Early responses of cultured tobacco BY-2 cells to boron deprivation

Abstract

Boron (B) cross-links pectic polysaccharides at rhamnogalacturonanII regions and thereby contributes to building the supramolecular cell wall structure. However, it remains unknown how B deficiency, and probably the resulting aberrant cell wall structure, triggers physiological changes and brings about cell death. To understand this mechanism, we have analyzed the early responses of cultured tobacco BY-2 cells to B deprivation.
When tobacco BY-2 cells were transferred to a B-free medium, salicylate-inducible stress genes were upregulated within 30 minutes, whereas jasmonate-inducible ones were downregulated. These changes were suppressed by removing Ca²⁺ from the medium or supplementing the medium with La³⁺, a Ca²⁺ channel blocker. Analysis using aequorin-transformed cells revealed that cells deprived of B took up more Ca²⁺ than control. These results show that the absence of B from the medium rapidly causes an opening of Ca²⁺ channels.