PS Webinar Series: PhD Exit Webinar - The SWEET Journey from Source to Sink in Setaria viridis: The Role of Sugar Effluxers

Abstract - This research project investigates how photoassimilates moves from source leaves to other sink tissues that accumulate large amounts of carbohydrates. Many sinks such as stem and seeds/grains rely on the accumulation of sugars and starch during their development as they mature and become storage tissue. Phloem loading exports sugar from the source tissue which subsequently travels to sinks where phloem unloading occurs to support the development of that tissue. During this process, sugars need to cross membrane barriers which is mediated by both active and passive membrane transporters, which move sugars against or along a concentration gradient, respectively. This thesis focuses on a recently discovered group of plasma membrane transporters in plants, known as Sugars Will Eventually Exported Transporters (SWEETs). The role of SWEETs in the transport of sugars from source to sink is studied here in the C4 grass, Setaria viridis, a C4 model species, closely related to many important crops such as sugarcane, maize and sorghum.

In this presentation I will discuss the role SWEETs have in phloem loading, unloading and the post-phloem pathway. The expression profiles of SWEETs and other genes related to sugar metabolism in source and sink tissue will be presented, mined from publicly available RNAseq data and data generated by me. Metabolite profiles of these tissues will also be analysed to determine what SWEETs might be transporting in planta. Commercially made antibodies for Setaria SWEETs were used to perform immunolocalisation experiments in both source and sink tissues to examine their cellular localisation. Lastly, functional characterisation data using Xenopus laevis oocytes as a heterologous system will be shown to determine if Setaria SWEETs can transport glucose or sucrose, the most abundant sugars found in plants.

Biography - I grew up in Maitland which is part of the Hunter Valley, known for its wine region and bogans. After finishing school at Maitland Grossmann High School (right across the road from Maitland Gaol, that formerly housed Ivan Milat, a fun fact I tell people), I obtained a Bachelor of Biotechnology from The University of Newcastle in Newcastle, Australia, not Newcastle, England. I did my honours there too in Professor Chris Grof’s lab on SWEETs in Setaria as well. After that, I met up with Bob on a trip to Canberra to see if there was a possibility of doing my PhD in his lab. Unlike most other projects, I said I wanted to do these things in my project rather than Bob giving me a project and he bloody said yes. So, in 2016 I started my PhD in the Furbank Lab here at the ANU node of the CoE for Translational Photosynthesis (well I work on stuff more downstream of photosynthesis) at RSB. I continued studying Setaria SWEETs, bringing Bob back into working on sugar transporters, since his focus now is on photosynthesis.