期刊
BMC PLANT BIOLOGY
卷 18, 期 -, 页码 -出版社
BMC
DOI: 10.1186/s12870-018-1303-8
关键词
Linum usitatissimum L.; Orbitides; Cyclolinopeptides; Plant genetic resources; Mass spectrometry; Sequencing
资金
- Total Utilization Flax GENomics (TUFGEN) project - Genome Canada [1309]
- Saskatchewan Flax Development Commission (SFDC)
- Saskatchewan Ministry of Agriculture - Agricultural Development Fund [20080205, 20120099, 20120146]
Background: Flaxseed orbitides are homodetic plant cyclic peptides arising from ribosomal synthesis and posttranslation modification (N to C cyclization), and lacking cysteine double bonds (Nat Prod Rep 30: 108-160, 2013). Screening for orbitide composition was conducted on the flax core collection (FCC) grown at both Saskatoon, Saskatchewan and Morden, Manitoba over three growing seasons (2009-2011). Two flax (Linum usitatissimum L.) accessions 'Hollandia' (CN 98056) and 'Z 11637' (CN 98150) produce neither [1-9-N alpha C]-linusorb B2 (3) nor [1-9-N alpha C]-linusorb B3 (1). Mass spectrometry was used to identify novel compounds and elucidate their structure. NMR spectroscopy was used to corroborate structural information. Results: Experimental findings indicated that these accessions produce a novel orbitide, identified in three oxidation states having quasimolecular ion peaks at m/z 1072.6 (18), 1088.6 (19), and 1104.6 (20) [M+ H](+) corresponding to molecular formulae C57H86N9O9S, C57H86N9O10S, and C57H86N9O11S, respectively. The structure of 19 was confirmed unequivocally as [1-9-NaC]-OLIPPFFLI. PCR amplification and sequencing of the gene coding for 18, using primers developed for 3 and 1, identified the putative linear precursor protein of 18 as being comprised of the first three amino acid residues of 3 (MLI), four conserved amino acid residues of 3 and/ or 1 (PPFF), and the last two residues of 1 (LI). Conclusion: Comparison of gene sequencing data revealed that a 117 base pair deletion had occurred that resulted in truncation of both 3 and 1 to produce a sequence encoding for the novel orbitide precursor of 18. This observation suggests that repeat units of flax orbitide genes are conserved and suggests a novel mechanism for evolution of orbitide gene diversity. Orbitides 19 and 20 contain MetO and MetO2, respectively, and are not directly encoded, but are products of post-translation modification of Met present in 18 ([1-9-N alpha C]-MLIPPFFLI).
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