Novel flax orbitide derived from genetic deletion.

Area of Science:

• Plant biochemistry
• Molecular genetics
• Natural product chemistry

Background:

• Flaxseed orbitides are cyclic peptides synthesized ribosomally and modified post-translationally.
• The flax core collection (FCC) was screened for orbitide composition over three growing seasons.
• Two flax accessions, 'Hollandia' and 'Z 11637', were found to lack known orbitides.

Purpose of the Study:

• To identify novel compounds in specific flax accessions.
• To elucidate the structure of newly identified flaxseed orbitides.
• To investigate the genetic basis for novel orbitide production.

Main Methods:

• Mass spectrometry (MS) was employed for novel compound identification and structural elucidation.
• Nuclear Magnetic Resonance (NMR) spectroscopy was used to confirm structural details.
• Polymerase Chain Reaction (PCR) amplification and sequencing were performed on the gene encoding the novel orbitide precursor.

Main Results:

• A novel orbitide was identified in three oxidation states with specific molecular formulae and quasimolecular ion peaks.
• The structure of one orbitide was confirmed as [1-9-NαC]-OLIPPFFLI.
• Gene sequencing revealed a 117 base pair deletion leading to a truncated precursor for the novel orbitide.

Conclusions:

• A 117 base pair deletion in flax orbitide genes results in truncation and production of a novel orbitide precursor.
• Conserved repeat units in flax orbitide genes suggest a novel mechanism for orbitide gene evolution.
• Orbitides 19 and 20 are post-translationally modified products of the novel orbitide precursor, containing oxidized methionine residues.