Paulo Ferreira - A ROLE FOR THE SUBUNIT 7 OF THE ANAPHASE PROMOTING COMPLEX (APC7) IN THE PLANT IMMUNE SYSTEM RESPONSES

In contrast to animals, plant development is mostly postembryonic; during embryogenesis the main developmental event is the establishment of the root–shoot axis. Organ initiation and growth take place after germination, driven by cell division and differentiation at the meristems. Progression through the cell division cycle requires the temporal and spatial control by regulatory proteins in order to correctly duplicate the DNA and to deliver the newly duplicated genomes to the two daughter cells during mitosis. Cell cycle regulatory components most likely have a bifunctional role in plants. In addition to regulation of the cell cycle process itself, they are involved in the coordination of cell division in the context of a developing organism. Furthermore, at almost every cell cycle, dividing cells at the meristems must integrate development and environmental cues in order to decide whether to go on in another division cycle or to start a new developmental program. CDK/Cyclin activity regulates the transition through cell cycle checkpoints and thereby plant growth and development, and is itself under control of a variety of upstream modules. One of these is the Anaphase Promoting Complex (APC/C), which is an E3 ubiquitin ligase that controls CDK activity by mitosis-promoting cyclins. Besides the well recognized role of the APC during the mitotic cycle, there is increasing evidence that the APC plays a critical role during cell differentiation and development.Here, we show that ectopic expression of the C-terminus portion of the Arabidopsis APC7 subunit accelerates overall plant growth and results in plants with increased biomass production. In addition, the resulting plants are also tolerant to the CaLCuV geminivirus. These results indicate that the APC play active roles in regulation of plant growth and raise the intriguing possibility that the APC may mediate plant immune responses.