009928:Organ Specificity / Q000187:drug effects; D054811:Phytochelatins / Q000494:pharmacology*; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000378:metabolism; D030821:Plants, Genetically Modified; D012568:Schizosaccharomyces / Q000187:drug effects / Q000378:metabolism*; D012639:Seeds / Q000187:drug effects / Q000378:metabolism*; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism*
D018528:ATP-Binding Cassette Transporters; D029681:Arabidopsis Proteins; C489670:hmt1 protein, S pombe; D002104:Cadmium; D019328:Buthionine Sulfoximine; D054811:Phytochelatins; D005978:Glutathione