Analysis of MAPK singnaling pathway in the lethality of interspecific Nicotiana hybrid using MEK mutants

Abstract

Cultured cell (GTH4) of Nicotiana gossei x N. tabacum dies at 26C, but not at 37C. After the shift from 37C to 26C, burst of H₂O₂ and activation of SIPK were observed in the cells. However, these were suppressed by U0126, an inhibitor of MEK, and cell death was delayed as well. This suggests that MAPK signaling is involved in the hybrid lethality. To further analyze a role of MAPK signaling, the F₁ hybrids between N. gossei and the transgenic tobacco harboring NtMEK2^DD or NtMEK2^KR, the constitutively active or -inactive MEK inducible with dexamethasone (DEX). The cell lines, GTH^DD and GTH^KR, were generated from the hybrid seedlings. Both lines showed high viability of cell at 37C, but died at 26C under the control condition. However, cell death of GTH^KR at 26C was suppressed by DEX treatment. This suggests that overproduction of NtMEK2^KR disturbed MAPK signaling and, eventually, suppressed cell death.