Background

Quinolizidine alkaloids (QAs) are secondary metabolites that are adaptive characters unique to certain monophyletic groups, including the legume tribe Genisteae, which contains several Lupinus crop species. Lupin is a grain legume that thrives on nutrient deficient soils and can be used as an ecological pioneer for impoverished substrates, as well as being a high protein and fiber food source (Hane 2017, Li 2011). QAs are known to provide defense against pests, including aphids, which cause major yield losses and transmit various plant viruses (Frick 2017). Unfortunately, QA concentration in grain tissues used for food purposes must remain below the industry threshold of 0.02% (Frick 2017), which is often challenging because only a few genes, and even fewer proteins, associated with the biosynthetic pathways producing these compounds are known.

Figure 1 (Frick 2017), below, shows the QA biosynthetic pathway, with dotted lines representing the uncharacterized enzyme reactions. Meanwhile, figure 2 from MetaCyc shows the specific pathway for lupanine, one of the 8 major structural classes that QA can take. These figures illustrate how much still stands to be explored.

Inside the QA biosynthetic pathway, only a few proteins have been characterized, namely the DNA binding protein ethylene-responsive transcription factor 3 (EREBP-3), leucine zipper protein, and coronatine-insensitive 1, which has been theorized to provide clues about QA regulation (Bunsupa 2012). These proteins are mostly known in Lupinus albus, along with 13-hydroxylupanine O-tigloyltransferase (T., Okada. 2005). For this project, I plan to reference these proteins in resources like uniprot (The UniProt Consortium 2019), and explore if there are other similar sequences using BLAST. I will then use the Clustal tool (Madeira 2019) to compare the resulting file of proteins and visualize them, in order to check if there are other similar protein sequences and how far those similarities run, with the use of phylogenetic trees. The results from this study will give an overview of the four known proteins associated with the QA biosynthetic pathway and their similar sequences.