About the Cover
Tocopherols (vitamin E) have long been assumed to play essential roles in protecting plants from oxidative stress. Maeda et al. (pages 2710–2732) analyzed a series of Arabidopsis vitamin E (vte) biosynthetic mutants. Surprisingly, only minor differences were observed between a tocopherol-deficient vte2 mutant and the wild type during high-intensity light, salinity, and drought stresses. By contrast, vte mutants exhibited dramatic phenotypes in response to nonfreezing low temperatures, independently of any photoprotective functions of tocopherols. Further analysis suggested that the mutants were defective in phloem loading capacity. The study indicates that tocopherols play a more limited role in photoprotection than previously assumed but play a crucial role in lowtemperature adaptation and phloem loading. The cover shows a false colored image of phloem ultrastructure from cold-treated vte2 overlaid with a leaf stained with aniline blue for callose visualization. The mutant exhibits dramatic ultrastructural changes exclusively in phloem parenchyma transfer cells, a bottleneck of photoassimilate export. Cover image by Tammy L. Sage.
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Copyright © 2008 by the American Society of Plant Biologists
