Maternal effect genes, which affect the next generation when they are maternally inherited, are important in the early development of many animals. The maternal contribution to early plant development is less clear but maternal effects in plants have been attributed to the restricted expression of maternal alleles through genomic imprinting. Now, Frédéric Berger and colleagues report that, in Arabidopsis, the housekeeping gene DNA LIGASE 1 (AtLIG1), which mends DNA single-strand breaks, exerts a maternal effect on seed development by being involved in a pathway that controls imprinting (see p. ). They show that maternal inheritance of loss-of-function AtLIG1 mutations disrupts the development of the endosperm, the seed tissue that nurtures embryonic development. Additional experiments suggest that the maternal effect associated with mutant AtLIG1 could arise because AtLIG1 usually repairs the DNA single-strand breaks caused by DEMETER (DME), a DNA glycosylase that transcriptionally activates the maternal allele of imprinted genes by removing methylated cytosine residues. Whether similar events occur during imprinting in animals awaits further investigation.
