The 30th International Conference on Arabidopsis Research (ICAR 2019)

504 / 2019-03-01 18:37:59

Helical hairpin peptides are buried in seed storage vicilin precursors

pumpkin, macadamia, vicilins

Plenary track > Metabolism

An unusual evolutionary mechanism observed recently is for peptides to evolve within an existing protein. The first example was a group of small, cyclic peptides matured by proteolytic processing of the precursors for seed storage albumin. Another group of peptides have also been observed within precursors for seed storage vicilin (known as 7S globulin). However, the evidence for vicilin buried peptides (VBPs) was limited in seeds of pumpkin and macadamia. Here, we searched sequences for vicilin precursors in GenBank and UniprotKB and found that VBPs buried the amino-terminal region of preprovicilins in species from Amborellales to eudicots. It suggested that VBPs are widespread and truly ancient. Using liquid chromatography, tandem mass spectrometry and (for one gene) PCR, we identified the first protein evidence for monocot VBP in date palm seeds and evidence from other crops including tomato, sesame and pumpkin relatives, cucumber and the sponge loofah. The structure of VBPs was confirmed as a helical hairpin fold stapled by two internal disulfide bonds using NMR solution. Our findings suggest that the family is large and ancient and the age and evolutionary retention of this peptide family indicates they have important roles in plant biology.