Metabolomics and hormonomics to crack the code of filbert growth

Plants respond to changes in their environments through hormonal activation of a physiological cascade that redirects metabolic resources and growth. In filberts (Corylus sp.), chelated iron promotes the growth of new shoots but the mechanism(s) are not understood.

To use untargeted metabolomics and hormonomics approaches to generate novel hypotheses for the morphoregulatory role of ferric ethylenediamine-N,N'-di-(ortho-hydroxyphenyl) acetic acid (Fe-EDDHA) in filbert shoot organogenesis in vitro.

Data were generated using previously optimized standardized untargeted metabolomics protocols with time of flight mass spectrometry. Multivariate statistical tools (principal component and partial least squares discriminant analysis) did not detect significant differences. Discovery tools Significance Analysis of Microarrays (SAM), multiple linear regression analysis, Bayesian analysis, logical algorithms, machine learning, synthetic biotransformations, targeted hormonomics, and online resources including MetaboAnalyst were used.

Starch/sucrose metabolism and shikimate pathway metabolites were increased. Dose dependent decreases were found in polyphenol metabolism, specifically ellagic acid and its methylated derivative 3,4,3'-tri-O-methylellagic acid. Hormonomics analysis revealed significant differences in phytohormones and their conjugates. FeEDDHA treatment reduced indole-3-acetic acid, abscisic acid, salicylic acid, jasmonic acid conjugates (JA-Trp, JA-Ile, OH-JA) and dihydrozeatinglucoside in regenerating explants. Serotonin (5HT) was decreased in FeEDDHA-treated regenerating tissues while the related metabolite melatonin was increased. Eight phenolic conjugates of 5HT and eight catabolites were affected by FeEDDHA indicating that metabolism to sequester, deactivate and metabolize 5HT was induced by Fe(III). Tryptophan was metabolized through kynurenine but not anthranilate.

Seven novel hypotheses were generated to guide future studies to understand the regulatory control(s) of shoot organogenesis.