ON THE COVER

In many plant leaves, starch is synthesized during the day and degraded at night to fuel growth and metabolism. Starch is degraded primarily by β-amylases, liberating maltose, but this activity is preceded by glucan phosphorylation and is accompanied by dephosphorylation. A glucan phosphatase family member, LIKE SEX4 1 (LSF1), binds starch and is required for normal starch degradation. Schreier et al. (pages 2169–2186) show that LSF1 does not dephosphorylate glucans, and that glucan binding, but not phosphatase activity, is required for the function of LSF1 in starch degradation. They propose that LSF1 binds β-amylases at the starch granule surface, thereby promoting starch degradation. The cover images show Arabidopsis rosettes harvested at the end of the night and stained for starch with iodine. The lightly stained plants are either wild type, lsf1 mutant complemented with LSF1, or lsf1 mutant complemented with LSF1 carrying a mutated phosphatase domain. The dark-stained plants are uncomplemented lsf1 mutants or lsf1 mutants complemented with LSF1 carrying a mutated starch binding domain: these plants incompletely degrade their starch during the night and thus accumulate excess starch.