High‐throughput MALDI‐MSI metabolite analysis of plant tissue microarrays

A novel metabolomics analysis technique, termed matrix‐assisted laser desorption/ionization mass spectrometry imaging‐based plant tissue microarray (MALDI‐MSI‐PTMA), was successfully developed for high‐throughput metabolite detection and imaging from plant tissues. This technique completely overcomes the disadvantage that metabolites cannot be accessible on an intact plant tissue due to the limitations of the special structures of plant cells (e.g. epicuticular wax, cuticle and cell wall) through homogenization of plant tissues, preparation of PTMA moulds and matrix spraying of PTMA sections. Our study shows several properties of MALDI‐MSI‐PTMA, including no need of sample separation and enrichment, high‐throughput metabolite detection and imaging (>1000 samples per day), high‐stability mass spectrometry data acquisition and imaging reconstruction and high reproducibility of data. This novel technique was successfully used to quickly evaluate the effects of two plant growth regulator treatments (i.e. 6‐benzylaminopurine and N‐phenyl‐N′‐1,2,3‐thiadiazol‐5‐ylurea) on endogenous metabolite expression in plant tissue culture specimens of Dracocephalum rupestre Hance (D. rupestre). Intra‐day and inter‐day evaluations indicated that the metabolite data detected on PTMA sections had good reproducibility and stability. A total of 312 metabolite ion signals in leaves tissues of D. rupestre were detected, of which 228 metabolite ion signals were identified, they were composed of 122 primary metabolites, 90 secondary metabolites and 16 identified metabolites of unknown classification. The results demonstrated the advantages of MALDI‐MSI‐PTMA technique for enhancing the overall detection ability of metabolites in plant tissues, indicating that MALDI‐MSI‐PTMA has the potential to become a powerful routine practice for high‐throughput metabolite study in plant science.