E2FA is a major transcription factor controlling the mitotic cycle and the endocycle in nematode-induced feeding sites

Abstract

Plant host cell-cycle hyperactivation is essential for nematode feeding site (NFS) ontogenesis, but the balanced mitotic and endoreplication cycles must occur for homeostasis. Alterations in core cell cycle gene expression are well known to disturb root-knot and cyst-NFS development. Herein, our investigation focused on the activity of E2FA and E2FB transcription factors in root-knot nematode-induced galls in Arabidopsis thaliana controlling both the mitotic and endocycles through the activation of S-phase cell cycle genes. The roles of the two plant E2F activators during cell cycle progression in galls were compared with syncytia induced by cyst nematodes. E2FA and E2FB transcripts were highly expressed in both galls and syncytia. Loss-of-function analysis revealed that the absence of E2FA and E2FB impaired feeding-site development, resulting in significantly reduced gall development and nematode reproduction. Transcript analysis of galls upon E2FA and E2FB loss-of-function compared with that of wild-type revealed differential expression of selected target genes operating during S phase. Although our results imply the functional interplay of E2FA and E2FB for gall development, we recognize that E2FA alone commands and sustains cell division as well as the endocycle in galls and syncytia, whereas E2FB is likely partaking in nematode-induced gall initiation.