Exploring the functions of Ded1/DDX3 proteins in plants

DEAD-box RNA helicases of the Ded1/DDX3 sub-family are essential regulators of cellular proteostasis. The functions of these proteins have been extensively studied in mammals and yeast. In these organisms, Ded1/DDX3 proteins play key roles in both canonical and non-canonical translation initiation and translation-related processes. Moreover, they also participate in different processes related to RNA metabolism. Plant homologues, although less studied, have revealed both conserved and unique functions compared with other eukaryotes. Members of this sub-family in plants play important roles in plant defence by regulating translation initiation of upstream open reading frames associated with stem loops situated downstream of their start codons during immune activation, as well as in loading small RNAs into extracellular vesicles. Additionally, these proteins have been associated with abiotic stress adaptation and with non-sense-mediated RNA decay, although the functional relevance of the latter remains unclear. This review provides an overview of the current knowledge about the structure, biochemical, and biological functions of Ded1/DDX3 sub-family members in both plant and non-plant eukaryotes, highlighting the peculiarities of plant Ded1/DDX3 members, and the major gaps that remain in understanding this protein sub-family in plants.