Plants under Attack: Discoveries That May Lead to Plants Better Able to Withstand Pathog

Receptors in the plasma membrane of plant cells are critical for recognizing pathogens, but how they get there is poorly understood. Dr.Sorina Popescu’s research could lead to strategies for manipulating the transport of receptors to the plant cell surface at various times before or after attack by pathogens. Altering immune receptor abundance at the cell membrane and other properties that influence the signaling competency of immune receptors may allow the engineering of plants that react faster and more efficiently to pathogens.

FLS2 (FLAGELIN-SENSITIVE2) is a plant receptor that recognizes flagellin, a conserved protein present in many pathogenic bacteria. Research reported in this paper shows that FLS2 binds to two proteins from the reticulon family, RTNLB1 and RTNLB2. Very little is known about the functions of the plant reticulon-like proteins. On the other hand, the animal reticulons have been studied extensively and are well known for their roles in the endoplasmic reticulum and in the intracellular trafficking of various proteins. Interestingly, a human reticulon was found to be an inhibitor of nervous tissue regeneration and there is evidence for the reticulons’ importance in neurodegenerative diseases such as Alzheimer’s disease.

The research further showed that in plants that lack both RTNLB1 and RTNLB2 or plants that overexpress RTNLB1, lower amounts of FLS2 accumulated at the plasma membrane and the plants were more susceptible to a bacterial pathogen. This suggests that in RTNLB transgenics, FLS2 cannot reach its plasma membrane destination and thus cannot activate the immune pathways that enable the plants to defend themselves against pathogens. Using Nicotiana benthamiana plants that co-expressed FLS2 and RTNLB1 it was further demonstrated that the newly synthesized FLS2 receptor molecules were trapped at a specific step on their route to the cell surface – the endoplasmic reticulum. Taken together, these results demonstrate that RTNLB1 and RTNLB2 are necessary for the intracellular transport of FLS2 to the plasma membrane.