Thermographic visualization of cell death in tobacco and Arabidopsis

Pending cell death was visualized by thermographic imaging in bacterio-opsi n transgenic tobacco plants, Cell death in these plants was characterized b y a complex lesion phenotype, Isolated cell death lesions were preceded by a colocalized thermal effect, as previously observed at sites infected by t obacco mosaic virus (TMV) (Chaerle et al. 1999 Nature Biotechnology 17, 813 -816). However, in most cases, a coherent front of higher temperature, trai led by cell death, initiated at the leaf base and expanded over the leaf la mina. In contrast to the homogenous thermal front, cell death was first vis ible close to the veins, and subsequently appeared as discrete spots on the interveinal tissue, as cell death spread along the veins. Regions with vis ible cell death had a lower temperature because of wafer evaporation from d amaged cells. In analogy with previous observations on the-localized tobacc o-TMV interaction (Chaerle et al. 1999), the kinetics of thermographic and continuous gas exchange measurements indicated that stomatal closure preced ed tissue collapse, Localized spontaneous cell death could also be presympt omatically visualized in the Arabidopsis lsd2 mutant.