Phytoalexin and biomarker peptide detection using mass spectrometry

Abstract

Mass spectrometry (MS) has been one of the scientific techniques most commonly used in different areas. Therefore, the current research was carried out in order to investigate the role of MS in biological analysis. This study is divided into two main parts. The first part used MS imaging to reveal the ability of the technique for imaging metabolites directly from plant tissue. Thai rice varieties were used to investigate the production and distribution of diterpenoid phytoalexins using matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI). Results revealed the successfully detection of 5 types of diterpenoid phytoalexins on RD6 rice leaf tissue, including momilactone-A (m/z 353.17), momilactone-B (m/z 369.16), phytocassane-A/D/E (m/z 355.18), phytocassane-B (m/z 373.19) and phytocassane-C (m/z 357.20). In the second part, MS technique was used to assess the consequence of prolonged nicotine treatment on the invasion of A549 non-small cell lung cancer cell line by label-free quantitative proteomic analysis. Proteins were collected from both the monolayer and the invasion systems to investigate the alteration in protein expression. Fifty five proteins from the monolayer system and 100 proteins from the invasion system were identified with a change in expression level after prolonged nicotine treatment. Western blotting was then employed to validate the candidate proteins. The results indicated that prolonged exposure of nicotine promoted invasion on A549 cells. Interestingly, legumain, heat shock protein HSP 90-alpha, heat shock related 70 kDa protein 2, protein disulfide isomerase A3 and profilin-1 were found to show higher expression in A549 cells after prolonged exposure to nicotine. These findings testify to the power of mass spectrometry in biological molecule detection, allowing the discovery of novel information in the future.