The evolution of a key family of transcription factors in the seeds of angiosperm plants

The identification of key regulatory transcription factors (TFs) involved in the maturation and germination of seeds has been an aim of our group (P.I. Prof. Pilar Carbonero) in the past years and a number of TF genes belonging to several TF families, such as bZIP, DOF and MYB have been demonstrated to be important in both processes. However, it is still unclear to what extent these TF genes are regulated in monocot- and dicotyledonous seeds. In this review paper, the AFL sub-family of B3 TFs (VP1/ABI3, FUS3, LEC2) has been explored and its origin, through the course of evolution, traced back to non-vascular plants such as Physcomitrella patens and its function explored taking into account expression patterns and interactions with other TFs. The first member of this family to be described was the maize Viviparous-1 (Vp-1) as a central player of Pre-Harvest Sprouting and as a regulator of the C1 gene encoding a MYB-like TF regulator of the anthocyanin biosynthesis pathway. Its orthologs from Arabidopsis (ABI3) and other cereals (barley HvVP1; wheat TaVP1, etc.) have been demonstrated to play essential roles in the regulation of Seed Storage Protein (SSP) and Late Embryogenesis Abundant (LEA) protein genes upon maturation. The functional role of VP1/ABI3 and that of FUS3 and LEC2 during seed embryogenesis, the dormancy-germination transition, post-germination storage reserve mobilization and ABA signaling has been also discussed (see Figure).