botanyone
The mechanisms involved in plant defence against pathogens are of considerable scientific and agricultural interest. Novák et al. use activation of the gene ipt to produce high levels of cytokinins in tobacco, Nicotiana tabacum, and find that this is sufficient to trigger fast cell death without intervening chlorosis, which is characteristic of the hypersensitive response. The results are consistent with the suggestion that the molecular processes underpinning this hypersensitive-like response are orchestrated by increases in cellular hydrogen peroxide levels. The hypersensitive-like response includes inhibition of photosynthesis, increases in stress hormone levels, oxidative damage to membranes and stomatal closure. Thus, cytokinins may act as signals and/or mediate plant defences against pathogen attack.
