About the Cover
On the Cover: Plant cells can respond to microbial
pathogens with a complex multitude of defense reactions, among which is
the formation of phytoalexins, antimicrobial secondary compounds. Roos
et al. (pp. 349-364) report on the formation of benzophenanthridine alkaloids in cells of Californian poppy that can be triggered independent of the hypersensitive response, and thus allows insights into a selected part of the signaling mechanism. A transient
acidification of the cytoplasm appears to be an essential step of the
signal chain between elicitor contact and alkaloid formation, thus
emphasizing the role of 
pH as a second messenger. Confocal pH
imaging indicates that the shifts of cytoplasmic and nuclear pH are
most probably brought about by a transient efflux of vacuolar
protons.
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Copyright © 2008 by the American Society of Plant Biologists
