The cover shows a rice deficiency mutant in local auxin biosynthesis. In this issue, Guo et al. (581–600) report a rice tsg1 mutant which has more tillers but a smaller panicle and grain size resulting from a reduction in endogenous auxin. TSG1 encodes a tryptophan aminotransferase localized at the endoplasmic reticulum with remarkable aminotransferase activity. TSG1 dominates the tryptophan aminotransferase family of rice, playing a prominent role in local auxin biosynthesis.