P-425 - The transcription factor MpGRAS7 is a novel susceptibility factor with a role in reproductive development in Marchantia

While it is known that vascular plants integrate biotic and abiotic signals for their development, knowledge of this in non-vascular plants is lacking. The transcription factor MpGRAS7 from the model bryophyte Marchantia polymorpha has recently been found to respond to abiotic stresses such as drought and far-red light. Furthermore, MpGRAS7 shifts the balance of reproductive strategy of M. polymorpha towards the sexual rather than asexual mode. Here we show that in addition to the responsiveness to abiotic signals, infection of Marchantia with the pathogen Phytophthora palmivora leads to increased systemic expression of MpGRAS7. Treatment of Marchantia with P. palmivora cell-free supernatant was sufficient to elicit a similar increase in expression, confirming that the causal agent is a molecule rather than infection structures. Knock-out mutants of MpGRAS7 in M. polymorpha and M. paleacea showed increased resistance to infection by P. palmivora,implicating MpGRAS7 as a susceptibility gene. MpGRAS7 therefore functions as a positive regulator of infection and is nevertheless maintained in Marchantia due to its role in coordinating reproductive development. Future work will determine the integration of these functions.