Silicon fertilization of potato: expression of putative transporters and tuber skin quality.

MAIN CONCLUSION: A silicon transporter homolog was upregulated by Si fertilization and drought in potato roots and leaves. High Si in tuber skin resulted in anatomical and compositional changes suggesting delayed skin maturation. Silicon (Si) fertilization has beneficial effects on plant resistance to biotic and abiotic stresses. Potatoes, low Si accumulators, are susceptible to yield loss due to suboptimal growth conditions; thus Si fertilization may contribute to crop improvement. The effect of Si fertilization on transcript levels of putative transporters, Si uptake and tuber quality was studied in potatoes grown in a glasshouse and fertilized with sodium silicate, under normal and drought-stress conditions. Anatomical studies and Raman spectroscopic analyses of tuber skin were conducted. A putative transporter, StLsi1, with conserved amino acid domains for Si transport, was isolated. The StLsi1 transcript was detected in roots and leaves and its level increased twofold following Si fertilization, and about fivefold in leaves upon Si × drought interaction. Nevertheless, increased Si accumulation was detected only in tuber peel of Si-fertilized plants--probably due to passive movement of Si from the soil solution--where it modified skin cell morphology and cell-wall composition. Compared to controls, skin cell area was greater, suberin biosynthetic genes were upregulated and skin cell walls were enriched with oxidized aromatic moieties suggesting enhanced lignification and suberization. The accumulating data suggest delayed tuber skin maturation following Si fertilization. Despite StLsi1 upregulation, low accumulation of Si in roots and leaves may result from low transport activity. Study of Si metabolism in potato, a major staple food, would contribute to the improvement of other low Si crops to ensure food security under changing climate.